Characterization and antimicrobial activities of bioactive compounds from endophytic Trichoderma asperellum isolated from Dendrobium orchids

Endophytic Trichoderma asperellum (D7) from Dendrobium orchids was explored for its antimicrobial potential through characterization and identification of bioactive compounds. Bio-guided fractionation of crude extracts of T. asperellum (D7) afforded 7 fractions with antimicrobial activities against bacterial pathogens (Bacillus cereus and Pseudomonas aeruginosa) and a plant pathogen (Ganoderma boninense). Among the fractionated extracts, fraction 1 was most effective towards P. aeruginosa (MIC: 1.25 mg/mL) while fraction 4 had the strongest inhibitory activities against B. cereus (MIC: 2.5 mg/mL) and G. boninense (50.62% inhibition). Liquid chromatography-mass spectrometry (LCMS) analysis led to the identification of antimicrobial compounds from fraction 1 (paeoniflorin, kanzonol N, 2-nonynoic acid, fenpropidin, (+)-tetrandrine, 12(13)-EpOME-d, rifamycin, linoleic acid(d4) and 3 alpha,12 alpha-dihydroxy-5 beta-chol-8(14)-en-24-oic acid) and fraction 4 (morpholine, epothilone A, tetroquinone, loperamide, 2,5-dimethoxycinnamic acid, 3,4-dihydroxyphenyl ethanol, pyropheophorbide A, streptomycin, 5-hydroxystreptomycin, rifamycin, leucomycin A1, sophoradiol, 5R-hydroxy-hexanoic acid, 2-undecanol, 3-methyl-2-quinoxalinone, scandenin and lumichrome) of T. asperellum (D7). Several of the antimicrobial compounds were revealed for the first time for endophytic T. asperellum (D7). The identification of bioactive compounds from T. asperellum (D7) would contribute to the development of natural antimicrobials, agrochemicals, fungicides and pesticides.