Study On RE5 Active Metabolites Of Endophytic Fungi From Glycyrrhiza

Glycyrrhiza uralensis, a frequently used herb, which has many kinds of bioactive constituents and the value of clinical application for a long history, It has been identified as an endangered medicinal plant because of excessive exploitation.Many studies confirmed that endophytic fungi in plants could produce the same, similar or new active metabolites as their hosts. The production of bioactive compounds by endophytes, especially those exclusive to heir host plants, is not only important from an ecological perspective but also from a new medicine.In this paper, an endophytic fungi named RE5 which isolated from the root of Glycyrrhiza uralensis was chosen as the research object, its fermentation conditions and its secondary metabolites with antibacterial were studied. Conclusions were as follows:The single factor experiments were used with orthogonal experiment to optimize the fermentation condition of RE5 strain with Acinetobacter baummanii as test bacterial. The optimized results employed the glucose of carbon source was2.0%, the peptone of Nitrogen source was 1%, the inoculation amount was 5%, the initial pH value was 7.0, the fermentation temperature was 28℃, speed of shaker was 140 r·min-1, fermentation volumn was set at 50%, the fermentation time was 14d. The diameter of antimicrobial activity in the best fermentation condition is increased to 28.3±0.5mm than which in initial fermentation condition.Under the optimal process conditions, RE5 strain was fermented in liquid PDA medium, then the fermentation broth was separated and purified by macroporous resin, silica gel column chromatography, thin-layer chromatography (TLC) and recrystallization. There compounds were obtained from the bioactive part, which were named crystal A, crystal B and crystal D.The structures of three compounds were analyzed by means of HPLC, IR 1H-NMR,13C-NMR and LC-MS. Crystal D could be (R)-6-Hydroxymellein, but the structure of Crystal A and Crystal B can not be determined for little amount.Three compounds were screened on antimicrobial activity against 10 strains instruction bacteria and 1 strain instruction fungi by filter paper method. It was showed that crystal A had antimicrobial activity against 5 strains, crystal B had antimicrobial activity against 7 strains, and crystal D had antimicrobial activity against 5 strains.