Study on Antioxidant potency of Green Tea by DPPH Method.

The present study was conducted to compare antioxidant activity of green teas, fermented teas and other related common teas by examining radical scavenging activity using DPPH (2,2 Diphenyl 1‐picryl hydrazyl). Scavenging activity (SC50) of epigallocatechin gallate (EGCG) for 0.1 mM DPPH radical was 5.5 uM or 4.2 mg/L by weight, then catechin, 14 uM or 2.5 mg/L and vitamin C, 22 uM or 3.9 mg/L, respectively. Kyokuro tea (okro) powder of 24.2 mg/L or green tea powder of 25.2 mg/L was used to reach SC50 for 0.1 mM DPPH. One serving of 2g green tea provides antioxidant activity equivalent to 109–147 §· EGCG, 145–185 §· catechin or 131–168 §· vitamin C. Teas from the first harvest had the highest radical scavenging activity when compared with later harvest green teas grown in the same region, but there is virtually no difference by the harvest time. A Chinese green tea, Dragon well had the highest antioxidant activity among other green teas tested providing antioxidant capacity equivalent to 168 §· EGCG or 188 §· vitamin C per 2 g serving, but partially fermented Chinese teas had much lower antioxidant activity than any green tea tested. Black tea which is fully fermented showed as strong antioxidant activity as green teas (76.3 §· vs 86.7–67.6 §· per tea bag). One tea bag of green teas from market provided antioxidant capacity equivalent to 52–86 §· EGCG, 70–105 §· catechin or 63–96 §· vitamin C. Teas made of persimmon leaf, pine needle, mulberry leaf had comparatively low antioxidant activity equivalent to 2.5–4.8 §· EGCG or 15–21 §· vitamin C per teabag. Partially fermented Chinese teas were low in antioxidant activity while fully fermented black tea had strong antioxidant activity. More systemic studies are needed to clarify the relationship between tea fermentation and catechin concentrations.