Journal of Tropical Forest Science 18(2): 130–136 (2006)130 ANTIOXIDANT ACTIVITY OF THUNBERGIA LAURIFOLIA TEA

treatments were tested on Thunbergia laurifolia leaves to produce a tea with total phenolic content (TPC) and antioxidant activity (AOA) comparable to fresh leaves and with acceptable aroma. TPC was measured using the Folin-Ciocalteu method while AOA was measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and ferrous ion chelating (FIC) assays. Using a household microwave oven for drying, Thunbergia tea with superior antioxidant activity could be produced. Unlike oven-dried and sun-dried leaves, TPC and AOA of microwave-dried Thunbergia leaves were higher than fresh leaves. Leaves microwave-dried for 4 min remained green with a faint fragrance and when ground, the aromatic green coloured tea produced a mild tasting green infusion. The efficiency of hot water extraction as part of normal tea brewing was assessed, and TPC and AOA of the microwave-dried tea were compared with other commercial teas. The microwave-dried Thunbergia tea is far superior in terms of TPC and AOA compared with all the commercial herbal teas tested (Java, rooibos and rang jeud). Green and black tea of Camellia sinensis, however, showed higher TPC and AOA. Nonetheless, the microwave-dried Thunbergia tea had the best chelating ability among all the commercial teas studied, including those of green and black tea