Isolation and screening of secondary metabolites from endophytic fungi of Vernonia amygdalina and Carica papaya for their cytotoxic activity

Searching for cytotoxic compounds from endophytic fungi is a promising way to meet the public health burden posed by cancer, both in developed and developing countries. This study was carried out to evaluate the potential cytotoxic property of secondary metabolites produced by endophytic fungi isolated from Vernonia amygdalina Delile and Carica papaya L. Isolation of endophytic fungi from plant leaves was carried out using standard methods. Solid state fermentation was carried out in rice medium for 21 days at 25 – 27 °C and the secondary metabolites were extracted using ethyl acetate. The extracts were screened for cytotoxicity against L5178Y mouse lymphoma cells using the MTT assay. High-performance liquid chromatography coupled to photodiode array detection (HPLC-DAD) was used to identify the compounds which may be responsible for the recorded cytotoxic activity. A total of ten endophytic fungi were isolated from the leaves of V. amygdalina and C. papaya. Of all the extracts produced by the ten fungi, only one (Cp1) from C. papaya recorded cytotoxic activity. At 10 µg/mL, Cp1, showed a significant cytotoxicity activity against the cancer cells, having an inhibition of 70.8% while the other extracts had no anticancer effect on the cells. HPLC-DAD analysis of the fungal extracts revealed the presence of cytotoxic compounds (catechin, kahalalide and palitantin) present in Cp1 extract. The result indicates the potential of endophytic fungi from C. papaya to produce bioactive compounds with cytotoxic/anticancer properties.