ANTIOXIDANT ACTIVITY OF <em>THUNBERGIA</em> <em>LAURIFOLIA</em> TEA

Abstract

CHAN, E. W. C. & LIM, Y. Y. 2006. Antioxidant activity of Thunbergia laurifolia tea. Different drying
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.