All these properties are involved in the overall anti-oxidant
activity, which makes it suitable for the prevention of human
disease in which free radicals play an important role [13-14].
Dose inhibition curve and IC50 values of the crude extract
are shown in Fig 2. In the dose-response experiment it could
be observed that total inhibition of the enzymes was never
achieved. Maximal inhibition was in the range of 75-85%,
in the presence of 25 mg/ml extract. With the addition of
larger amount of extract to DPPH assay mixture, the degree
of inhibition decreased, indicating a pro-oxidant effect. The
explanation for the higher IC50 (IC50 = 14.70 mg/ml) value
found in the experiment was because the sample used was a
crude extract with the compound(s) react as antioxidant.
Result of the TLC-DPPH separation and determination of
radical scavenging activity showed in Figure 3. Our thin layer
chromatography study showed that the crude extract of G.
changii contained 7 major bands. A major part of compounds
in G. changii crude extract was found to be inactive based on
DPPH scavenging area. Only one DPPH radical scavenging
band was separated and detected with Rf
value 0.63 (Figure. 3).
In such situation, the real concentration for the compound(s),
which reacts as an antioxidant, was very low in the crude
extract.
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