Thesis (M.Sc.)--Chulalongkorn University, 2004

The purpose of this research was to isolate bioactive compounds from endophytic fungi isolated from Croton oblongifolius leaves in Kanchanaburi province. The endophytic fungi were isolated using surface-sterilization technique and obtained 72 isolates including Bipolaris sp., Fusarium sp., Phomopis sp. and members of Xylariaceae. All isolates were examined antimicrobial activity using dual culture agar diffusion technique. The results showed that 15% of the fungi inhibited only bacteria, 8% of the fungi inhibited only yeast, 9.7% of the fungi inhibited bacteria and yeast, and 67% of the fungi exhibited no activity. Isolate KBLM02 was selected for the study because it exhibited activity against Bacillus subtilis, Staphylococcus aureus and Candida albicans with inhibition clear zone 10, 11, and 14.5 mm, respectively. Based on morphology and nucleotide sequencing of ITS regions of rDNA, isolate KBLM02 was identified as Gibberella moniliformis (Telemorph)or Fusarium verticillioides (Anamorph). Sabourauds Dextrose culture broth of the isolate KBLM02 was isolated by extraction, chromatographic technique and crystallization to give 4 compounds and a mixture. On the basis of physical properties and spectroscopic data, they were elucidated as a mixture of fusaric acid 1 and dehydrofusaric acid 2, dehydrofusaric acid, 8-O-methylbostrycoidin 3, 4[alpha],5-epoxy-7,22(E)-ergostadien-3[beta]-ol 4 and bikaverin 5. Antimicrobial activities of these compounds were investigated. Compound 2, 3, 4, 5 and a mixture of 1 and 2 showed activity against Bacillus subtilis with MIC 3.95 (22.3), 7.81 (26.1), 250 (606.8), 125 (327.2) and 15.62 microgram/ml (micrometre), respectively. Compound 3, 5 and a mixture of 1 and 2 showed activity against Staphylococcus aureus with MIC 15.62 (52.2), 7.81 (20.4) and 31.25 microgram/ml (micrometre), respectively. Compound 4, 5 and a mixture of 1 and 2 showed activity against Escherichia coli with MIC 250 (606.8), 7.81 (20.4) and 250 microgram/ml (micrometre), respectively. Compound 2 and 4 showed activity against Pseudomonas aeruginosa with MIC 3.95 (22.3) and 3.95 (9.59) microgram/ml (micrometre), respectively. Compound 4 and a mixture of 1 and 2 showed activity against Candida albicans with MIC 250 (606.8) and 250 microgram/ml (micrometre), respectively. Additionally, compound 3 exhibited cytotoxic activity against HEP-G2 and KATO-3 with IC[subscript 50] 9.5 (31.8) microgram/ml (micrometre)