Antimicrobial, cytotoxic and phytotoxic potency of ethyl acetate extract of Rhizopus stolonifer culture

Purpose: To evaluate the antimicrobial, cytotoxic and phytotoxic activities of the organic extract of Rhizopus stolonifer whole cell static culture in order to determine the presence of potentially bioactive compounds in the culture. Methods: The organic extract was obtained by extracting the whole cell culture of R. stolonifer with Ethyl Acetate (EtOAc). The antifungal activity was determined by inhibitory effect on the growth of Alternaria alternate, Aspergillus flavus, Curvularia protuberata and Fusarium oxysporum, cytotoxic activity by brine shrimp lethality test, antibacterial activity against Ervinia carotovora and Xanthomonas campestris by disc diffusion technique, and phytotoxic activity by testing the crude extract against the Lemna minor frond. Results: The extract showed phytotoxic activity (at 95% level of significance) against Lemna minor (67.7 % lethality) with Fronds Inhibition (FI₅₀) of 167.85 μg mL^-1. The extract exhibited a significant (at 95% level of significance) cytotoxic activity (LC₅₀ of 115.71 μg mL^-1) against brine shrimp. Maximum mortality (56.7 %) was obtained at a concentration of 200 μg mL^-1 concentration after 48 h. In the antifungal test, the highest inhibitory effect was observed against Fusarium oxysporum (88.8 %) followed by Alternaria alternata (81.5 %), Aspergillus flavus (70.5 %) and Curvularia protuberata (37.5 %) at 1000 μg. mL^-1 when compared to negative reference. Antibacterial activity against Ervinia carotovora and Xanthomonas campestris was minimal even at extract level of 2000 μg mL^-1. Conclusion: The ethyl acetate extract of R. stolonifer possesses significant herbicidal, cytotoxic and antifungal properties. Isolation and characterization is required for structural elucidation of its bioactive compounds.