Importance of antioxidants for humans 

Antioxidants are high value biochemical compounds found in tomatoes in very high concentrations and play an unequalled role in fight against oxidation process which may result in cellular damage or death [19]. Lycopene is an effective antioxidant and used as fortified nutritional supplement [20]. Its amount in the tomato fruit can be increased by applying pulse light treatment to tomato, with wavelengths of emitted spectrum ranging from UVC to infrared (180-1100 nm) and for several minutes [21], and also by adding yeast and bacterial genes in case of transgenic varieties. Antioxidant compounds play an important role to prevent the oxidation of oxidizable products [22], and also have an impact on the protective system of the body in response to Reactive Oxygen Species (ROS), that are hazardous by-products produced during normal aerobic cellular respiration [23]. Tomato sauce can be a good source for the intake of antioxidants [24]. Results from clinical studies showed that regular intake of lycopene can reduce the risk of various types of cancers of vital human organs like prostate, lung and stomach [25] as well as reduces the risk of a life threatening medical conditions like coronary heart and  kidney diseases [26]. Antioxidants also play a vital role in prevention of Ischemic brain stroke disease [27]. Antioxidants have become very sort after component of cosmetics industries especially natural antioxidants taken from seaweed are very demanding and popular in the beauty industry [28]. Antioxidants can donate electrons to stabilize ROS and to prevent their detrimental effects, including both endogenous (are synthesized within body and by the body itself) and exogenous molecules (those which are from external sources to the body)[29]. Consumption of fruit-based antioxidants are found to be helpful for patients suffering from bowel disease [30]. Research has confirmed that many diseases like diabetes, different kind of cancers, Parkinson’s disease, cardiovascular diseases [31] and Alzheimer’s diseases are highly interrelated with cellular redox and free disproportion [32] and to maintain homeostatic balance in the human body as well as to achieve the prevention and cure of diseases, the consumption of antioxidants in our daily life has become necessary [33]. Most importantly flavonoids play vital role in curing the disease like Atherosclerosis by providing anti-inflammatory properties and due to this reason flavonoids should be an integral part of the human daily diet. Such defensive factors might also include fibres, trace minerals, and many other micronutrients which include many of the vitamins, pro-vitamins and various other compounds that have chemical properties of antioxidants [34]. It is hypothesized that various factors in the changing diet of migrants are related to increased risk of cancer that may include food-based carcinogens and various other cancer-promoting elements like high levels of body fats [35]. Many antioxidants have been described to exert numerous advantageous effects on human health that include antiviral, anti-cancer, cardio-protective, antibacterial, anti-inflammatory and neuro-protective properties [36-38]. Including fruits and vegetables in your diet can increase volume of antioxidants in the blood stream up to significant level [39]. It has been proposed that a reduced amount of antioxidant activity in the cell can result into elevated risk of cancer that is why the ingestion of antioxidants can be helpful to prevent carcinogenesis [40]. Tomato is a nutrient-condensed food that offers a wide range of benefits to various bodily systems. Nutrients present in the tomato are beneficial for healthy skin, weight loss and for cardiac health. Tomatoes having high antioxidant contents should be included in the diet because it can help to protect human body against cancers, maintain normal blood pressure and decrease the levels of blood glucose in diabetic patents [41]. It is estimated that 35% of the deaths occurring in the USA due to cancer are related to poor diet. Therefore, dietary modification is a practical strategy to prevent the chronic diseases in human. The real aim of Recommended Dietary Allowances (RDA) has been shifted from prevention of clinical deficiencies to be focused on the prevention of diseases such as birth defects, coronary heart disease and cancer [40]. Although the concentration of carotenoids is less in tomato as compared to the other vegetables, none the less, tomato stands among the top vegetables as a source of vitamin A, E and C due to its high consumption all over the world.  Although tomato is a rich source of many nutrients, secondary metabolites, organic acids and vitamins etc. but it is important that after picking tomato should be consumed as early as possible because after detachment from the plant they continue to ripen and reach a point where the quality deteriorate to an extinct to render them useless for consumption. Interestingly according to latest findings the antioxidants are also known to be very effective in the treatment of hypertensive patients of Grade I & II with no reported side effects [42]. One tomato fruit can provide approximately 20% of vitamin A and 40% of the recommended daily intake of vitamin-C [43]. The removal of the fruit skin is very detrimental, as it has been found that by removing the tomato peal can result in the loss of 80% lycopene, 63% of phenolic compounds and 57% of β-carotene[44].

Importance of antioxidants in plants

Antioxidants greatly delay or reduce the oxidative stressors in plants [45]. These antioxidants are produced in vivo, i.e., superoxide dismutase (SOD) and decreased glutathione (GSH) etc. or utilized as diet based antioxidants [45]. Various plants have been known as a source of dietary antioxidants. It is estimated that almost two-third of global plant species are of some medicinal value and almost all these plants produce antioxidants [46]. The importance of the exogenous plant antioxidants was first highlighted with the finding and extraction of ascorbic acid in plants. Presently there are about 19 in-vitro and 10 in-vivo approaches of estimating antioxidant contents in plants [47]. Mostly in-vitro methods have been reported to show strong antioxidant activity in plants. This may be due to their unique ability to produce non-enzyme antioxidant substances like AsA and glutathione, in addition to secondary metabolites like phenolic complexes as shown in figure-1. Researcher have found that in a plant cell, chloroplast and mitochondria are the key power-generators, as well as sites of ROS production. Similarly, peroxisomes are known to be 3rd most prominent site for the synthesis of ROS, i.e., hydrogen peroxide (H2O2), superoxides (O2-) and nitricoxides (NO). Likewise ROS, other compounds like reactive nitrogen species (RNS) like nitric oxides (NO) are also produced in different cell organelles that include chloroplast, mitochondria and peroxisome [48]. These free-radicals are constantly synthesized in plant cells due to genetics or in response to stress as signaling molecule [49,50]. The over synthesis of these free-radicals in plants can lead to damaged DNA, cellular protein and lipids. The antioxidant response is considered to be a very important process in the protection of plants against oxidative damage which is caused by a great number of environmental factors such as light, climate, salinity, temperature, and nutritional deprivation etc. [51]. Among these factors, the oxidative stress is apparently the main cause of membrane damage and changing the composition and contents of antioxidant compounds that results in the overall change in antioxidant activity of the tissue [52]. Increased activity of antioxidant pathway is one of the main mechanisms found to be involved in the resistance against stresses like chilling, heat, drought, salinity and wounds. Antioxidant defense system in tomato can be strengthen by delaying biosynthesis processes through the application of selenium [53] and bio-augmented compost [54].  During the days of peak durations of solar radiation and in extreme cold weather, plants are forced to develop a defensive mechanism against the ultraviolet (UV) radiation and extreme production of free radicals by internal accumulation of antioxidant substances [55]. A detailed stress perception and antioxidant defense mechanism in plants is shown in Figure-1. Tomato is one of the most commonly consumed fresh as well as processed vegetables around the globe for its nutritional value and bioactive antioxidants such as phytosterols  [56], carotenoids, phenolics and vitamins C and E [11]. It is reported that some cultivars of tomato have more percentage of phenolic compounds than other widely grown varieties. The Portuguese ex-situ conserved germplasm of tomato is prominent for its high antioxidant concentrations [57].

Cultural and molecular approaches to enhance antioxidants in tomato

Followings are the pre-harvest and post-harvest techniques through which antioxidant contents can be increased in tomatoes.

Aeroponics:

This is the process of growing plants in a medium without soil, but roots are kept suspended and sprayed with water or nutrient solution [58]. Fruit bearing tomato plants were grown in a controlled environment under LED with light intensity of 250 μmolm-2s-1 at the top of plant canopy. Five plants were planted per meter square (m^-2). Temperature was kept between 25°C±3 during the light period and during the dark period, temperature was maintained at 18°C±3. The CO2 level was the same as the outside atmosphere. The modified Hoagland nutrient solution was the basic culture medium. The architecture of aeroponic system was designed so that it can be easily fitted within the top of the growth trays. The system included two misters spaced at 20cm intervals. Misters were angled downwards to ensure coverage of the plants roots throughout the entire growth cycle. Excessive aeroponic water was collected at the bottom of the slightly angled channel and flows out back to the petal reservoir. Tomato seeds were germinated at 24ᵒC for days and then tomato seedlings were transplanted to the aeroponic system. The activity of the two important antioxidants i.e., peroxidase and catalase were measured in tomato leaves at ontogenesis. It was observed that during early leaf development, POD and CAT activity increased and reached its maximum values at the development stage while decreased later at leaf senescence. Also, those plants that were grown in porous tube vermiculite condition throughout the leaf development showed low levels of enzymatic antioxidant activity. Similarly, higher lycopene contents were noted in aeroponics grown tomatoes as compared to vermiculate based apparatus. No significant change in beta-carotene contents was observed among both these treatments [58]. A graphical representation of an aeroponics system is shown in Figure-2.

Application of salicylic acid

Healthy, uniform and matured green tomatoes were harvested, washed, and dried. Salicylic acid treatment with 4+1, 4+2, 4+4 mM concentration were applied through plant foliar method three weeks prior to the harvest. After harvest fruits were dipped for five minutes in salicylic acid solution for five minutes. Treated and non-treated tomato fruits were stored at 10֯ C with relative humidity between 85-90% for 10-40 days respectively. Vitamin C or ascorbic acid contents were measured using titrimetric method and result was expressed in mg/100g [59]. ). After 40 days of storage it was observed that the treated tomatoes with pre and post-harvest treatment of salicylic acid contain more ascorbic acid contents as compared to the normal tomatoes and results were significant (p<0.001) [60]. A diagrammatic representation of this approach is shown in figure 3.

Application of Trichoderma enriched bio-fertilizer in soil

Antioxidants present in tomato are very useful in preventing cardiovascular diseases. Application of bio-fertilizer has significantly increased lycopene and vitamin c contents of tomato. Seeds were collected to grow, and land was prepared having the seedbed size of 2.5×5.0m. First the nursery was grown and for the protection of seeds from rain and excessive fog the polythene bags were used after the 25 days. Healthy seedlings were transplanted with a spacing of 50×50 cm [61]. ). It was ensured that Trichoderma enriched biofertilizer was prepared by well reputed agriculture enterprise as bio-fertilizer having good quality cow dung, poultry litter, household/kitchen waste and press mud of sugar mills in its constituents. In this technique, 6 treatments were used. T1 was controlled (without NPK and Bio-F), T2 was recommended dose of NPK, T3 was 100% Bio-Fertilizer, T4 was 75% Bio-Fertilizer +25%N, T5 was 50% Bio-Fertilizer +50%N, T6 was 25% Bio-Fertilizer+75%N and recommendable dose of phosphorus and potassium was used in last 3 treatments (Figure-4). And NPK contained TSP (triple superphosphate), urea and MOP (muriate of potash) and a full dose of all these comprised the bio-fertilizer at the final preparation of land. Nitrogen was applied in 3 splits. Ripened tomatoes were harvested, weigh and expressed in kg per plant. Beta-carotene and lycopene were measured at spectrophotometer (Hitachi no. 200-20, Hitachi, Japan) by using method described by [62]. According to observations, the ascorbic acid was increased under the treatment of 100% bio-fertilizer (T3) and beta-carotene was increased under T4 (75% Bio-Fertilizer+25% N) whereas enhanced lycopene contents were observed in case of T2 (recommended dose of NPK). These results proved that quantity and function of antioxidant in tomato were greatly enhanced due to the application of bio-fertilizer [40].

Freeze drying

In this procedure the tomatoes were first cut into slices having size of 1×1cm2 and spread on the steel tray and then dried in a freeze drier at the vacuum pressure of 0.1333 mbar for 24 hours at -50° Celsius [63]. The extract of aqueous sample for the determination of antioxidant capacity was prepared according to the already optimized protocol [21] where 3ml of 75% methanol was added to 0.5-1g sample of tomato slices and sonicated for 15 min and later sample was centrifuged for 10 min at 2500rpm to collect the supernatant. Then 75% (3ml) of methanol was added to pellet and procedure was repeated to make the final volume of 10 ml and both supernatants were combined. It was observed that GSH, cysteine, total phenolic compound and CUPRAC values were increased by this freezing drier method [64]. Hence by keeping tomatoes in cool environment can significantly increase antioxidants levels in fruit [65].

Exposure of tomatoes to infrared light at green stage

Freshly picked first fruits from the first truss were placed on plastic tray (42 fruits per each tray) and covered with aluminum foil to ensured that fruits were not in contact with each other. Trays were stored in custom built climate chamber for 20 days in the first experiment and for 14 days in second experiment under the constant day/night temperature (20°C/19°C) and relative humidity (RH 75%-85%). In experiment # 1, the effect of duration of red light radiation on the accumulation of health promoting compounds was noted [66]. Whereas in experiment # 2 the effect of continuous or intermittent red light was measured on the accumulation of health promoting compound. In both of these experiments tomatoes of the control treatment were kept in dark (having same RH and temperature).  For red light treatment tomatoes were irradiated with light emitting diode (LED) module which was installed in the climate chamber [67] [68]. The experimental settings were controlled by equipment specific software. Tomatoes undergone this process required five less days to reach the same maturity levels. Moreover, this exposure raised concentrations of lycopene, total flavonoids, phenolics and β-carotene in the cut fruit sections. The light treatments method proved to be simple and environmentally safe technique to improve the health-promoting antioxidants.

Metabolite engineering

The metabolic engineering in plants involved various biochemical and genetic modification techniques to enhance the expression of several phytonutrients, enzymes and genes in tomato fruit. Ascorbic acid (Vitamin-C) is a vital dietary phytonutrient required to perform major metabolic processes in human body [69]. To enhance the ascorbic acid (AsA) production in tomato, scientists overexpressed the genes associated with ascorbate recycling enzymes DHAR and MDHAR. The green and ripened fruit of resulting transgenic lines showed 1.6-fold increase in AsA levels thus enhancing its nutritional value. β-carotene and lycopene are well-known for being beneficial for human health. When a carotenoid (crtl) gene of bacterial origin was transformed in tomato, an increase of 3-fold (45%) of β-carotene level was observed in transgenic lines [70]. Folate is a vital nutrient and its deficiency in humans can cause many neurological and physical defects and diseases. In biological system the folate is synthesized from p-amino-benzoate (PABA). Plant scientists managed to increase the level of folate in tomato fruit by 25 folds by overexpressing the amino-deoxychorismate-synthase which is 1st enzyme of PABA pathway [71]. Beta-carotene is also a precursor for Vitamin-A, and a powerful antioxidant. When a lycopene B-cyclase gene from flowering plant daffodil was transformed in chloroplast of tomato, more than 50% increased β-carotene contents was observed in transgenic tomato plants [72]. Other studies involving antioxidant enhancements showed that when a Vitis vinifera L. stilbene synthase (StSy) gene was overexpressed in tomato plant, the transgenic plants relatively accumulated more transresveratrol, resulting in much higher contents of glutathione and ascorbate which are vital soluble antioxidants involved in crucial metabolic activities in humans [73]. In the effort to improve the dietary value of tomato fruit scientist have utilized unique techniques like RNA interference (RNAi). Attempts were made to suppress an endogenous photo-morphogenesis gene (DET-1) in tomato fruit with the help of RNAi technology. Resulting transgenic plant indeed contained degraded DET-1 expression while consequently an impressive increase in both flavonoid and β-carotenoid contents was observed thus improving the nutritional value of genetically modified tomato [74].

In addition to the advanced metabolic and genome editing and engineering techniques, many researchers have also adopted conventional breeding techniques to improve antioxidant contents of tomato fruit. The detail of the approaches adopted, specific technologies used, and genes/pathways improved are described in Table-1.

Omics approaches

With the introduction of various omics approaches in plant sciences, exceptional advancements have been made in study of signaling pathways involved in beneficial metabolites synthesis across diverse species. Omics approaches such as genomics, transcriptomics, miRNAomics, proteomics, and metabolomics have changed the landscape of different diseases including stroke, diabetes, and cancer. Genomic approaches such as genome wide association studies have led to the identification of 30 loci, which were used in establishing relationship among body mass index and the risk of obesity [1].

Transplastomic tomato plants possessing LCYB gene from daffodil plant were engineered using biolistic gene gun. The results showed that introduction of a single gene of β-carotenoid biosynthetic pathway in diverse tomato genotypes induced considerable metabolic modifications in carotenoid, apo-carotenoid and phyto-hormonal pathways resulting in up to 77 percent yield increase and improvement in fruit’s vitamin-A contents [2]. During fruit maturing, lycopene accumulation inhabits the production of cyclical carotenoids. Fruit-targeted over-expression of lycopene-beta-cyclase (LCYb) lead to enhanced beta-carotene (pro-vitamin-A) contents in tomato fruit [3]. Carotenoid biosynthetic pathway regulation and limitations in its accumulation in the fruit are not yet fully understood. Apel and Bock, 2009 [4] over-expressed the lycopene-beta-cyclase genes from Narcissus pseudonarcissus in the tomato chloroplast. It was also observed that expression of plant-based gene was able to synthesis lycopene better that the one having bacterial origin. the conversion rate of lycopene into beta-carotene was noted at 1mg/g of dry weight that is almost 50% increase in total beta-carotenoid in the transplastomic tomato.

Micro-RNAs are small (19 to 24 base pair long) non-coding RNA units that can strongly alter gene expression. By binding with their target mRNA these short RNA fragments can cause cleavage at specific translational sites hence, disrupting the gene expression. Lab based studies have shown that tomato-based lycopene are alimentary anti-cancerous agents. Lycopene is known to alter testosterone metabolism in the body. Testosterone plays key role in prostate cancer development through the activation of androgen bio-signaling pathway. The study showed that the miRNA expression was down-regulated in transgenic TRAMP mice in comparison to wild-type mice in initial prostate cancer stage while lycopene played minimum roles in this process [5]. Xu et al. (2010) [6] also reported the regulation of fruit-based carotenoids by miRNAs. He revealed 51 known and 9 new differentially expressing miRNAs from a sweet orange mutant through genome sequencing. Among these TC5 gene was found to encode lycopene beta-cyclase (LYC-b), a rate-limiting enzyme in the conversion of lycopene to downstream cyclic carotenes. Koul et al. (2016) [7] during a comparative study found key regulatory genes linked with carotenoid biosynthesis that include mi-R1911, mi-R482, mi-R172, mi-R396, mi-R395, osa-mi-R169i-5p.2, and ppt-mi-R1027a.

During fruit maturity, beta-carotenoid accumulation not only decide the level of antioxidant levels but also its colors and shelf life. For decades the plant breeders are deploying concerted efforts in order to improve on these particular traits in tomato fruit. the evidence from past studies have shown a strong relation between CYCB gene expression and color development in fruit. Similar work has identified a single mutation in SGR sequence that hinders chlorophyll depletion thus resulting in retention of brown color in a few tomato varieties. By crossing orange KNY2 and brown KNB1 tomato genotypes, the scientists were able to produce a novel orange brown F2 generation. This orange-brown fruit possessed higher beta-carotene and chlorophyll contents than the parental lines. Such studies have proven to be very helpful for the plant breeders in order to develop tomato varieties have desirable fruit color with added benefits of enhanced beta-carotene and antioxidants [8].

Some less utilized techniques for antioxidant improvement

Following are some additional but less known methods of improving health promoting antioxidants that were developed and tested for enhancing the health benefits of tomato:

1. Steam cooking [103].
2. Addition of herbs while cooking [104].

Bioavailability of antioxidants for absorption

Tomato and its by-products are the richest source of lycopene for humans as its fruit contains a significant number of beneficial antioxidants such as phenolic flavonoid and ascorbic acid etc. However, it is observed that in fresh tomatoes the anti-oxidants components greatly vary with type of cultivars, growth conditions, harvesting time and temperature. By measuring the concentration of plasma and urine after ingestion of tomatoes as whole or in a processed form, the bioavailability of some carotenoids including phenolic compounds have been described here.

Fruit sampling and in-vitro digestion

Tomatoes fruit from three commercial tomatoes cultivar were used in study which is mostly used for the fresh consumption. Tomatoes were grown hydroponically on a commercial green house and harvested at red ripe stage. The modified method of miller was used to study the in vitro digestion of tomatoes. The method consisted of a pepsin-HCl digestion for 2 hours, followed by a pancreatin digestion with bile salt for further 2 hours at 37°C. After the completion of in vitro digestion, total phenolic, flavonoid, lycopene, ascorbic acid and antioxidant activities in the fresh tomatoes as well as in the digestion extracts and residual tomatoes solids was analyzed. In-vitro digestion can cause a serious amount of decrease in antioxidant activity up to 75% even in fried form [105].

Measurement of total phenolics

Total phenolics was measured by using the Folin-Ciocalteau method. Hydrophilic, Lipophilic and Digestion extracts were properly diluted with 2.5ml freshly diluted 0.2M Folin-Ciocalteau reagent. By adding 2ml of 75% w/v Na₂CO₃ reaction was neutralized, samples were vortexed for 20 sec then incubated at 45°C for the 15 min and resulting absorbance of blue color was measured at 765nm on UV-visible recording spectrometer. Gallic acid was used as standard and result was expressed as Gallic acid equivalents. The total phenolic results were corrected for the contribution of ascorbic acid [56].

Measurement of lycopene

1. Ilahy R, Hdider C, Lenucci MS, Tlili I, Dalessandro G. Phytochemical composition and antioxidant activity of high-lycopene tomato (Solanum lycopersicum L.) cultivars grown in Southern Italy. Scientia Horticulturae, (2011); 127(3): 255-261.
2. Jez M, Wiczkowski W, Zielinska D, Bialobrzewski I, Blaszczak W. The impact of high pressure processing on the phenolic profile, hydrophilic antioxidant and reducing capacity of puree obtained from commercial tomato varieties. Food Chem, (2018); 261201-209.
3. Katırcı N, Işık N, Güpür Ç, Guler HO, Gursoy O, et al. Differences in antioxidant activity, total phenolic and flavonoid contents of commercial and homemade tomato pastes. Journal of the Saudi Society of Agricultural Sciences, (2020); 19(4): 249-254.
4. Szabo K, Dulf FV, Diaconeasa Z, Vodnar DC. Antimicrobial and antioxidant properties of tomato processing byproducts and their correlation with the biochemical composition. Lwt, (2019); 116.
5. Abushita AA, Daood HG, Biacs PA. Change in carotenoids and antioxidant vitamins in tomato as a function of varietal and technological factors. Journal of Agricultural and Food Chemistry, (2000); 48(6): 2075-2081.
6. Bogale A, Nagle M, Latif S, Aguila M, Müller J. Regulated deficit irrigation and partial root-zone drying irrigation impact bioactive compounds and antioxidant activity in two select tomato cultivars. Scientia Horticulturae, (2016); 213115-124.
7. Martínez-Valverde I, Periago MJ, Provan G, Chesson A. Phenolic compounds, lycopene and antioxidant activity in commercial varieties of tomato (Lycopersicum esculentum). Journal of the Science of Food and Agriculture, (2002); 82(3): 323-330.
8. Tigist M, Workneh TS, Woldetsadik K. Effects of variety on the quality of tomato stored under ambient conditions. Journal of Food Science and Technology, (2013); 50(3): 477-486.
9. Figas MR, Prohens J, Raigon MD, Fita A, Garcia-Martinez MD, et al. Characterization of composition traits related to organoleptic and functional quality for the differentiation, selection and enhancement of local varieties of tomato from different cultivar groups. Food Chemistry, (2015); 187517-524.
10. Coyago-Cruz E, Corell M, Moriana A, Hernanz D, Benitez-Gonzalez AM, et al. Antioxidants (carotenoids and phenolics) profile of cherry tomatoes as influenced by deficit irrigation, ripening and cluster. Food Chemistry, (2018); 240: 870-884.
11. Pernice R, Parisi M, Giordano I, Pentangelo A, Graziani G, et al. Antioxidants profile of small tomato fruits: Effect of irrigation and industrial process. Scientia Horticulturae, (2010); 126(2): 156-163.
12. Del Giudice R, Raiola A, Tenore GC, Frusciante L, Barone A, et al. Antioxidant bioactive compounds in tomato fruits at different ripening stages and their effects on normal and cancer cells. Journal of Functional Foods, (2015); 18: 83-94.
13. Muthukumarasamy R, Amran N, Ilyana A, Radhakrishnan D. Comparison of Antioxidant Activity in the Methanolic Peels Extracts of Solanum lycopersocum and Solanum lycopersocum Var. Cerasiforme. International Journal of Pharmaceutical and Clinical Research, (2017); 9(04): 298-301.
14. Park C-Y, Kim Y-J, Shin Y. Effects of an ethylene absorbent and 1-methylcyclopropene on tomato quality and antioxidant contents during storage. Horticulture, Environment, and Biotechnology, (2016); 57(1): 38-45.
15. D'Introno A, Paradiso A, Scoditti E, D'Amico L, De Paolis A, et al. Antioxidant and anti-inflammatory properties of tomato fruits synthesizing different amounts of stilbenes. Plant Biotechnology Journal, (2009); 7(5): 422-429.
16. Raiola A, Rigano MM, Calafiore R, Frusciante L, Barone A. Enhancing the health-promoting effects of tomato fruit for biofortified food. Mediators of Inflammation, (2014); 2014139873.
17. Campestrini LH, Melo PS, Peres LEP, Calhelha RC, Ferreira I, et al. A new variety of purple tomato as a rich source of bioactive carotenoids and its potential health benefits. Heliyon, (2019); 5(11): e02831.
18. Adalid AM, Roselló S, Nuez F. Evaluation and selection of tomato accessions (Solanum section Lycopersicon) for content of lycopene, β-carotene and ascorbic acid. Journal of Food Composition and Analysis, (2010); 23(6): 613-618.
19. Forman HJ, Davies KJ, Ursini F. How do nutritional antioxidants really work: nucleophilic tone and para-hormesis versus free radical scavenging in vivo. Free Radic Biol Med, (2014); 6624-35.
20. ÜStÜNdaŞ M, Yener HB, Helvaci ŞŞ. Parameters Affecting Lycopene Extraction from Tomato Powder and Its Antioxidant Activity. Anadolu University Journal of Science and Technology-A Applied Sciences and Engineering, (2018); 1-1.
21. Valdivia-Nájar CG, Martín-Belloso O, Soliva-Fortuny R. Kinetics of the changes in the antioxidant potential of fresh-cut tomatoes as affected by pulsed light treatments and storage time. Journal of Food Engineering, (2018); 237: 146-153.
22. Gurbuz Colak N, Eken NT, Ulger M, Frary A, Doganlar S. Mapping of quantitative trait loci for antioxidant molecules in tomato fruit: Carotenoids, vitamins C and E, glutathione and phenolic acids. Plant Science, (2020); 292: 110393.
23. Sulaiman M. An Overview of Natural Plant Antioxidants: Analysis and Evaluation. Advances in Biochemistry, (2013); 1(4): 64-72.
24. Tomas M, Beekwilder J, Hall RD, Sagdic O, Boyacioglu D, et al. Industrial processing versus home processing of tomato sauce: Effects on phenolics, flavonoids and in vitro bioaccessibility of antioxidants. Food Chemistry, (2017); 220: 51-58.
25. Vallecilla-Yepez L, Ciftci ON. Increasing cis-lycopene content of the oleoresin from tomato processing byproducts using supercritical carbon dioxide. LWT Food Science and Technology, (2018); 95354-360.
26. Ried K, Fakler P. Protective effect of lycopene on serum cholesterol and blood pressure: Meta-analyses of intervention trials. Maturitas, (2010); 68: 299-310.
27. Ullah khan W. Prevalence, Causes, Treatment and the Role of Antioxidants in Ischemic Brain Stroke Diseases: A Review. American Journal of Biomedical and Life Sciences, (2015); 3(2): 29-32.
28. Jacobsen C, Sorensen AM, Holdt SL, Akoh CC, Hermund DB. Source, Extraction, Characterization, and Applications of Novel Antioxidants from Seaweed. Annu Rev Food Sci Technol, (2019); 10: 541-568.
29. Desai C. Antioxidants: Fascinating and Favourable Biomolecules for Humans. Science Innovation, (2015); 3(6): 113-116.
30. Moura FA, de Andrade KQ, Dos Santos JCF, Araujo ORP, Goulart MOF. Antioxidant therapy for treatment of inflammatory bowel disease: Does it work? Redox Biology, (2015); 6: 617-639.
31. Sacco A, Raiola A, Calafiore R, Barone A, Rigano MM. New insights in the control of antioxidants accumulation in tomato by transcriptomic analyses of genotypes exhibiting contrasting levels of fruit metabolites. BMC Genomics, (2019); 20(1): 43.
32. Li S, Chen G, Zhang C, Wu M, Wu S, et al. Research progress of natural antioxidants in foods for the treatment of diseases. Food Science and Human Wellness, (2014); 3(3-4): 110-116.
33. Melendez-Martinez AJ, Fraser PD, Bramley PM. Accumulation of health promoting phytochemicals in wild relatives of tomato and their contribution to in vitro antioxidant activity. Phytochemistry, (2010); 71(10): 1104-1114.
34. González-Chavira MM, Herrera-Hernández MG, Guzmán-Maldonado H, Pons-Hernández JL. Controlled water deficit as abiotic stress factor for enhancing the phytochemical content and adding-value of crops. Scientia Horticulturae, (2018); 234: 354-360.
35. Silva-Beltran NP, Ruiz-Cruz S, Cira-Chavez LA, Estrada-Alvarado MI, Ornelas-Paz Jde J, et al. Total Phenolic, Flavonoid, Tomatine, and Tomatidine Contents and Antioxidant and Antimicrobial Activities of Extracts of Tomato Plant. International Journal of Analytical Chemistry, (2015); 284071.
36. Galano A, Mazzone G, Alvarez-Diduk R, Marino T, Alvarez-Idaboy JR, et al. Food Antioxidants: Chemical Insights at the Molecular Level. Annu Rev Food Sci Technol, (2016); 7335-352.
37. Patanè C, Malvuccio A, Saita A, Rizzarelli P, Siracusa L, et al. Nutritional changes during storage in fresh-cut long storage tomato as affected by biocompostable polylactide and cellulose based packaging. LWT – Food Science and Technology, (2019); 101: 618-624.
38. Ross J, Kasum C. Dietary flavonoids: Bioavailability, metabolic effects, and safety. Annual review of nutrition, (2002); 22: 19-34.
39. Tawfik MS. Antioxidants in Fig (Ficus carica L.) and their Effects in the Prevention of Atherosclerosis in Hamsters. Journal of Food and Nutrition Sciences, (2014); 2(4): 138-145.
40. Borguini RG, Bastos DHM, Moita-Neto JM, Capasso FS, Torres EAFdS. Antioxidant potential of tomatoes cultivated in organic and conventional systems. Brazilian Archives of Biology and Technology, (2013); 56(4): 521-529.
41. Bhandari SR, Cho M-C, Lee JG. Genotypic variation in carotenoid, ascorbic acid, total phenolic, and flavonoid contents, and antioxidant activity in selected tomato breeding lines. Horticulture, Environment, and Biotechnology, (2016); 57(5): 440-452.
42. Sorriento D, De Luca N, Trimarco B, Iaccarino G. The Antioxidant Therapy: New Insights in the Treatment of Hypertension. Frontiers in Physiology, (2018); 9: 258.
43. Ochoa Velasco CE, Guerrero-Beltran J. The effects of modified atmospheres on prickly pear (Opuntia albicarpa) stored at different temperatures. Postharvest Biology and Technology, (2016); 111: 314-321.
44. Vinha AF, Barreira SV, Costa AS, Alves RC, Oliveira MBP. Organic versus conventional tomatoes: Influence on physicochemical parameters, bioactive compounds and sensorial attributes. Food and chemical toxicology, (2014); 67: 139-144.
45. Halliwell B. Biochemistry of oxidative stress. Biochemical society transactions, (2007); 35(5): 1147-1150.
46. Krishnaiah D, Sarbatly R, Nithyanandam R. A review of the antioxidant potential of medicinal plant species. Food and bioproducts processing, (2011); 89(3): 217-233.
47. Alam MN, Bristi NJ, Rafiquzzaman M. Review on in vivo and in vitro methods evaluation of antioxidant activity. Saudi pharmaceutical journal, (2013); 21(2): 143-152.
48. Møller IM, Jensen PE, Hansson A. Oxidative modifications to cellular components in plants. Annual Review of Plant Biology, (2007); 58: 459-481.
49. Zhao J, Davis LC, Verpoorte R. Elicitor signal transduction leading to production of plant secondary metabolites. Biotechnology advances, (2005); 23(4): 283-333.
50. Mittler R. Oxidative stress, antioxidants and stress tolerance. Trends in plant science, (2002); 7(9): 405-410.
51. Sidhu V, Nandwani D, Wang L, Wu Y. A Study on Organic Tomatoes: Effect of a Biostimulator on Phytochemical and Antioxidant Activities. Journal of Food Quality, (2017); 20171-8.
52. Sharma P, Jha AB, Dubey RS, Pessarakli M. Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions. Journal of Botany, (2012); 20: 121-26.
53. Zhu Z, Chen Y, Shi G, Zhang X. Selenium delays tomato fruit ripening by inhibiting ethylene biosynthesis and enhancing the antioxidant defense system. Food Chemistry, (2017); 219: 179-184.
54. Verma S, Sharma A, Kumar R, Kaur C, Arora A, et al. Improvement of antioxidant and defense properties of Tomato (var. Pusa Rohini) by application of bioaugmented compost. Saudi Journal of Biological Sciences, (2015); 22(3): 256-264.
55. Chandra HM, Ramalingam S. Antioxidant potentials of skin, pulp, and seed fractions of commercially important tomato cultivars. Food Science and Biotechnology, (2011); 20(1): 15-21.
56. Liao P, Chen X, Wang M, Bach TJ, Chye ML. Improved fruit alpha-tocopherol, carotenoid, squalene and phytosterol contents through manipulation of Brassica juncea 3-Hydroxy-3-Methylglutaryl-COA Synthase1 in transgenic tomato. Plant Biotechnology Journal, (2018); 16(3): 784-796.
57. Pinela J, Montoya C, Carvalho AM, Martins V, Rocha F, et al. Phenolic composition and antioxidant properties of ex-situ conserved tomato (Solanum lycopersicum L.) germplasm. Food Research International, (2019); 125108545.
58. Wang M, Dong C, Gao W. Evaluation of the growth, photosynthetic characteristics, antioxidant capacity, biomass yield and quality of tomato using aeroponics, hydroponics and porous tube-vermiculite systems in bio-regenerative life support systems. Life Sciences in Space Research, (2019); 22: 68-75.
59. Mandal D, Pautu L, Hazarika T, Nautiyal BP, Shukla AC. Effect of Salicylic Acid on Physico-chemical Attributes and Shelf Life of Tomato Fruits at Refrigerated Storage. International Journal of Bio-resource & Stress Management, (2016); 7: 1272-1278.
60. Baninaiem E, Mirzaaliandastjerdi AM, Rastegar S, Abbaszade K. Effect of pre- and postharvest salicylic acid treatment on quality characteristics of tomato during cold storage. Advances in horticultural science, (2016); 30183-192.
61. Khan MY, Haque MM, Molla AH, Rahman MM, Alam MZ. Antioxidant compounds and minerals in tomatoes by Trichoderma-enriched biofertilizer and their relationship with the soil environments. Journal of Integrative Agriculture, (2017); 16(3): 691-703.
62. Dudas A. Fruit Quality of Tomato Affected by Single and Combined Bioeffectors in Organically System. Pakistan Journal of Agricultural Sciences, (2017); 54(04): 827-836.
63. Gumusay OA, Borazan AA, Ercal N, Demirkol O. Drying effects on the antioxidant properties of tomatoes and ginger. Food Chemistry, (2015); 173: 156-162.
64. Azeez L, Adebisi SA, Oyedeji AO, Adetoro RO, Tijani KO. Bioactive compounds’ contents, drying kinetics and mathematical modelling of tomato slices influenced by drying temperatures and time. Journal of the Saudi Society of Agricultural Sciences, (2019); 18(2): 120-126.
65. Nkolisa N, Magwaza LS, Workneh TS, Chimphango A, Sithole NJ. Postharvest quality and bioactive properties of tomatoes (Solanum lycopersicum) stored in a low-cost and energy-free evaporative cooling system. Heliyon, (2019); 5(8): e02266.
66. Pataro G, Sinik M, Capitoli MM, Donsì G, Ferrari G. The influence of post-harvest UV-C and pulsed light treatments on quality and antioxidant properties of tomato fruits during storage. Innovative Food Science & Emerging Technologies, (2015); 30: 103-111.
67. Panjai L, Noga G, Fiebig A, Hunsche M. Effects of continuous red light and short daily UV exposure during postharvest on carotenoid concentration and antioxidant capacity in stored tomatoes. Scientia Horticulturae, (2017); 226: 97-103.
68. Panjai L, Noga G, Hunsche M, Fiebig A. Optimal red light irradiation time to increase health-promoting compounds in tomato fruit postharvest. Scientia Horticulturae, (2019); 251: 189-196.
69. Haroldsen VM, Chi-Ham CL, Kulkarni S, Lorence A, Bennett AB. Constitutively expressed DHAR and MDHAR influence fruit, but not foliar ascorbate levels in tomato. Plant Physiology and Biochemistry, (2011); 49(10): 1244-1249.
70. Römer S, Fraser PD, Kiano JW, Shipton CA, Misawa N, et al. Elevation of the provitamin A content of transgenic tomato plants. Nature Biotechnology, (2000); 18(6): 666-669.
71. Hossain T, Rosenberg I, Selhub J, Kishore G, Beachy R, et al. Enhancement of folates in plants through metabolic engineering. Proceedings of the National Academy of Sciences of the United States of America, (2004); 101(14): 5158-5163.
72. Apel W, Bock R. Enhancement of carotenoid biosynthesis in transplastomic tomatoes by induced lycopene-to-provitamin A conversion. Plant Physiology, (2009); 151(1): 59-66.
73. Giovinazzo G, D'Amico L, Paradiso A, Bollini R, Sparvoli F, et al. Antioxidant metabolite profiles in tomato fruit constitutively expressing the grapevine stilbene synthase gene. Plant Biotechnology Journal, (2005); 3(1): 57-69.
74. Nonaka S, Arai C, Takayama M, Matsukura C, Ezura H. Efficient increase of -aminobutyric acid (GABA) content in tomato fruits by targeted mutagenesis. Scientific Reports, (2017); 7(1): 7057.
75. Zhang C, Liu J, Zhang Y, Cai X, Gong P, et al. Overexpression of SlGMEs leads to ascorbate accumulation with enhanced oxidative stress, cold, and salt tolerance in tomato. Plant Cell Reports, (2011); 30(3): 389-398.
76. Cronje C, George GM, Fernie AR, Bekker J, Kossmann J, et al. Manipulation of L-ascorbic acid biosynthesis pathways in Solanum lycopersicum: elevated GDP-mannose pyrophosphorylase activity enhances L-ascorbate levels in red fruit. Planta, (2012); 235(3): 553-564.
77. Díaz de la Garza RI, Gregory JF, Hanson AD. Folate biofortification of tomato fruit. Proceedings of the National Academy of Sciences, (2007); 104(10): 4218-4222.
78. Davuluri GR, van Tuinen A, Fraser PD, Manfredonia A, Newman R, et al. Fruit-specific RNAi-mediated suppression of DET1 enhances carotenoid and flavonoid content in tomatoes. Nature Biotechnology, (2005); 23(7): 890-895.
79. Butelli E, Titta L, Giorgio M, Mock HP, Matros A, et al. Enrichment of tomato fruit with health-promoting anthocyanins by expression of select transcription factors. Nature Biotechnology, (2008); 26(11): 1301-1308.
80. Adato A, Mandel T, Mintz-Oron S, Venger I, Levy D, et al. Fruit-surface flavonoid accumulation in tomato is controlled by a SlMYB12-regulated transcriptional network. PLoS Genetics, (2009); 5(12): e1000777.
81. D'Ambrosio C, Stigliani AL, Giorio G. CRISPR/Cas9 editing of carotenoid genes in tomato. Transgenic Research, (2018); 27(4): 367-378.
82. Wang Y, Luo Z, Lu C, Zhou R, Zhang H, et al. Transcriptome profiles reveal new regulatory factors of anthocyanin accumulation in a novel purple-colored cherry tomato cultivar Jinling Moyu. Plant Growth Regulation, (2018); 87(1): 9-18.
83. Chen L, Yang D, Zhang Y, Wu L, Zhang Y, et al. Evidence for a specific and critical role of mitogen-activated protein kinase 20 in uni-to-binucleate transition of microgametogenesis in tomato. New Phytologist, (2018); 219(1): 176-194.
84. Li R, Li R, Li X, Fu D, Zhu B, et al. Multiplexed CRISPR/Cas9-mediated metabolic engineering of gamma-aminobutyric acid levels in Solanum lycopersicum. Plant Biotechnology Journal, (2018); 16(2): 415-427.
85. Cermak T, Baltes NJ, Cegan R, Zhang Y, Voytas DF. High-frequency, precise modification of the tomato genome. Genome Biology, (2015); 16232.
86. Li X, Wang Y, Chen S, Tian H, Fu D, et al. Lycopene Is Enriched in Tomato Fruit by CRISPR/Cas9-Mediated Multiplex Genome Editing. Frontiers in Plant Science, (2018); 9559.
87. Mazzucato A, Papa R, Bitocchi E, Mosconi P, Nanni L, et al. Genetic diversity, structure and marker-trait associations in a collection of Italian tomato (Solanum lycopersicum L.) landraces. Theoretical and Applied Genetics, (2008); 116(5): 657-669.
88. Kinkade M, Foolad M. Validation and fine mapping of lyc12.1, a QTL for increased tomato fruit lycopene content. TAG Theoretical and applied genetics Theoretische und angewandte Genetik, (2013); 126.
89. Sun Y, Joachimski MM, Wignall PB, Yan C, Chen Y, et al. Lethally hot temperatures during the Early Triassic greenhouse. Science, (2012); 338(6105): 366-370.
90. Di Matteo A, Sacco A, Anacleria M, Pezzotti M, Delledonne M, et al. The ascorbic acid content of tomato fruits is associated with the expression of genes involved in pectin degradation. BMC plant biology, (2010); 10(1): 1-11.
91. Sacco A, Di Matteo A, Lombardi N, Trotta N, Punzo B, et al. Quantitative trait loci pyramiding for fruit quality traits in tomato. Molecular Breeding, (2013); 31(1): 217-222.
92. Ashrafi H, Kinkade MP, Merk HL, Foolad MR. Identification of novel quantitative trait loci for increased lycopene content and other fruit quality traits in a tomato recombinant inbred line population. Molecular Breeding, (2012); 30(1): 549-567.
93. Capel C, Fernández del Carmen A, Alba JM, Lima-Silva V, Hernández-Gras F, et al. Wide-genome QTL mapping of fruit quality traits in a tomato RIL population derived from the wild-relative species Solanum pimpinellifolium L. Theoretical and Applied Genetics, (2015); 128(10): 2019-2035.
94. Sun YD, Liang Y, Wu JM, Li YZ, Cui X, et al. Dynamic QTL analysis for fruit lycopene content and total soluble solid content in a Solanum lycopersicum x S. pimpinellifolium cross. Genetics and Molecular Research, (2012); 11(4): 3696-3710.
95. Kimbara J, Ohyama A, Chikano H, Ito H, Hosoi K, et al. QTL mapping of fruit nutritional and flavor components in tomato (Solanum lycopersicum) using genome-wide SSR markers and recombinant inbred lines (RILs) from an intra-specific cross. Euphytica, (2018); 214(11): 210.
96. Rousseaux MC, Jones CM, Adams D, Chetelat R, Bennett A, et al. QTL analysis of fruit antioxidants in tomato using Lycopersicon pennellii introgression lines. Theoretical and Applied Genetics, (2005); 111(7): 1396-1408.
97. Fei Z, Joung J-G, Tang X, Zheng Y, Huang M, et al. Tomato Functional Genomics Database: a comprehensive resource and analysis package for tomato functional genomics. (2010); 39(suppl_1): D1156-D1163.
98. Alba R, Payton P, Fei Z, McQuinn R, Debbie P, et al. Transcriptome and selected metabolite analyses reveal multiple points of ethylene control during tomato fruit development. Plant Cell, (2005); 17(11): 2954-2965.
99. Sim S-C, Durstewitz G, Plieske J, Wieseke R, Ganal MW, et al. Development of a large SNP genotyping array and generation of high-density genetic maps in tomato. PLOS one. (2012); 7(7): e40563.
100. Cherif AO, Trabelsi H, Ben Messaouda M, Kâabi B, Pellerin I, et al. Gas Chromatography−Mass Spectrometry Screening for Phytochemical 4-Desmethylsterols Accumulated during Development of Tunisian Peanut Kernels (Arachis hypogaea L.). Journal of Agricultural and Food Chemistry, (2010); 58(15): 8709-8714.
101. del Castillo MD, Martinez-Saez N, Amigo-Benavent M, Silvan JM. Phytochemomics and other omics for permitting health claims made on foods. Food Research International, (2013); 54(1): 1237-1249.
102. Iswari RS, Susanti R. Antioxidant activity from various tomato processing. Biosaintifika: Journal of Biology & Biology Education, (2016); 8(1): 129-134.
103. Beltrán Sanahuja A, De Pablo Gallego SL, Maestre Pérez SE, Valdés García A, Prats Moya MS. Influence of Cooking and Ingredients on the Antioxidant Activity, Phenolic Content and Volatile Profile of Different Variants of the Mediterranean Typical Tomato Sofrito. Antioxidants, (2019); 8(11): 551.
104. García-Hernández J, Hernández-Pérez M, Peinado I, Andrés A, Heredia A. Tomato-antioxidants enhance viability of L. reuteri under gastrointestinal conditions while the probiotic negatively affects bioaccessibility of lycopene and phenols. Journal of Functional Foods, (2018); 431-7.
105. Sun G, Chi W, Zhang C, Xu S, Li J, et al. Developing a green film with pH-sensitivity and antioxidant activity based on к-carrageenan and hydroxypropyl methylcellulose incorporating Prunus maackii juice. Food hydrocolloids, (2019); 94345-353.