Variation in Antioxidant Activity and Polyphenol Content in Tomato Stems and Leaves

Tomato was considered as one of the most widely cultivated vegetable crops in the world. Tomato plant has high antioxidant capacity which can be attributed to the high levels of carotenoids, phenols, vitamins C and E. However, most of tomato plants have been discarded as waste after fruit harvesting. In order to identify genetic resources with high antioxidant level for use in food or as feed additives, we investigated the ABTS, DPPH antioxidant activity and polyphenol content in tomato leaves and stems. A total of 112 tomato accessions were classified into three groups by latitude of their collected countries: 30°~60° North (50 accessions), 0°~30° North (40 accessions), and 0°~30° South (22 accessions). Stem and leaf extracts showed wide variation in ABTS antioxidant activity ranging from 1.6 ± 1.0 to 48.4 ± 6.1 μg Trolox mg -1 dw. The antioxidant activity of DPPH was in the range of 6.3 ± 0.2 to 40.0 ± 0.3 μg ASC mg -1 dw. Total polyphenol content ranged from 6.1 ± 0.2 to 38.9 ± 0.7 μg GAE mg -1 dw. ABTS, DPPH antioxidant activities and polyphenol content in accessions from 30°~60°N latitude were significantly higher (P<0.05) than those from 0°~30°N latitude. ABTS values showed a significant positive correlation (r = 0.700**) with DPPH activity. IT100506 (KOR) and 702959 (UKR) were recommended as potential sources of natural antioxidants due to their highest antioxidant activity among accessions. This study will provide valuable information for tomato breeders in developing and producing functional food or feed additives resources.