Chiang Mai Journal of Science

Aqueous extract of Stephania pierrei tubers was studied for phytochemical screening and antibacterial activities as well as for cepharanthine concentration. The results revealed that the presence of alkaloids, triterpenoids, tannins, polyphenols, phenolic compounds of 41.49±0.66 mg GAE/g extract and cepharanthine content of 33.68 mg/g extract was found in the extract. The extract exhibited dose dependent microbial activities, moreover, the antibacterial activities were observed against Gram-positive bacteria (Staphylococcus epidermidis and Staphylococcus aureus) using disc diffusion assay. Especially, S. epidermidis was more sensitive to the extract than S. aureus. S. epidermidis was susceptible to the extract with the MIC and MBC of 2 and 6 mg, respectively. The ultrastructure alteration in extract-treated S. epidermidis cells was studied using transmission electron microscopy (TEM). The bacterial cell wall was ruptured after treated with the extract for 24 h. The characterization of functional groups was achieved by Fourier transform infrared spectroscopy (FTIR). FTIR spectra revealed changes in spectral regions corresponding to changes in fatty acid and polysaccharide on cell wall.