Investigation On The Secondary Metabolites Of Two Characteristic Symbiotic Fungi

The green Chinese onion(Allium fistulosum), which is a perennial species and acrid in taste, is an important spice and vegetable in Asia. Although the green Chinese onion is an important spice and vegetable and exhibits various physiological effects, no study has focused on secondary metabolites of its endophytic fungi, which capture our attention. Consequently, 6 purified strains had been isolated from the green Chinese onion. A candidate(Talaromyces pinophilus AF-02) was chosed as the top strain with the strains crude extracts by the analysis of fungal fermentation conditions and the data of TLC(thin layer chromatography). As the species Talaromyces have many important uses in the industrial and agricultural production, and few studies have focused on T. pinophilus, we investigate the secondary metabolites of the strain. 16 compounds were obtained from the methanolic extracts of this fungus by means of column chromatography, preparative TLC and HPLC. Their structures were determined via extensive NMR, UV, IR, HR-ESI-MS, CD spectroscopic analyses along with the X-ray diffraction data, and comparison with the literature. It contained 4 phthalides derivatives(Tp-1–Tp-4), 6 benzene derivatives(Tp-5–Tp-10), 2 long-chain dicarboxylic acids(Tp-11 and Tp-12), a lactone(Tp-13) and 3 diketopiperazines(Tp-14–Tp-16). There were three new phthalide derivatives with a novel linkage position between the phenyl and phthalide moieties, talaromycolides A-C, Tp-1–Tp-3; and a new long-chain dicarboxylic acid, Tp-11.The same as the microorganisms from animals and plants, soil microbe can also produce abundant compounds with novel structures and variety of activities. No study has focused on the fungi from the soil of the Yellow River. 7 purified strains had been collected from the soil of the bank of the Yellow River in Lanzhou, Gansu, China, and the fungal strain Clonostachys rosea YRS-06 was chosed as the top strain by the analysis of fungal fermentation conditions and the data of TLC. The fungus C. rosea is a common saprophyte in soil and used as a biological control agent. 15 compounds were obtained from the methanolic extracts of this fungus, including 6 bisorbicillinoids derivatives(Cr-1–Cr-6), 3 benzene derivatives(Cr-7–Cr-9), 2 sterides(Cr-10 and Cr-11), a polyalcohol(Cr-12) and 3 carbohydrates(Cr-13–Cr-15). Cr-1–Cr-3 were rare bisorbicillinoids with a γ-pyrone moiety and an open-ended cage structure.The biological properties of Tp-1–Tp-16 and Cr-1–Cr-15 were evaluated against six different Gram-positive(Bacillus megaterium, Bacillus subtilis, Clostridium perfringens, Micrococcus tetragenus, and a strain of MRSA(methicillin-resistant Staphylococcus aureus)) and Gram-negative(Escherichia coli) bacteria strains. The results showed that the compounds Tp-1–Tp-3, Tp-5, Cr-2–Cr-5, Cr-14 and Cr-15 exhibited stronger inhibitions against several strains of tested bacteria than the commonly used antibiotics, levofloxacin, erythromycin, ampicillin and streptomycin.In conclusion, being focused on the isolation and the regulatory of fermentation conditions of these strains, the isolation, structure elucidation and antibacterial activity of the secondary metabolites from two strains, 31 variety compounds were yielded. This results enriched the database of natural products, which is of great significance for the rational development and utilization of microbial resources. The structures and bioactivities of the species in Talaromyces genus have been reviewed. It has great reference value.