Metabolites Of Marine Sponge Fungi Myrothecium Verrucaria HMP-F73 And Their Bioactivities

Sponges are widely distributed with wide varieties, and could produce a large number of biologically active substances. Among the marine natural products reported, 40.6 % of them were isolated from sponge. Recent studies suggest that some sponge natural products were produced by their symbiotic microbe. Due to the difficulty for collecting sponge and their lower level of active ingredient, cultivation of sponge symbiotic microbe in large scale cultivation was a plausible way to produce valuable natural products. So the research on chemical constituents from sponge symbiotic microbe has become popular in marine natural products.This thesis was planned to screening insecticidal microbe from sponge symbiotic microbe resources, in order to find potentially insecticidal agents. As a result, a strain Hmp-F73 was selected and identified as Myrothecium verrucaria according to the Brine Shrimp insecticidal assay on 96 fungal strains derived from sponge. When the concentration of the methanolic extract of Hmp-F73 was 0.25μg/mL, the corrected mortality was 100.00 %. The methanolic extract was portioned with silica gel column chromatography, and 7 fractions were obtained. At the concentration of 400μg/mL of fraction 3, it could inhibit the feeding of Spodoptera exigu by the rate of 85.25 %. The fraction 6 at 1 mg/mL also demonstrated significant inhibition activity against Rhizoctonia solani with 9.25 mm of inhibition zone. Seven macrocyclic trichothecenes were purified by tracking the activity: Verrucarin J (Compound 1), Isororidin E (2), Roridin E (3), 8-acetoxyroridin H (4), 8-hydroxyverrucarin J (5), Trichoverrin B (6), Verrucarin A (7). All the metabolites displayed potent toxic activity with LC50 values ranging from 0.001μg/mL to 1.138μg/ml. And all the compounds showed no toxicity on lettuce seeds at 1μg/ml, while a weak toxicity at 100μg/ml.Trichothecenes comprise a group of sesquiterpenes characterized structurally by the 12, 13-epoxy-trichothec-9-ene moiety. However, there are few report related with insecticidal activity of these mycotoxins. This thesis found that the marine fungus Hmp-F73 could be considered as a resource of microbial pesticide without toxicity to plants. In this study we have investigated the production, the chemical purification, and the chemical and biological characterization of the metabolites produced by Myrothecium verrucaria. A preliminary structure–activity relationship of the insecticidal trichothecenes was highlighted in brief.