Bioactive Metabolites of Aspergillus neoniger, an Endophyte of the Medicinal Plant Ficus carica

Abstract

Endophytes are considered as a rich source of bioactive natural products. Many plants have not been investigated for their endophytic content yet, such as the medicinal plant Ficus carica. Recent studies confirmed antimicrobial and anticancer activities for the plant extract. To find out if its endophytes contribute to its reported activities, the bioactive endophyte Aspergillus neoniger was selected for investigation of its metabolites since it exerted antimicrobial and anticancer activities in preliminary screening assays. The fungal extract was subjected to bioactivity guided chromatographic fractionation for isolation of its bioactive metabolites. This resulted in the identification of four aurasperones (asperpyrone D, aurasperone D, dianhydroaurasperone C, aurasperone A) through spectroscopic analysis. Aurasperone D and asperpyrone D were found to be cytotoxic against human cervical cancer cells (50 % cytotoxic concentration=4.4 μg ml-1 and 3.0 μg ml-1 respectively). Aurasperone D exerted strong antiproliferative effect against human immortal erythroleukaemia cells 562 and human umbilical vein endothelial cells (concentration at which 50 % growth inhibition achieved is 5.3 and 4.7 μg ml-1) as well as asperpyrone D (concentration at which 50 % growth inhibition achieved is 4.9 and 5.4 μg ml-1). Dianhydroaurasperone C and aurasperone A, on the contrary, showed weak cytotoxic and antiproliferative effects. All compounds were tested for antimicrobial activity against several test strains including the plant pathogen Fusarium oxysporum. Results revealed that aurasperone D and asperpyrone D to be most active which suggests potential protective role of this endophyte on its host plant. These results suggest possible partial contribution of Aspergillus neoniger to the reported activity of the host plant