Investigation of phenolic compounds in several vegetables in Vietnam and their antioxidant capacities

Abstract

The total phenolic content, flavonoid, β-carotene and their antioxidant capacity in several vegetables (Carrot, taro, tomato, beetroot and eggplant) in Vietnam was investigated in this study. Using two different drying methods in samples preparation was to examine the effect of drying process on total phenolic content and antioxidant activity. The total phenolic content was measured by Folin-Ciocalteu method, expressed as µg GAE/g db sample and antioxidant capacity was determined by 2-2- diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging. Phenolics were mainly located in free form which easily extract by alkaline methods. The high temperature in conventional drying method in sample preparation was effect on total phenolic content, flavonoid and their antioxidant capacity. The concentration of free phenolic was highly correlated with antioxidant activity (r2=0.893) and correlation between free flavonoid and antioxidant properties was moderately high (r2=0.668). Bound phenolics and flavonoid was not correlated with antioxidant capacity (r2=0.003 and r2=0.078, respectively). Although, β-carotene possessed antioxidant properties, there was weakly correlation (r2=0.495) between antioxidant capacity and β-carotene.

Key words: Total phenolic content, Flavonoid, β-carotene, antioxidant capacity