This study aimed to investigate the in vitro toxicity activity of ethyl acetate extracts of endophytic fungi isolated from soursop leaves (Annona muricata L.) against colon cancer and analyse the bioactive compounds from the fungal extract with best anticancer activity using Gas Chromatograph-Mass Spectrometer (GC-MS). The experimental design used was a completely randomized factorial design with two factors, the type and concentration of endophytic fungi extract. Industrial Microbiology Laboratory of Biology Research Center, Indonesian Institute of Sciences (LIPI) Cibinong-Bogor, Laboratory of Microbiology and Immunology of Center for Animal and Primate Studies of Bogor Agricultural University and Center of Forensic Laboratory, conducted from March 2016 to March 2017. Cytotoxic property was determined using 3-(4,5- dimethylthiazol-2-yl)-2,5- diphenyltetrazoliumbromide (MTT) assay method. Entophytes were extracted using ethyl acetate solvent. Extract of ten isolates (at concentration of 100 μg/mL) were examined for the inhibition effect to WiDr cancer cells. Five isolates that showed significantly high inhibition effect (P<0.05) were further selected for IC50 determination against WiDr cell lines at extract concentration of 25, 50, 100, 200 and 400 μg/mL. Three isolates that significantly showed high activity (P<0.05) were chosen, and then measured for their toxicity (IC50 value) to normal cell (Chang cell lines) at concentration of 25, 50, 100, 200 and 400 μg/mL. The bioactive compound of the isolate which had the lowest toxicity to normal cell was then analysed using GC-MS. Fungal extracts of ten isolates were examined for their cytotoxicity to WiDr cancer cells with the result showed that isolate of Sir-CA1, Sir-CA2, Sir-G2, Sir-G4 and Sir-SM2 had high inhibitions. From the five fungal extracts, isolate of Sir-CA1, Sir-G2 and Sir-SM2 showed high cytotoxicity to WiDr cancer cell. Among the three isolats, fungal extract of isolate from Sukabumi (Sir-SM2) showed the lowest toxicity to normal cell was analysed on secondary metabolite compounds using GC-MS. The fungal extract contained ester group, alkaloid, saturated fatty acid, unsaturated fatty acid, terpene, terpenoid and aromatic compounds. Ethyl acetate extracts of endophytic fungi Sir-SM2 isolated from soursop leaves (Annona muricata L.) had high cytotoxic effect on colon cancer cell (IC50=20.80 μg/mL) and the lowest toxicity to normal cell compared with other fungal extracts (IC50=63.69 μg/mL). The analysis of bioactive compounds with GC-MS showed that fungal extract of isolate Sir- SM2 contained compounds such as alkaloid, saturated fatty acid, unsaturated fatty acid, terpene and terpenoid that had function as anticancer. Annual Research & Review in Biology, Vol. 18, No. 5. Hal. 1-11 ISSN 2347-565X
