Bioactive Metabolites from Aspergillus niger Associated with Moringa oleifera: Potential for Anti-Infective Agents

Abstract

This study explores the metabolic profiling of secondary metabolites from the endophytic fungus Aspergillus niger associated with the medicinal plant Moringa oleifera for the discovery of anti-infective agents. Aspergillus niger was isolated and characterised based on morphological traits and molecular phylogenetic analysis, confirmed via nucleotide sequence comparison with sequences on the NCBI database. The effects of cultivation parameters – including medium composition, volume, extraction solvent, and cultivation duration – on metabolite recovery and biological activity were evaluated. Bioassays identified active extracts, which were further fractionated and purified using chromatographic techniques. Mass spectrometry and nuclear magnetic resonance spectroscopy were employed to analyse the isolated metabolites. The results demonstrated that cultivation conditions significantly influenced metabolite production and extract recovery. The study revealed notable antibacterial and antifungal activities against Escherichia coli, Staphylococcus aureus, and Candida albicans among others, although no significant anti-leishmanial, antioxidant, or anti-inflammatory effects were observed. Metabolites identified include fumaric acid, succinic acid, 4-(2-hydroxyethyl)phenol, 5-hydroxymethyl-2-furancarboxylic acid, 4-hydroxybenzoic acid, and N-[2-(4-hydroxyphenyl)ethyl]acetamide. Notably, this study marks the first report of 4-(2-hydroxyethyl)phenol and N-[2-(4-hydroxyphenyl)ethyl]acetamide as isolated from Aspergillus niger. These findings highlight Aspergillus niger as a promising source of bioactive metabolites and provide valuable insights into its potential for the development of novel anti-infective agents.