TLC-DPPH separation and determination of radical
scavenging activity
Crude extract of G. changi was subjected to thin layer
chromatography study. The solvent system optimized for G.
changii crude extract was methanol and: Chloroform (85:15
v/v). The plates were developed in an unsaturated chamber to
the distance of 75 mm. After 15 min air-drying, the plates were
sprayed by 0.04% DPPH solution for 5 seconds and images were
observed under visible light at exactly 2 min after spraying. The
area of bright yellow bands against the purple background then
determined radical scavenging activity.
Total phenolic compound analysis
The amount of total phenolics in G. changii extracts was
determined with the Folin-Ciocalteu reagent using the method
of Spanos and Wrolstad [10], as modified by Lister and Wilson
[11]. To 50 ml of each sample (three replicates), 2.5 ml 1/10
dilution of Folin-Ciocalteau’s reagent and 2 ml of Na2CO3
(7.5%, w/v) were added and incubated at 45 o
C for 15 min.
The absorbance of all samples was measured at 765 nm
using a UV–vis spectrophotometer (GAT UV-9100). Results
were expressed as milligrammes of gallic acid (20-50µg/ml;
R2
=0.963) equivalent per gram of dry weight (mg GAE/g dw)