Quantification of polyphenols and antioxidant activity in several herbal and green tea products in Malaysia

Abstract

Herbal tea and green tea are widely consumed around the world as it is believed to have beneficial health effects and contained high amount of antioxidant. Malaysia is rich with various herbal resources which can be transformed into tea. However, there is limited reports available on the antioxidant properties of herbal tea products from Malaysia. Therefore, the polyphenols and antioxidant activity of three green tea and herbal tea products were investigated in this study. The polyphenols content of the tea products were determined by total phenolic content (TPC) and total flavonoid content (TFC). Whilst, the antioxidant activity of the tea samples were determined by ferric reducing antioxidant power (FRAP) assay and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) assay. The effects of water volume and steeping period on the antioxidant properties of tea infusion were investigated. Subsequently, the effect of tea infusion storage at 4°C in comparison to the hot tea infusion were studied. The results indicated that green tea has higher polyphenols content and FRAP values as compared to the herbal tea. Interestingly, the storage of the tea infusion at 4°C for 24 h did not significantly affected the polyphenols content in majority of the tea samples. Moreover, the steeping period did not affect the DPPH scavenging but inversely reduced the FRAP values at longer steeping period. TPC and TFC were positively correlated to the antioxidant activity suggest that phenolic compounds and flavanoids could be two of the components responsible for antioxidant activities of these tea infusion. Tea infusion preparation technique is important to preserve antioxidant potency in order to serve its benefit.