Isolation and Characterization of Antibacterial Carotane Sesquiterpenes from <i>Artemisia argyi</i> Associated Endophytic <i>Trichoderma virens</i> QA-8

• Main Authors: Xiao-Shan Shi, Yin-Ping Song, Ling-Hong Meng, Sui-Qun Yang, Dun-Jia Wang, Xing-Wang Zhou, Nai-Yun Ji, Bin-Gui Wang, Xiao-Ming Li
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Antibiotics
• Subjects: <i>Artemisia argyi</i>; endophytic fungus; <i>Trichoderma virens</i>; carotane sesquiterpenes; antibacterial activity
• Online Access: https://www.mdpi.com/2079-6382/10/2/213

Carotane sesquiterpenes are commonly found in plants but are infrequently reported in the fungal kingdom. Chemical investigation of <i>Trichoderma virens</i> QA-8, an endophytic fungus associated with the inner root tissue of the grown medicinal herb<i> Artemisia argyi</i> H. Lév. and Vaniot, resulted in the isolation and characterization of five new carotane sesquiterpenes trichocarotins I–M (<b>1</b>–<b>5</b>), which have diverse substitution patterns, and seven known related analogues (<b>6</b>–<b>12</b>). The structures of these compounds were established on the basis of a detailed interpretation of their NMR and mass spectroscopic data, and the structures including the relative and absolute configurations of compounds <b>1</b>–<b>3</b>, <b>5</b>, <b>9</b>, and <b>10</b> were confirmed by X-ray crystallographic analysis. In the antibacterial assays, all isolates exhibited potent activity against <i>Escherichia coli</i> EMBLC-1, with MIC values ranging from 0.5 to 32 µg/mL, while 7<i>β</i>-hydroxy CAF-603 (<b>7</b>) strongly inhibited <i>Micrococcus luteus</i> QDIO-3 (MIC = 0.5 µg/mL). Structure-activity relationships of these compounds were discussed. The results from this study demonstrate that the endophytic fungus <i>T. virens</i> QA-8 from the planted medicinal herb <i>A. argyi</i> is a rich source of antibacterial carotane sesquiterpenes, and some of them might be interesting for further study to be developed as novel antibacterial agents.