Conclusions
This study clearly indicated that P. foetida and S. aqueum, both have high antioxidant activity.
Fresh samples had higher phenolic contents and better antioxidant activity than did dried samples.
There is not much difference in the total phenolic content between the leaves and twig of P. foetida. A
good correlation between the β-carotene oxidation and ABTS methods was observed, with an R2 =
0.9878. The present study confirms that P. foetida and S. aqueum could be significant sources of
natural antioxidant compounds that may have potent beneficial health effects.
Experimental
Preparation of samples
Plant materials were collected from trees growing in home gardens in Gelugor, Penang, Malaysia.
Upon arrival at the laboratory, samples were washed with water to remove debris. The leaves and
twigs of P. foetida and leaves of S. aqueum were stripped from the plants. Plant materials (500 g) were
divided into fresh and dried samples. The dried samples were air dried at room temperature (30 °C) for
14 days until a constant weight was achieved. Fresh samples were air dried at room temperature (30
°C) for 24 hr and were immediately immersed in the solvents used for extraction.
Preparation of extracts
All fresh and dried samples were extracted with methanol: water (1:10). The aqueous methanol
solution was then filtered through Whatman No. 4 filter paper and the solvent was removed in vacuo.
The crude extract was transferred into a 100 mL volumetric flask and ethanol was added up to the
mark to prepare solutions at different concentrations (0.005 - 0.1 mg mL-1). The extracts were stored at
-20 ºC. These crude leave extracts of P. foetida and of S. aqueum were subjected to ABTS free