P. edulis is an indigenous plant which has been cultivated for its edible tuber. It is claimed to have antibacterial activity. But this was not supported by scientific investigation. Hence this work explores the antibacterial and antioxidant activities of extracts and isolated compounds from the tuber of P. edulis. The effects of the extracts and isolated compounds of tubers of P. edulis were evaluated against S. aureus, E. coli, P. mirabilis and K. pneumonia using disc diffusion method. The antioxidant activities were evaluated using DPPH and ferricthiocyanate methods. Silica gel column chromatography and spectroscopic methods were employed for isolation and characterization of compounds, respectively. The tuber extracts after silica gel column chromatography furnished methyl linoleate, α-spinasterol (1) and 3,5,7-trihydroxy-6,4’-dimethoxyflavone (2) with the latter two compounds new to the genus. The ethyl acetate extract displayed inhibition zone of 11 mm at 100 mg/mL against E. coli which is significant compared with positive and negative controls. 3,5,7-trihydroxy-6,4’-dimethoxyflavone exhibited 12 and 14 mm zone of inhibition against S. aureus and E. coli, respectively. The MeOH and EtOAc extracts inhibit DPPH radical by 84 and 76%, respectively. While their anti-lipid peroxidation activity was found to be 78 and 75%, respectively. α-Spinasterol (1) and flavone (2) displayed pronounceable antibacterial activity compared with the standard drug, indicating that the tuber of P. edulis could be a good source for the antibacterial to combat diseases caused by bacteria. The tuber extracts and flavone (2) exhibited strong antioxidant activity indicating the potential of P. edulis as a natural antioxidant.
Keywords: Antibacterial, Antioxidant, 3,5,7-trihydroxy-6,4’-dimethoxyflavone