Metabolites of endophytic Colletotrichum gloeosporioides isolated from leaves of Carica papaya

Abstract

Endophytic fungi associated with Nigerian plants have recently generated significant interest in drug discovery programmes due to their immense potential to contribute to the discovery of new bioactive compounds. This study was carried out to investigate the secondary metabolites of endophytic Colletotrichum gloeosporioidesisolated from leaves of Carica papaya. The plants were collected from Agulu, Anambra State, Nigeria. Endophytic fungal isolation; identification by DNA amplification and sequencing of the fungal internal transcribed spacer (ITS) region; fungal fermentation; and extraction of secondary metabolites were carried out using standard methods. The crude extract was tested for antimicrobial, antioxidant and cytotoxic activities. Also, the extract was subjected to high performance liquid chromatography (HPLC) analysis to identify its constituents. In the bioassay, C. gloeosporioidesextract only exhibited antibacterial activity against Klebsiella pneumoniae. The extract showed moderate antioxidant activity in the 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) assay with an inhibition of 28.2% at a concentration of 500 µg/mL. At a concentration of 100 µg/mL, the fungal extract showed moderate cytotoxic activity against cisplatin-sensitive ovarian cancer cell line 2780 (sens) and cisplatin-resistant ovarian cancer cell line 2780 (CisR) with growth inhibitions of 35.42 and 15.7% respectively. HPLC analysis of the extract revealed the presence of 3 bioactive compounds Aureonitol, protocathechuic acid, and Glucobrassicin in the crude extract of C. gloeosporioides. The findings of this study revealed the potentials possessed by C. papaya as source of entophytes that express biological active compounds. These endophytes hold key of possibilities to the discovery of novel molecules for pharmaceutical, agricultural and applications.