Studies On The Isolation And Characterization Of Two Endophytic Fungi From Halophytic Salicornia Bigelovii Torr. And Its Secondary Metabolites

Endophytic fungi thrived in the high-salt environment form special physiological structure and metabolic mechanisms in the long process of natural selection and evolution, and have the capability to produce special secondary metabolites with novel structures and unique bioactivities which have important applications in the field of pharmaceutical, food, chemical engineering, agricultural production and so on. They have become a potential resource to seek the new natural products. In this study, the endophytic halotolerant fungi from Salicornia bigelovii were isolated, identified and fermented. Its fermentation products were separated and identified using modern separation and spectroscopic techniques, and were conducted a preliminary evaluation on the biological activities.Two endophytic halotolerant fungi coded Salicorn 5 and Salicorn 8 were isolated and purified from Salicornia bigelovii by the PDA plate culture. Salicorn 5 was identified as a new species of Cunninghamella sp., named Cunninghamella bigelovii Z. Xin, Y. Zhao et H. Wang sp. nov., Salicorn 8 was identified as Fusarium equiseti by morphological study and molecular analysis.The strain Salicorn 8 was largely fermented. The fermentation product was extracted and separated by silica gel column chromatography and Sephadex LH-20. A new glucitol, diglucotol (1), together with ten known compounds, Cerebroside C (2), Nb-acetyltryptamine (3),3β,5α,9α-trihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (4), stigmasta-7,22-diene-3β, 5α,6α-triol (5), cerevisterol (6), ergosterol peroxide (7), campesteryl glucoside (8), I-oxo-7a-hydroxysitosterol (9), oleic acid (10), linoleic acid (11), were identified using modern spectroscopic techniques such as infrared (IR), mass spectrometry (MS) and nuclear magnetic resonance (1H,13C,1H-1H COSY, HSQC and HMBC NMR).The antioxidant activities of the 11 compounds above were assayed by DPPH radical scavenging method. Results showed that cerebroside C (2) had antioxidant activity, and the maximum scavenging rate on DPPH was 87.51% in the tested concentration. MTT method was used to evaluate the anti-tumor activities of compound 1, indicating that diglucotol (1) exhibited weak antiproliferative activities towards MCF-7 human breast cancer cell, MDA-MB-231 human breast cancer cell and Caco-2 human colon cancer cell with EC50 values of 97.56,92.35 and 99.39 μM, respectively.