Evaluation of antibacterial and antifungal properties of 9-oxo-10,11-dehydroageraphorone extracted from Eupatorium adenophorum

Abstract

9-Oxo-10,11-dehydroageraphorone (ODA) is a cadinene sesquiterpene isolated from Eupatorium adenophorum. The antimicrobial activity of ODA was tested in vitro against four fungal strains and four bacterial strains. The fungitoxicity of ODA was evaluated by percentage radial growth inhibition using the poisoned food technique. ODA inhibited Fusarium oxysporum more than the other tested strains, giving EC50 values of 0.325 mg ml−1 at 48 h and 0.365 mg ml−1 at 96 h. Tests also revealed that ODA inhibits the germination of Fusarium oxysporum spores, reducing germination by 97 % at 0.5 mg ml−1 concentration. The minimum inhibitory concentrations (MIC) of ODA against four tested strains of Ralstonia solanacearum ranged from 0.25 to 1 mg ml−1 using a micro-well dilution method. In addition, our scanning electron microscopy study revealed previously unreported, pronounced effects of ODA on Fusarium oxysporum, Bipolaris sorokiniana, Fusarium proliferatum and Alternaria tenuissima, including marked shrinkage in the mycelia of all tested strains, swelling at the ends of Bipolaris sorokiniana mycelia and inhibition of spore production in the strains of Bipolaris sorokiniana and Fusarium proliferatum, providing firm evidence of the toxicity of ODA to these pathogenic fungi.