Study On Secondary Metabolites Of Three Endophytic Fungal Strains

Endophytic fungi are commonly found in healthy plant tissues with various of species. They can produce many secondary metabolites in a variety of biological activity and structural types, including terpenoids, alkaloids, quinones, flavonoids and sterols, many of these compounds have antimicrobial, insecticidal, anti-tumor and anti-viral activities.Our previous study had carried out the bioactive screening of the endophyte fungi. Among them, three strains YE3016, YE3048 and YM355364 have potent activities. On the basis of the previous work, we studied on the chemical constituents of the fermentation product of these strains. The main results are as follows:Two strains YE3048 and YE3016 were identified as Talaromyces wortmannii and Chaetomium globosumm respectively based on the analysis of their ITS sequences, combined with fungal morphologic characteristics. The strain YM355364 had been identified as Phomopsis sp. during previous work.The fermentation extracts of the bioactive strains were isolated and purified by various column chromatography on silica gel, RP-18, and Sephadex LH-20. The chemical structures of the compounds were identified on the basis of extensive NMR and mass spectroscopic analysis. A total of 22 compounds were obtained from the fermentation extracts of three strains. The structures of all the compounds were identified, in which there are four new compounds. These compounds included anthraquinones and their dimers, sterols, phthalides, chaetoglobosin and other types. Parts of the compounds were detected against tumor cells, and three compounds have moderate anti-tumor activity.Seven compounds were isolated and identified from the fermentation extract of the strain YE3016. Compound 1 is new, named as 3-demethyl-3-(2-hydroxypropyl)-skyrin. The other compounds were identified as skyrin (2), oxyskyrin (3), emodin (4), 1,3,6-trihydroxy-8-methyl-anthraquinone (5), ergosterol (6) and β-sitosterol (7), respectively. Compounds 1-3 are anthraquinone dimers, and compounds 4 and 5 are belonging to anthraquinones.Compound 2 was only reported its’H-NMR data before, we supplied its 13C-NMR data here. Compounds 1-3 showed moderate inhibitory activity aganist human breast cancer MCF-7 cells with IC50 values of 20.76 ± 3.41,19.21 ± 3.85 and 9.83 ± 4.21 μg/ml respectively.A total of 12 compounds were isolated and identified from the fermentation extract of the strain YE3048. Compounds 1-3 were new, and named as phomopsinolide A (1), phomopsinolide B (2), phomopsinolide C (3). The other nine known compounds were identified as diaporthelactone (4), isosclerone (5), 4,8-dihydroxy-6-methoxy-3,4-dihydro-2H-naphthalen-l-one (6), pestalotiopsone B(7), (R)-phomotone(8),5-hydroxy-7-methoxy-4,6-dimethylphthalide(9), convolvulol(10), convolvulanic acid B (11), (S)-phomotone (12).Three compounds were isolated and identified from the fermentation extract of the strain YE3048. These compounds were identified as ergosterol peroxide (1), chaetoglobosin E (2), chaetoglobosin Vb (3). Compounds 2 and 3 are characteristic secondary metabolites of Chaetomium globosum.