Antioxidant activity of Phyllanthus watsoni extract and its major isolated constituents

Phyllanthus watsoniiis one of Malaysia’s traditional medicinal herbs and is endemic to the Endau-Rompin area. Although several studies on the bioactivity and phytochemistry of P. watsoniihave been reported, information on its antioxidant potential and major chemical constituents remains limited. Therefore, this study aimed to evaluate the in vitroanti oxidant activity of the crude extract and its major isolated constituents. The antioxidant activity was assessed using the ferric thiocyanate (FTC) method, thiobarbituricacid (TBA) method and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay. Isolation and purification of the major constituents were carried out using open column chromatography. The purified constituents were further identified and elucidated using spectroscopic techniques, including nuclear magnetic resonance (NMR), gas chromatography–mass spectrometry (GC-MS) and Fourier-transform infrared spectroscopy (FTIR).The crude extract of P. watsoniishowed more than 90% inhibition in all three antioxidant assays. Among the isolated constituents, glochidonol (PW2) exhibited more than 90% inhibition in the FTC and TBA assays. Based on these findings, P. watsonii possesses strong antioxidant activity, with glochidonol (PW2) identified as one of the major contributors to this activity. These results suggest that P. watsoniiis a promising source of natural antioxidants and has potential for further development in food and nutraceutical applications.