Abstract:
The significance of Afgekia mahidolae Burtt et Chermsir. as the symbol of Mahidol University and lack of phytochemical and biological studies led to the attempt to isolate the biologically active components. The study was carried out to isolate and identify the antioxidant compounds based on bioassay-guided fractionation. Leaves, petioles, flowers and peduncles of Afgekia mahidolae were extracted with methanol by maceration to yield 1.46, 1.18, 1.11 and 1.45 g of dried extracts, respectively. All the extracts were tested for free radical scavenging activity with 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and antibacterial activity against common pathogenic strains by disc diffusion and broth dilution methods. The leaf extract of A. mahidolae showed the strongest free radical scavenging activity (EC50 22.07 mg/ml) and only peduncles of A. mahidolae exhibited weak antibacterial activity against Staphylococcus aureus (ATCC 25923) (inhibition zone 1.00 cm and MIC > 2.5 mg/ml). The leaves of A. mahidolae were selected for further studies. The leaves were successively extracted with petroleum ether, chlorofrom, ethyl acetate and methanol to yield 24.76, 9.24, 6.85 and 80.92 g of extracts, respectively. The petroleum ether extract exhibited strongest free radical scavenging activity, therefore, this extract was separated by repeat column chromatography and compounds A, B, C and D were obtained. Their structures were elucidated on the basis of spectral data including 1D and 2D NMR, IR and MS as n-pentacosane, 1-triacontanol, butyl dotriacontanoate and n-octatriacontanal, respectively. However, only n-octatriaconta-nal exhibited free radical scavenging activity