Synergistic effect of herbal plant extract (Hibiscus sabdariffa) in maintain the antioxidant activity of decaffeinated green tea from various parts of Assam.

In the present study, two extraction methods, hot water extraction and ethyl acetate extraction were used to decaffeinate fresh green tea leaf (Camellia assamica) collected from four parts of Assam, NE-India. Both type of extraction methods have significant effect on the antioxidant activity of decaffeinated green tea. Amongst the four samples, Dhekiajuli sample have highest antioxidant activity and total polyphenol as well as flavonoid contents. During hot water extraction (100 °C for 3 min), in decaffeinated green tea, the antioxidant activity decreases to 996.1 ± 26.12 mM TE/g green tea and 1165 ± 31.25 mM TE/g green tea from 1403.07 ± 70.15 mM TE/g and 1587.1 ± 79.355 mM TE/g green tea as observed for caffeinated green tea by DPPH and FRAP assay respectively. Again more antioxidant activity (ranges from 996.1 ± 15.8 to 1421.3 ± 71.06 mM TE/g) was recorded for ethyl acetate extracts compared to hot water extracts of samples. However, the loss in antioxidant activity, due to decaffeination of green tea in our study was minimize by using herbal plant extract, Hibiscus sabdariffa along with the tea extract which shows a synergistic effect. © Association of Food Scientists & Technologists (India) 2019.