Isolation, identification, and antibacterial activity study of endophytic fungi in Coptis chinensis Franch. Coptis chinensis belongs to the Ranunculaceae family and Coptis genus. According to the Compendium of Materia Medica, Coptis chinensis has the effects of clearing heat, drying dampness, purging fire, and detoxifying. There are about 18 species of Huanglian plants, of which 6 are domestically produced in China, namely Huanglian, Sanjiaoyou Huanglian, Yunnan Huanglian, Emei Huanglian, Wuye Huanglian, and Wujian Huanglian. One variant is Short sepal Huanglian, and the first three are commonly referred to as “Weilian”, “Yalian”, and “Yunlian”. Sichuan is one of the main production areas of Huanglian. According to the “Biography of Famous Doctors”, “Huanglian was born in Wuyang and the mountains of Shu County, and was harvested in February and August. As early as before the Ming Dynasty, Huanglian was artificially cultivated in the Emei area of Sichuan. Currently, there are GAP Weilian planting bases in the Emei area of Sichuan. The traditional Chinese medicine Huanglian decoction has significant in vitro antibacterial effects on Staphylococcus aureus, Escherichia coli, and other bacteria. The antibacterial mechanism of Huanglian and its active ingredients is complex and diverse, including damaging bacterial cell membranes, inhibiting the synthesis of intracellular macromolecules, blocking bacterial division and development, and interfering with the formation of the Z-ring to inhibit the cell division protein FtsZ.
Endophytic bacteria refer to bacteria or fungi that inhabit plant organs, can settle in internal tissues of plants, and do not cause significant damage to the host. Endophytic bacteria are important new sources of bioactive products in plants. Scholars have isolated the endophytic fungus Cytospora sp. from the pine cone plant Conocarpus erecta, and screened for a new antibacterial compound, Cytosporone D, in its fermentation broth. The compound showed significant antibacterial effects against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Candida albicans. The increasingly severe antibiotic resistance has posed a significant threat to human health, and exploring endophytic fungal resources in medicinal plants is one of the new ways to search for new antibiotics.
As one of the main producing areas of Coptis chinensis, there is still a lack of research on the diversity of endophytic fungi in Sichuan Coptis chinensis. At the same time, there is no research on the antibacterial activity and mechanism of metabolites of endophytic fungi in Coptis chinensis. At present, research on endophytic fungi of Coptis chinensis has focused on isolating monomeric compounds in the metabolites of bacterial strains and screening endophytic fungi of Coptis chinensis that produce berberine. Further research on the diversity of endophytic fungi in medicinal plants and their metabolites is of great significance and value. Therefore, based on the geographical advantages of Sichuan Huanglian, this study explores the diversity of endophytic fungi in Sichuan Huanglian, further studies the antibacterial mechanism of their metabolites, and provides a basis for the application of endophytic fungal resources in Huanglian.

 

In this study, 14 endophytic fungi, including Paraboremia sp., were isolated from the rhizomes, stems, leaves, and fibrous roots of Coptis chinensis plants Ilyonectria sp.、Clonostachys sp.、Volutella sp.、Fusarium avenaceum、Cylidrocladiella sp.、Cercospora sp.、Dendryphion nanum、Phomatospora biseriata、Colletotrichum sp.、Didymellaceae sp.。 Except for the reported genera Ilyonectoria and Fusarium in the literature, the remaining 12 endophytic fungi have not been reported. Therefore, this study greatly enriches the species diversity of endophytic fungi in Coptis chinensis in Sichuan region and lays a good foundation for future research.
Huanglian, as a traditional Chinese medicine, has good antibacterial and anti-inflammatory effects, but there is little research in the field of endophytic bacteria. This study screened the inhibition of S Cop L01, an endophytic fungal strain of Coptis chinensis grown by Aureus, belongs to Colletotrichum sp. Comparing domestic and foreign literature, it is found that this type of bacteria is a common endophytic bacterium in plants, including Artemisia annua, Dendrobium officinale, Taxus chinensis, and other plants, all of which have been isolated. At the same time, there have been many studies on the antibacterial activity of the metabolites of this fungus. The metabolites of Colletotrichum sp., an endophytic fungus in Artemisia annua, have antibacterial effects on Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger; The methanol extract of Colletotrichum sp., an endophytic fungus in Huangjing, showed antibacterial activity against multidrug-resistant Staphylococcus aureus with a MIC value of 31 μ g/mL. In summary, the strain Cop L01 obtained in this study deserves further investigation. It is necessary to conduct further research on the composition of Cop L01 metabolites and the structure of related compounds. Literature has also reported endophytic fungi of Cop that produce berberine, which can further explore whether endophytic fungi of Cop can produce secondary metabolites that are the same or similar to those of the host, or the emergence of new active substances. Endophytic fungi are a great treasure trove of natural active substances, and researchers should comprehensively and deeply develop and utilize this resource.