Polyphenol content and antioxidant capacity in organically and conventionally grown vegetables

Abstract

Objective: To evaluate the polyphenol content and antioxidant capacity of ethanol extracts of some organically and conventionally grown leafy vegetables. Methods: The ethanol extracts of kailan (Brassica alboglabra), bayam (Amaranthus spp.) and sawi (Brassica parachinensis) were tested for total phenolic content (TPC), total flavonoid content (TFC), and total anthocyanin content (TAC) and the antioxidant capacity of the extracts measured using 2,2-diphenyl-1-picrylhydrazyl assay. Results: In TPC test, sawi extract showed the highest phenolic content while bayam contained the least phenolic content for both organically and conventionally grown types. In TFC test, organically grown sawi extract showed the highest flavonoid content, while organically grown kailan extract showed the least flavonoid content among all types of vegetables. The flavonoid content of the conventionally grown types of vegetable extracts was the highest in kalian and the least in sawi. For 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, the activity increased with the increasing concentration of each extract. All conventionally grown vegetable extracts showed higher antioxidant activity compared to their organically grown counterparts. Extracts of conventionally grown sawi showed the highest percentage inhibition followed by conventionally grown kailan and organically grown sawi. There were no correlation between TPC, TFC, TAC and IC25 of both organically and conventionally grown vegetables. However, there was a correlation between TAC and IC25 of conventionally grown vegetable extracts. The results showed relatively similar polyphenol content between organically and conventionally grown vegetable extracts. However, the conventionally grown vegetables extracts generally have higher antioxidant activity compared to the organically grown extracts. Conclusions: These results suggested that the different types of agricultural practice had a significant contribution to the polyphenol content and antioxidant activity in the vegetables.