Study of the biological activities of Physarum polycephalum and Physarella oblonga plasmodial extracts

Various species of myxomycetes have been found to produce bioactive compounds that appear to considerable potential for pharmaceutical applications. However, obtaining a sufficient amount of sample material for studying the bioactive compounds of myxomycetes has been a real challenge due to the small size of their fruiting bodies in the field and the slow growth rates of their plasmodia on synthetic media under laboratory conditions. The research reported herein was carried out first to study the effects of carbon source and carbon concentration on the growth of Physarum polycephalum and Physarella oblonga and then to evaluate antimicrobial and anticancer activities of their plasmodial extracts. Physarella oblonga was found to grow better on agar without nutrients, as it has ability to hydrolyze agar as a carbon source. The best agar concentration for the growth of this species was 19g/L, and at this concentration a remarkably high amount of plasmodia (92.05 g/L) was obtained. In contrast, Physarum polycephalum preferred glucose as a carbon source, and 20g/L of glucose was found to be the most suitable amount for this species. At this gulcose concentration, 65.02 g/L of plasmodia was produced. In term of antimicrobial activity, none of the Phy. oblonga extracts showed inhibitory activity on the pathogens tested. However, 90% MeOH and 90% MeOH: 90% acetone extracts of Ph. polycephalum showed antimicrobial activity toward Staphylococcus aureus. Data on the minimum inhibitory concentration (MIC) showed that S. aureus was more susceptible to the extract of Ph. polycephalum 90% MeOH: 90% acetone as the MIC of this extract was in the range of 1.56 to 0.78 mg/mL, whereas that of the 90% MeOH extract was between 6.25 and 3.12 mg/mL. However, the minimum bactericidal concentration values of these two extracts were found to be the same (at 12.5mg/mL). Initially, studies of the cytotoxicity of the extracts found that Phy. oblonga extracts could inhibit the tested cancer cell lines better when compared to those of Ph. polycephalum. Notably, MeOH: Chl Phy. oblonga had an inhibitory rate of 31.95 +/- 6.37% on Jurkat blood cancer cells.