Antifungal Activity of Compounds Isolated from Bamboo Vermicompost against &i&Rhizoctonia solani&/i& AG1-IB

摘要

Vermicompost has become a promising alternative to chemical pesticide because of its disease suppression effect during these decades. However, the mechanisms by which vermicompost suppress plant disease are not well-understood. Antifungal compounds, which are released by beneficial organisms in the vermicompost, may play an important role in inhibiting plant pathogens; however, these mechanisms have not been widely examined. In this study, Sterilized Water Extracts of bamboo vermicompost (SWE), using a 0.22-μm cellulose acetate filter, significantly (P < 0.05) inhibited the mycelium growth of Rhizoctonia solani AG1-IB on a Potato Dextrose Agar (PDA) plate. This suggests that antifungal compounds are present in bamboo vermicompost. The ethanol acetate (EtOAc) crude extracts of bamboo vermicompost showing antifungal activity were further separated. Two compounds were isolated from the EtOAc fraction of bamboo vermicompost and characterized as ergosterol peroxide (1 ) and (22E , 24R )-5α ,8α -epidioxyergosta-6,9(11),22-trien-3β -ol (2 ). Their chemical structures and mass spectra were determined by nuclear magnetic resonance and mass spectrometry analyses. Ergosterol peroxide tested at 150, 300, 600, and 900 μg showed 13%, 22%, 34%, and 53% mycelial growth inhibition against R . solani AG1-IB, respectively. Because EtOAc crude extracts of the initial substrate materials of bamboo vermicompost did not inhibit mycelium growth of R . solani AG1-IB, antifungal compounds in the vermicompost may be released by microbes but not from the original substrates during vermicomposting.