Comparative analysis of polyphenols and flavonoids composition and their scavenging capacity for DPPH radicals in organic tea

Abstract Polyphenols and flavonoids are abundant in herbal teas and are necessary in antioxidant defense. Although the black and green teas are well researched, there is little information on herbal teas. This paper examined the polyphenol and flavonoid composition of 20 organic herbal teas and their roles in antioxidant activity, in terms of DPPH radical inhibition. The Folin-Ciocalteu colorimetry and the aluminum nitrate colorimetry were used to measure total phenolics and flavonoids, whereas the DPPH, ABTS, and hydroxyl radical scavenging assays were used to measure antioxidant activity. There were strong correlations between antioxidant activity and phenolic content (DPPH: r = 0.876; ABTS: r = 0.928; hydroxyl: r = 0.905), with the highest activity observed in dandelion, kuding, mint, peony, and lotus leaf teas. The structure-activity relationships of flavonoid were investigated by means of Cu 2 + chelation, UV-visible spectroscopy, and DNA binding. The copper-flavonoid complexes exhibited redshifts of the UV and improved DNA binding (without strand breaks) suggesting structural changes that lead to bioactivity. Finally, polyphenols are the main source of antioxidant activity of herbal teas, and flavonoids contribute to the effects through metal binding and interaction with DNA. These findings justify the creation of effective herbal teas in the management of oxidative stress.