Antifungal susceptibility profile of Fusarium species to defensive secretion of millipede Pachyiulus hungaricus (Karsch, 1881) (Diplopoda, Julida, Julidae)

Abstract

Research into susceptibility of Fusarium species to natural products of various origin is nowadays of considerable interest given their world-wide distribution, mycotoxins synthesis and importance to food safety in crop production. Principal purpose of this study was to in vitro assess anti-Fusarim properties of ethanol (EtOH), methanol (MetOH), hexane (Hex), and dichloromethane (DCM) extracts of Pachyiulus hungaricus defensive secretion, in range of concentrations of from 0.05 to 0.6 mg mL-1, against seven Fusarium species known to produce toxic metabolites (trichotecenes, fumonisins and zearalenone) and cause root and stem rots, vascular wilts, fruit root, and infect seed. Strongest activity was observed for EtOH extract, with minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC) in the range of from 0.15 to 0.32 mg mL-1 and 0.15 to 0.44 mg mL-1, respectively. Hex and DCM extracts were shown to possess weakest antifungal potential, though stronger compared to antimycotic Nystatin (MIC and MFC >0.60 mg mL-1, not determined). Fusarium avenaceum was the most susceptible fungus, while F. graminearum and F. sporotrichioides demonstrated the greatest degree of resistance to tested extracts. Such pronounced antifungal property of studied julidan defensive secretion is probably due to the presence of quinones (p-benzoquinone and its derivatives), as well as complex interactions of dominant quinones with less abundant esters (pentyl and hexyl esters of C14-C18 saturated and unsaturated carboxylic acids).