Helvolic acid, an antibacterial nortriterpenoid from a fungal endophyte, Xylaria sp. of orchid Anoectochilus setaceus endemic to Sri Lanka

Pamoda B Ratnaweera; David E Williams; E Dilip de Silva; Ravi L C Wijesundera; Doralyn S Dalisay; Raymond J Andersen

doi:10.1080/21501203.2014.892905

Helvolic acid, an antibacterial nortriterpenoid from a fungal endophyte, Xylaria sp. of orchid Anoectochilus setaceus endemic to Sri Lanka

Mycology. 2014 Mar;5(1):23-28. doi: 10.1080/21501203.2014.892905. Epub 2014 Mar 25.

Authors

Pamoda B Ratnaweera¹, David E Williams², E Dilip de Silva³, Ravi L C Wijesundera⁴, Doralyn S Dalisay², Raymond J Andersen²

Affiliations

¹ Department of Chemistry, University of Colombo, Colombo 03, Sri Lanka ; Department of Science and Technology, Uva Wellassa University, Badulla, Sri Lanka.
² Department of Chemistry and Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada.
³ Department of Chemistry, University of Colombo, Colombo 03, Sri Lanka.
⁴ Department of Plant Sciences, University of Colombo, Colombo 03, Sri Lanka.

Abstract

An endophytic fungus was isolated from surface sterilized leaf segments of Anoectochilus setaceus, an orchid endemic to Sri Lanka, and was identified as Xylaria sp. by morphological characters and DNA sequencing. Bioassay-guided chromatographic fractionation of the organic extract of a laboratory culture of this fungus led to the isolation of the known antibacterial helvolic acid. Helvolic acid was active against the Gram-positive bacteria, Bacillus subtilis [minimal inhibitory concentrations (MIC), 2 μg mL^-1] and methicillin-resistant Staphylococcus aureus (MIC, 4 μg mL^-1).

Keywords: Anoectochilus setaceus; Xylaria; antibacterial; endophytic fungi; helvolic acid; rainforest.