Effects of infusion conditions on bioactive compounds and antioxidant activities of banaba herbal

Banaba (Lagerstroemia speciosa L.) is normally consumed as an herbal tea by infusing the banaba powder in hot water. However, the infusion method may influence the bioactive compounds, antioxidant activities, and enzyme inhibitor activities of the tea. Therefore, the objective of this study was to determine the effects of the infusion conditions on the bioactive compounds, antioxidant activities, and on the inhibition against α-glucosidase and α-amylase in banaba instant tea. Banaba extract powder (BEP) was produced by water extraction with the ratio of 1:10 and 1:8 (w/w) at 90 oC and was dried using a spray dryer with the addition of 3% gum arabic. Then the effects of the infusion conditions were investigated by varying the water temperatures (80, 90, and 100 oC) and the amount of BEP (2, 4 and 6 g). The investigated parameters were tannin content, total phenolic content (TPC), αglucosidase inhibitor, αamylase inhibitor and antioxidant activities dinitrosalicylic acid 1,1diphenyl2pieryhdrazyl (DPPH) scavenging activity and Ferric Reducing Antioxidant Power (FRAP). The results indicated that tannin content, total phenolic content (TPC), α-glucosidase inhibitor, α-amylase inhibitor, DPPH and FRAP had significantly increased with increased amounts of BEP (p<0.05) . This study also showed that higher water temperature had affected to bioactive compounds and antioxidant activities of the banaba tea (p<0.05) . Infusion at 100 oC showed the most effective condition, providing a high concentration of bioactive compounds, antioxidant activities, and α-glucosidase and α-amylase inhibitor activities.