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Phenol content and antioxidant activity of green, yellow and black tea leaves

Green, black and yellow tea leaves are rich in phenolic compounds that are known for their antioxidant activity thus beneficial effect on human health. In practice, different methods are used to determine antioxidant activity. The objective of this study was to determine content of phenols, flavonoids and tannins, as well as antioxidant activity of tea leaves. Green, yellow and black tea leaves (leaves and powdered leaves) were used for extraction by methanol or acidified methanol. Spectrophotometric methods were used for determination of selected parameters. Antioxidant activity was determined in extracts and powdered tea leaves by application of 2, 2-diphenyl-1-picrilhydrazyl (DPPH) and 2, 2’azinobis-(3-ethylbenzthiazoline-6-sulphonicacid (ABTS) free radicals. “QUENCHER” method for determination of antioxidant activity is based on direct treatment of dry sample with free radicals (DPPH and ABTS). Extracts obtained by extraction of powdered tea leaves with acidified methanol had the highest phenol content (3.823, 4.226 and 6.829 g/kg for green, black and yellow tea). In methanol extracts phenol content decreased in order yellow > green > black tea, and in acidified methanol extracts yellow > black > green tea, regardless of particle size. Flavonoid and tannin contents followed the same tendency as phenol content. The highest antioxidant activity had acidified methanol extracts of powdered tea leaves, regardless of used method (DPPH and ABTS). Results of antioxidant activity obtained with “QUENCHER” method were compared with results of acidified methanol extracts. Green and yellow tea had higher antioxidant activity when „QUENCHER“ method was used in contrast to black tea where higher antioxidant activity was determined in extract. Particle size and extraction solvent had high influence on investigated parameters. Extracts obtained by extraction of powdered tea leaves with acidified methanol had the highest phenol content and antioxidant activity.

Green; yellow and black tea leaves; Phenol content; Antioxidant activity; DPPH; ABTS; QUENCHER method.

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