Estimation of total phenolic contents and antioxidant capacities in some green and black tea of Saudi Arabia markets and evaluation of their antibacterial activity

Abstract

Tea is the most commonly consumed beverage in the world after water and considered a good antioxidant nutrient against free radical reactions. Teas are classified into more than one type depending on the manufacturing process. Green and black tea leaves are rich in phenolic compounds that are known for their antioxidant activity, having a beneficial effect on human health. The objective of this study was to determine phenolic content, antioxidant capacities as well as the antibacterial activity of green and black tea for the most popular brands in Saudi Arabia, Lipton and Rabea. The results showed that the content of polyphenols was higher for green brands 524.10 ± 11.8 and 553.75 ± 14.0 mg/g than black brands 468.70 ± 10.5 and 466.25 ± 6.8 mg/g for Lipton and Rabea types respectively. Moreover, it was found that all tea types exhibited high antioxidant activity, but green tea brands were higher 93.94 and 94.08 % than black brands 93.64 and 93.32 % for Lipton and Rabea brands respectively. Test of antibacterial activity showed that green tea was more effective in inhibiting the growth of the test organisms than black tea, where it showed antibacterial activity with a mean diameter of inhibition zone ranged from 9.0 ± 0.22 to13.0 ± 0.24 mm in comparison with black tea 9.0 ± 0.20 to 11.0 ± 0.10 mm. The present study indicated that no significant differences were noted in total phenolic contents and antioxidant activities for black and green tea. but Rabea green tea exhibited stronger antibacterial activity than black tea brands. To our knowledge, no studies have so far been done to compare these properties of two commercial black and green teas available in the markets of Saudi Arabia.