Antioxidant Activity, Total Phenolics and Isoflavones in Vegetables Available in Thailand

ABSTRACT

Introduction: Increased interest in phenolic compounds is largely due to findings of their association with antioxidant, antimutagenic, antibacterial, anticarcinogenic, and anti-inflammatory activities with reduced risk of free radicals related diseases. Local vegetables of Thailand were examined for antioxidant activity, total phenolics and isoflavone contents. Methods: Thirty edible leaf and 13 other-parts of vegetable plants were collected from the markets in Northern Thailand for analysis of antioxidant activity (DPPH and ABTS assays), total phenolics, and isoflavones. Results: The antioxidant activity for DPPH assay and total phenolics of edible leaf vegetables (EC50 = 541.2+498.9 jug/ mL and 2438.7+3342.7 pg GAE/g dry extract respectively) were significantly higher than those of the other edible plant parts (EC50 =1315.5±1303.4 pg/mL and 1263.3+3281.7 pg GAE/ g dry extract respectively). Ten types of edible leaf vegetables and only one example of plant part, namely ginger, exhibited high antioxidant activity. The antioxidant activities for DPPH and ABTS assays were associated with total phenolics concentration. Conclusion: Antioxidant activity and total phenolics of Thai edible leaf vegetables were higher than those of other edible plant parts. The Thai copper pod showed the highest levels of total phenolics and isoflavones, and strong antioxidant activity. Further investigation should be undertaken to examine the active mechanisms of these properties in relations to health benefits.