Nutraceutical Characterization of Anthocyanin-Rich Fruits Produced by “Sun Black” Tomato Line

Abstract

Tomato ( Solanum lycopersicum L.) is one of the most cultivated vegetable in the world and it represents a large source of bioactive compounds, including carotenoids and polyphenols (phenolic acids and flavonoids). However, the concentration of flavonoids in tomato is considered sub-optimal, particularly because anthocyanins are not generally present. Therefore, this crop has been the object of an intense metabolic engineering in order to obtain anthocyanin-enriched tomatoes by using either breeding or transgenic strategies. Some wild tomato species, such as S. chilense and S. cheesmaniae , biosynthesize anthocyanins in the fruit sub-epidermal tissue, and some alleles from those genotypes have been introgressed into a new developed purple tomato line, called “Sun Black” (SB). It is a tomato line with a purple skin color, both in green and in red fruit stages, due to the biosynthesis of anthocyanins in the peel, and a normal red color pulp, with a taste just like a traditional tomato. SB is the result of a breeding programme and it is not a genetically modified (GM) product. We report the chemical characterization and structure elucidation of the attractive anthocyanins found in the peel of SB tomato, as well as other bioactive compounds (carotenoids, polyphenols, vitamin C) of the whole fruit. Using one- and two-dimensional NMR experiments, the two main anthocyanins were identified to be petunidin 3- O -[6″- O -(4 ‴ - O - E - p- coumaroyl-α-rhamnopyranosyl) -β-glucopyranoside]-5- O -β-glucopyranoside (petanin) and malvidin 3- O -[6″- O -(4 ‴ - O - E - p- coumaroyl-α-rhamnopyranosyl)-β-glucopyranoside]-5- O -β-glucopyranoside (negretein). The total anthocyanins in the whole ripe fruit was 1.2 mg/g dry weight (DW); 7.1 mg/100 g fresh weight (FW). Chlorogenic acid (the most abundant phenolic acid) was 0.6 mg/g DW; 3.7 mg/100 g FW. The main flavonol, rutin was 0.8 mg/g DW; 5 mg/100 g FW. The total carotenoid content was 211.3 μg/g DW; 1,268 μg/100 g FW. The total phenolic content was 8.6 mg/g DW; 52.2 mg/100 g FW. The vitamin C content was 37.3 mg/100 g FW. The antioxidant activities as measured by the TEAC and ORAC assays were 31.6 and 140.3 μmol TE/g DW, respectively (193 and 855.8 μmol TE/100 g FW, respectively). The results show the unique features of this new tomato genotype with nutraceutical properties.

Grown to Be Blue—Antioxidant Properties and Health Effects of Colored Vegetables. Part II: Leafy, Fruit, and Other Vegetables

“…Interestingly, the oxygen radical absorption capacity assay (ORAC) value for the hydrophilic extracts in purple tomato reported by Li et al [136] was 323.23 µmol trolox/g dw, which was 2-fold higher than the ORAC value of the traditional tomato cultivar San Marzano (140 µmol trolox/g dw) reported by Ninfali et al [148]. Similar observations were made by Blando et al [130] who stated 3-fold higher trolox equivalent antioxidant capacity (TEAC) value (31.6 µmol trolox/g dw) in sun black tomatoes compared with the wild type (10.3 µmol trolox/g dw) at the red-ripening stage. Moreover, antioxidant capacity of purple fruit was higher at the ripe (red ripe stage-RR) fruit compared to the unripe (mature green stage-MG) ones, probably explained by the great increase in polyphenols accumulation during ripening (from 5.8 to 8.6 mg GAE/g dw, in MG and RR, respectively) [130].…”

“…Raiola et al [124] reported the nutritional importance of tomato phytochemicals against inflammation processes and prevention of chronic non-communicable diseases (e.g., obesity, diabetes, coronary heart disease, and hypertension). Anthocyanins normally are not produced in tomato fruit, however, some wild tomato species, such as S. chilense, S. cheesmaniae, S. lycopersicoides, and S. habrochaites biosynthesize anthocyanins in the sub-epidermal tissue of the fruit, and some alleles from those genotypes have been introgressed into cultivated genotypes [130]. Therefore, combining the dominant Anthocyanin fruit (Aft) gene from S. chilense and the recessive atroviolacea (atv) gene from S. cheesmaniae into a cultivated tomato background, anthocyanins biosynthesis has been achieved [131,132].…”

“…Interestingly, during the last 20 years there has been an increasing interest in developing highly consumed food, such as flavonoids-rich tomato fruit. To that direction, transgenic approaches have been applied to modify the biosynthesis of phenylpropanoids, in order to alter the tomato flavonoid biosynthesis [130].…”

“…Phenolic content is varied at different developmental stages of tomatoes, as sun black (SB) tomato had 5.8 and 8.6 mg GAE/g dw phenolic content at mature green and red ripening stage, respectively, contents that were 152% and 134% higher than wild type (WT) [130]. Li et al [136] reported similar total phenolic content (659.11 mg GAE/100 g dw) for purple tomato as has been reported for other tomato varieties (from 290 to 500 mg GAE/100 g dw) [137].…”

“…Apart from chlorogenic acid, naringenin, and rutin Li et al [136] reported other phenolic compounds in purple tomatoes such as p-coumaric acid (15.68±0.74 mg/100 g dw), gentistic acid (15.25 ± 0.76 mg/100 g dw), ferulic acid (14.51 ± 0.99 mg/100 g dw), caffeic acid (13.65 ± 0.83 mg/100 g dw), and protocatechuic acid (8.95 ± 0.16 mg/100 g dw). Indeed, chlorogenic acid content depends on the developmental stage of fruit and varied from 0.5 to 1.3 mg/g dw in sun black (SB) tomato extracts [130]. Moreover, composition of flesh and peel in tomato mutants differed as flesh contained chlorogenic acid (7.96 ± 0.75 mg/100 g fw), quercetin (5.03 ± 1.02 mg/100 g fw), luteolin (0.45 ± 0.01 mg/100 g fw), and total phenolics (1.18 ± 0.06 mg/g fw), while in peel the respective compounds content was: chlorogenic acid (8.43 ± 0.15 mg/100 g fw), quercetin (5276.15 ± 15.10 mg/100 g fw), luteolin (21.28 ± 1.07 mg/100 g fw), and total phenolics (5.95 ± 0.27 mg/g fw) [133].…”