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Email:
Vatcharin Rukachaisirikul· - [email protected]
Keywords:
antimicrobial activity; cytotoxic activity; y-lactone; soil-derived fungus; sesquiterpene; Tríchoderma citrinoviride
Abstract
Two new sesquiterpenes, trichocitrinovirenes A (1) and B (2). and five known compounds including four structurally related sesquiterpenes and one y-lactone were isolated from the soil-derived fungus Trichoderma citrinoviride PSU-SPSF346. The structures were identified by analysis of their spectroscopic data. The relative configuration was assigned based on NOEDIFF data. The absolute configuration of compound 1 was established according to specific rotations and ECD data while that of compound 2 was proposed based on biosynthetic considerations. Compound 2 possesses a rare bicyclic sesquiterpene skeleton. The antimicrobial and cytotoxic activities of the isolated compounds were evaluated.
Introduction
The fungus Tríchoderma citrinoviride produces structurally diverse secondary metabolites including diterpenes [1.2], alkaloids [3], sorbicillinoids [4.5], long chain alcohols [6], and cyclonerane sesquiterpenes [7]. Some of them display rial [1.2.7], [3], anti-inflammatory [4], and antimicroalgal [7] activities. Based on these data, the investigation of secondary metabolites from this fungus is still limited. In our ongoing search for antimicrobial secondary metabolites from soil-derived fungi. T. citrinoviride PSU-SPSF346 was isolated from a soil sample collected from the Sirindhorn Peat Swamp Forest. Narathiwat Province. Thailand. The crude mycelial extract of T. citrinoviride PSU-SPSF346 displayed antimicrobial activities against Staphylococcus aureus, methicillin-resistant .S', aureus, and Cryptococcus neoformans ATCC90113 with MIC values of 128. 200 and 64 µg/mL. respectively. Herein, we report the isolation and structure elucidation as well as antimicrobial and cytotoxic activities of some isolated compounds which were obtained in sufficient amount.
Results and Discussion
Chemical investigation of the broth and mycelial extracts of T. citrinoviride PSU-SPSF346 by various chromatography techniques led to the isolation of two new sesquiterpenes, trichocitrinovirenes A (1) and B (2). four known structurally related sesquiterpenes including gliocladic acid (3). hydroheptelidic acid (4). and xylaric acids B (5) and D (6) [8], as well as one known y-lactone. fusidilactone A (7) [9] (Figure 1). Their structures were elucidated on the basis of analysis of their spectroscopic data including IR. UV. NMR. and MS. The relative configuration was assigned based on NOEDIFF data. Furthermore, the absolute configuration of compound 1 was determined by comparison of its specific rotation and electronic circular dichroism (ECD) data with those of compound 3. whereas that of compound...