Helvolic Acid, A Secondary Metabolite Produced by Neosartorya spinosa KKU-1NK1 and Its Biological Activities

Abstract

Helvolic acid, an antimicrobial metabolite was isolated from the crude ethyl acetate extract of the soil fungus [A1] Neosartorya spinosa KKU-1NK1. The isolated helvolic acid inhibited growth of[A2] Gram positive [A3] pathogenic bacteria (Methicillin-resistant Staphylococcus aureus DMST 20654, Staphylococcus aureus ATCC 25923, Staphylococcus saprophyticus ATCC 15305, Streptococcus pneumonia DMST 15319, Enterococus faecalis ATCC 29212 and Bacillus subtilis ATCC 6633) and Gram negative [A4] plant pathogenic bacteria (Ralstonia solanacearum, Xanthomonas campestris pv. vesicatoria) with the MIC ranging from 16-32 µg/ml. It also showed an unprecedented antimicrobial activity against Mycobacterium tuberculosis H37Ra strain with the MIC ranging from 12.5-25.0 [KKU5] µg/ml. In addition, the result of time kill assay revealed that helvolic acid was bacteriostatic, which inhibited the growth of pathogenic bacteria at 2 fold of MIC. As a result of irregular-shaped cell division was observed by scanning electron microscopy.