The antimicrobial activity of the alcohols from Musca domestica

Abstract

Summary The total cuticular alcohols in larvae, male, and female of M. domestica were detected in comparable amounts (4.59, 3.95 and 4.03 µg/g of the insect body, respectively). The total cuticular alcohols in pupae occurred in smaller quantities (2.16 µg/g of the insect body). The major free alcohol in M. domestica larvae was C12:0 (70.4%). Internal alcohols of M. domestica larvae were not found. Among cuticular pupae alcohols, C12:0 (31.0%) was the most abundant compound. Other alcohols were detected in smaller amounts from 3.7% (C14:0) to 14.4% (C16:0). In the internal lipids of pupae, only 5 alcohols were identified in traces. Most abundant alcohol in male was C24:0 (57.5%). The percentage content of cuticular C24:0 in male and female were significantly higher than those of cuticular lipids in larvae and pupae and compromised 57.5%, 36.5%, 0.9% and 5.6%, respectively. Only two alcohols were present in internal lipids of male in traces (C18:0 and C20:0). Most abundant cuticular alcohols in female were C24:0 (36.5%) and C12:0 (26.8%). Other alcohols were present in smaller quantities from 1.5% (C14:0) to 11.9% (C22:0) and two alcohols were present in traces (C26:0 and C28:0). Only two alcohols (C18:0 and C20:0) were detected in comparable amounts in internal lipids of female (3.61±0.32 and 5.01±0.42 µg/g of the insect body, respectively). For isolated alcohols antimicrobial activity against reference strains of bacteria and fungi was determined (Bacillus subtilis ATCC 6633, Rhodococcus equi ATCC 6939, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13882, Proteus vulgaris ATCC 13315, Aspergillus niger ATCC, Candida albicans ATCC 10231, Candida lipolytica PCM 2680, and Candida tropicalis PCM 2681). Individual alcohols have shown approximately equal activity against fungal strains. C14:0 was effective against gram-positive bacteria, while gram-negative bacteria were resistant to all tested alcohols. Mixtures of alcohols found in cuticular lipids of larvae, pupae, male and female of M. domestica presented in general higher antimicrobial activity in comparison to individual alcohols. In contrast, crude extracts containing both, cuticular and internal lipids, showed no antifungal activity against entomopathogenic fungus C. coronatus efficiently killing adult house flies (but not larvae and pupae).