Biologically active compounds from endophytic fungi isolated from Croton oblongifilius in Chachoengsao Province

Abstract

Eighty-four isolates of endophytic fungi were isolated from leaves, petrioles, twigs, and barks of Croton oblongifolius in Chachoengsao Province. Only seven strains produced antimicrobial metabolites against bacteria and yeasts with lesser activity. The strains CsLm 08 and CsPm 09 were selected for further studied. Based on morphology, physiology, cultural characteristics and nucleotide sequence of ITS regions, the strains CsLm 08 and CsPm 09 were Lasiodiplodia theobromae and Emericella variecolor, respectively. Isolation of mycelium ethyl acetate crude of Lasiodiplodia theobromae gave ergosta-5,22-dien-3-ol, C[subscript 22]-C[subscript 24] long chain carboxylic acid, and lasiodiplodin. The ethyl acetate crude of fermentation broth of Emericella variecolor gave terrein and the ethyl acetate crude of mycelium gave five compounds including stellatic acid and four xanthone derivatives consisting of; shamixanthone, 14-methoxy-tajixanthone-25-acetate, tajixanthone hydrate and a novel xanthone derivative, 8-(3-Hydroxy-2-methoxy-3-methylbutyl)-1,11-dihydroxy-2-isopropenyl-5-methyl-2,3-dihydro-1H-pyrano[3,2a]-xanthen-12-one. These structures were established on basis of physical properties and detail analyses of spectroscopic data. These compounds were tested for cytotoxicity against human cancer cell lines; HEP-G2 (hepatoma), CHAGO (lung), SW 620 (colon), KATO-3 (gastric) and BT 474 (breast). Tajixanthone exhibited highest activity against HEP-G2 (hepatoma), SW 620 (colon), CHAGO (lung) and KATO-3 (gastric) cancer cell lines with IC[subscript 50] 16.4, 13.6, 11.6, 10.9 nM, respectively and 14-methoxy-tajixanthone-25-acetate exhibited highest activity against BT 474 with IC[subscript 50] 12.1 nM. The novel compound exhibited against SW 620 (colon), KATO-3 (gastric) and BT 474 (breast) cancer cell lines in moderate level with IC[subscript 50] 19.2, 17.2, 20.0 and 14.1 nM, respectively. Furthermore, this represents the first report of cytotoxicity test of lasiodiplodin which was the main product of Lasiodiplodia theobromae.