Isolation of Secondary Metabolites and Melanoma Inhibition Activity of Endophytic Fungi Chaetomium Globosum S10
Endophytes refer to a group of microorganisms that live in healthy plant tissues but do not cause plant infections and diseases. They not only promote plant stress resistance such as salt tolerance, drought tolerance, cold tolerance, and insect resistance, but also contain rich secondary metabolite synthesis gene clusters, which have become an important source for screening structurally diverse natural products. The Dongxiang wild rice (Oryza rufipogon Griffith.) is the northernmost wild rice in the world, only found in Dongxiang County, Jiangxi Province. Due to its long-term wild status and natural selection, it has excellent traits such as stress resistance, disease and pest resistance, cold resistance, drought tolerance, and high yield. Our research group conducted a systematic study on the diversity of endophytic fungi in Dongxiang wild rice in the early stage, and found that it not only contains abundant plant endophytic fungi, but also PKS gene detection and plant pathogen inhibition activity screening results show that it contains abundant active secondary metabolites. Further research is necessary.
This study focuses on a strain of endophytic Chaetomium globosum S10 isolated from wild rice in Dongxiang, and conducts fermentation culture on it. It was preliminarily found that its fermentation broth has certain inhibitory activity on tumor cells. According to literature reports, chaetoglobosin is the main substance used by Chaetoglobosin to inhibit tumor cells. In order to further investigate the compounds with tumor inhibitory activity in the fermentation broth of S10, we isolated and purified their secondary metabolites, identified the structures of the isolated compounds, and conducted melanoma inhibitory activity tests to discover potential active compounds. This is of great significance for enriching the secondary metabolites and functional diversity of Sphingomonas.
C. Globosum is a fungus belonging to the family Trichomycteridae and genus Trichomycetes. It has been classified as such since 1973, when Sekita was transferred from C Since the isolation of Sphingomonas A and B from Globosum, more than 400 structurally novel active secondary metabolites have been discovered in the genus Sphingomonas. These compounds mainly include Sphingomonas, nitrogen-containing ketones, terpenes, esters, flavonoids, isocoumarins, etc. Among them, Sphingomonas and azone compounds account for the vast majority, while other compounds such as isocoumarins are rarely isolated. Only Yan et al. isolated the isocoumarin compound prochaetoviridin A from Sphingomonas derived from Ginkgo biloba. In this study, three azone compounds, chaetomugilin D (3), chaetomugilin S (4), and chaetoviridis A (5), as well as a common alkaloid compound, coumarin A (6), were isolated from the bacterium in 108. At the same time, isocoumarin compound 6-hydroxymellein (2) and naphthoquinone compound 6-O-demethyl-5-deoxyfusarubin (7) were isolated from the fungus in the genus Trichoderma for the first time. 6-Hydroxymellein (2) is a common biosynthetic intermediate, and microorganisms can synthesize numerous structural analogues using it as a precursor. This suggests that the genome of S10 may contain related polyketide synthase (PKS) gene clusters. Further exploration of the secondary metabolites of S10 may lead to the isolation of new structures and activities of compounds.
This study focuses on the fungus C Seven compounds were isolated and purified from Globosum S10, and their biological activities have been extensively reported. Among them, compounds 3 and 4, which are azone compounds such as chaetomugilin D (3), chaetomugilin S (4), and chaetoviri dins A (5), can effectively inhibit the growth of seedlings. For example, compounds 3 and 4 isolated by Wang et al. from a Ginkgo biloba derived fungus have a significant inhibitory effect on seedling growth, and their IC50 is lower than that of the broad-spectrum herbicide glyphosate. Therefore, they need to be developed into natural and environmentally friendly herbicides. Compound 5 exhibits good antifungal activity and has a good inhibitory effect on nuclear disk bacteria. Its preventive and therapeutic effects are comparable to those of the broad-spectrum fungicide carbendazim. Globulin A (6) has also shown good anti-cancer activity. Knudsen et al. found that compound 6 isolated from Penicillium can be used as a potential drug for treating chronic lymphocytic leukemia (CLL). Under simulated lymphoid tissue culture conditions, it also exhibits significant induction of CLL cell apoptosis. At present, there are no reports on the activity of 6-O-demethyl-5-deoxyfusarubin (7), but its analogue sickle cell line has the effect of inhibiting the proliferation of blood tumor cell lines and increasing cell apoptosis. This study evaluated the inhibitory effects of compounds on melanoma B16 cells. The results showed that, except for compound 2, the other six compounds had no inhibitory effect on melanoma B16 cells.
So far, 6-hydroxymellein (2) has only been isolated from the endophytic fungi Daldinia Eschscholtzii and Aspergillus terreus in mangroves, and has been found to have inhibitory effects on Arabidopsis pollen development. In addition, Yang et al found that compound 2 has no inhibitory effect on human breast cancer cell line MDA-MB-231 and human pancreatic cancer cell line PANC-1, but only weak inhibitory activity on non-small cell lung cancer cell line A549 and human liver cancer cell line BEL-7402, with IC50 of 170.6mg/L and 315.0mg/L respectively. This study first found that 6-hydroxymellein (2) has good inhibitory activity on melanoma B16 cells, with an IC50 of 2.24 μ mol/L. Melanoma, as a common skin malignant tumor in clinic, has a high degree of malignancy, is easy to metastasize, and the incidence rate has an increasing trend year by year. Therefore, the discovery of new activity of 6-hydroxymellein (2) is helpful to the research and development of therapeutic drugs for melanoma, and provides a new idea for the development of drugs for treating melanoma.