Cytotoxic and antimicrobial effects induced by ethyl acetate extracts of Malaysian endophytic fungi (MKS 3, MPL 2 & MPRRW 2.3.1)

Endophytes are microorganisms that live within healthy tissues of plants without causing any apparent symptoms of diseases. There is increasing evidence indicating endophytes as rich source of natural, novel bioactive compounds against cancers and infectious diseases. Capitalizing on the abundance of unexplored Malaysian endophytes that reside in marine plants, the present study was conducted to assess the cytotoxic and antimicrobial potential of ethyl acetate extracts of 3 endophytic fungi isolated from Terminalia sp. ("Ketapang" tree) and Sonneratia sp. ("Perepat" tree) plants. Another 2 marine fungi (SM 1.4 and SW 2.1 Plate 2) were also included for comparison purposes. For cytotoxic assay, HCT 116 (human colorectal carcinoma cells) were seeded at 2,500 cells/ 200µL and incubated overnight. The cancer cells were then treated with extracts (0.01 - 100 µg/mL) for 72 h. SRB assay was performed to generate dose-response curve from which the ICso (Inhibitory concentration of the response is reduced by half) was determined. The anti­ bacterial assay involved addition of pathogenic bacteria (Gram-positive and negative) into extracts (0.01 - lOOµg/mL) prior to determination of the minimal inhibitory concentration (MIC). The present findings indicated the Terminalia-derived MKS 3 as the most potent endophytic fungal extracts against HCT 116 with ICso observed at 2.5 µg/mL. Its cytotoxicity, however, was 5 times less potent when compared to that of 5-FU, the positive control. The Sonneratia-derived MPRRW 2.3.1, yet another endophytic fungal extract, emerged as the most potent antibacterial agent against Staphylococcus aureus and Pseudomonas aeruginosa with MIC observed at 0.1 mg/mL. Its potency were 10 fold and 2.5 fold lower than that of gentarnicin, the positive control against P aeruginosa and S. aureus, respectively. Comparatively, both the marine fungal extracts elicited modest cytotoxic and antimicrobial activities. The present study has successfully identified MKS 3 and MPRRW 2.3.1 as potential cytotoxic and antimicrobial agents, respectively. These two lead extracts should be subjected to isolation of pure compound for in depth anticancer and antimicrobial studies in the future.