An endophytic fungus KBLM13, isolated from Croton obtogifolius in Kanchanaburi Province was produced antimicrobial compounds. Morphology of this fungi indicated that it was in genus xylaria. The endophyte KBLM13 was fermented on Sabouraud's Dextrose Broth (SDB) and followed by extraction and isolation antimicrobial compounds using chromatographic techniques and crystallization. Three compounds were received including two new natural products, (S)-(+) mellein methyl ether and Cyclo [Gly- (S) -Pro] from ethyl acetate extract of mycelia and culture broth, respectively and Cyclo- (L) Pro (L) -Val from ethyl acetate of culture Antimicrobial activity of three compounds was determined by The Minimum Inhibitory Concentration Method (MIC). results showed (S) - (+) meilein methyl ether exhibited against B. subtilis ATCC 6633 and S. aureus ATCC 25923 with MIC value of 62.5 (325.18) µg/ml (µM), Cyclo- (L) -Pro- (L) -Val showed against B. subtilis ATC C 6633 with MIC value of 7. 82 (39. 86) µg/ml (µM) and Cyclo [Gly- (S)-Pro] showed against B. subtilis ATCC 6633 and S. aureus with MIC value of 125 (811.16) µg/ml (µM).
