The anti-pseudomonal potentials of metabolites from some endophytic fungi isolated from Garcinia kola leaves

Abstract

The morbidity and mortality rates from Pseudomonas aeruginosa infections are increasing, due to the development of drug-resistant strains. This study aimed to explore the secondary metabolites of endophytic fungi of Garcinia kola for their antibacterial activities against P. aeruginosa. The endophytic fungi associated with healthy leaves of G. kola were isolated using the standard methods. These fungi were subjected to solid-state fermentation on rice media at 28oC for 21 d. The fungal secondary metabolites were extracted using ethyl acetate, and then concentrated under vacuum. The fungal crude extracts were screened for their antibacterial activities against clinical and laboratory strains of P. aeruginosa, using the agar diffusion method. The bioactive components of the fungal extracts were identified using High-Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD) analysis. Three endophytic fungi mainly; Aspergillus sp., Fusarium sp. and Colletotrichum sp. were isolated. At concentration of 1 mg/ml, extracts of the three fungi displayed anti-pseudomonal activities against all the isolates, except for a P. aeruginosa isolate recovered from urine. Results of the HPLC-DAD analysis revealed the presence of several active compounds such as; indole-3-acetic acid, p-hydroxybenzoic acid, and protocatechuic acid, among others in the fungal extracts. These compounds have been previously reported to have significant antimicrobial properties. This study reveals that endophytic fungi associated with G. kola leaves possess promising anti-pseudomonal potential.