Isolation of potential antimicrobial metabolites from endophytic fungus Cladosporium cladosporioides from endemic plant Zygophyllum mandavillei

Abstract

This study aimed to test and evaluate antibacterial and antifungal activities of secondary metabolites obtained from endophytic fungi isolated from the leaves of endemic plant Zygophyllum mandavillei. The fungus Cladosporium cladosporioides was the predominant isolated fungus with colonization and dominance frequencies percentage of 12.50 and 39.32 respectively. C. cladosporioides extract was found to have the best antimicrobial activity causing a zone of inhibition ranging from 20.7 to 25.7 mm against all tested bacterial and fungal phytopathogens. Gas Chromatography/Mass Spectrometry (GC/MS) analysis of the extract successfully identified six major compounds: Cladosporin, Isocladosporin, 5′- hydroxyasperentin, Di (2-ethylhexyl) phthalate, 1-acetyl-17-methoxyaspidospermidin-20-ol, and 3-phenylpropionic acid. Enhanced antimicrobial activity was recorded for 3-phenylpropionic acid with MIC value ranging from 3.90 to 15.62 μg/ml followed by 5′- hydroxyasperentin with MIC ranging from 7.81 to 62.5 μg/ml. The most effective compound, 3-phenylpropionic acid, was further characterized by Fourier transform infrared spectroscopy (FT-IR) in addition to nuclear magnetic resonance (NMR) and mass spectroscopy to elucidate the chemical structure. The cytotoxicity of 3-phenylpropionic acid revealed a lower level of cytotoxicity at the concentration range 0.01–10 µg/ml as indicated by the cell viability percentage which is ranging from 75.47–94.14%. These results suggested that 3-phenylpropionic acid may serve as a potential alternative approach for the management of plant phytopathogens.