Abstract

The antioxidant activity of water extracts (cold and hot) of six caffeine products were carried out. The extracts were screened for total polyphenol contents and antioxidant activity using DPPH, ABTS methods and reducing power method at 50 and 100 µg/ml after 15 and 30 min using BHA and Caffeine as standard compounds. The results indicated that, the hot water extracts for different caffeine products showed high antioxidant activity more than cold extracts and this activity was time and concentration dependent. In addition, the activity was higher against ABTS radical more than DPPH and reducing power methods. Also, there is positive correlation between the antioxidant and reducing compounds presented in water extracts of different caffeine products. The results of HPLC showed that fresh tea leaves are rich in flavanol monomers known as catechins. The most abundant catechin derivatives in green tea are EGC, EGCG and GC. On the other hand, EGCG and GC are major catechin derivative in different caffeine product except El-Fakher tea and Cacao. Generally, these beverages had high antioxidant capacities and total phenolic contents and could be important dietary sources of antioxidant phenolic for prevention of diseases caused by oxidative stress.

Key words: Caffeine product, antioxidant activity, phenolic contents.