Variation for antioxidant activity and antioxidants in tomato

Tomato (Lycopersicon esculentum Mill.) is among the most widely consumed vegetables worldwide and an important source of certain antioxidants (AO) including lycopene, beta-carotene, and vitamin C. Improvement of tomato for content of AO and overall antioxidant activity (AOA) could potentially benefit human health in many countries. We evaluated 50 L. esculentum and three L. pimpinellifolium (L.) Mill. entries for contents of lycopene, beta-carotene, ascorbic acid, total phenolics, and two assays for antioxidant activity [anti-radical power (ARP) and inhibition of lipid peroxidation (ILP)] for 2 years during the same period in south Taiwan. We detected high levels of genetic diversity for the AO and AOA measured in this study. Group means of the L. pimpinellifolium entries were significantly higher than L. esculentum group means for ARP, ILP, lycopene, ascorbic acid, phenolics, and soluble solids concentration, suggesting that introgression of alleles from L. pimpinellifolium may have potential to improve cultivated tomato for these traits. Ranking of entries for ILP and ARP were consistent between years, particularly for those entries with the highest means and these assays could be adopted by tomato breeders. Results from ILP and ARP assays were highly correlated (r=0.82**) and it would be unnecessary to use both assays for tomato. Lycopene, beta-carotene, ascorbic acid, soluble solids, and total phenolics were all positively correlated with ARP. Among AO, total phenolics content was most closely associated with ARP (r=0.90**) and ILP (r=0.83**); this suggests that phenolics make a major contribution to AOA in tomato fruit. Fruit size was negatively correlated with ARP (r=-0.74**) and ILP (r=-0.71**), indicating that combining large fruit size and high AOA will be challenging.