Study on Secondary Metabolites of Colletotrichum sp. B-152, an Endophytic Fungus of the Sword leaved Dragon Blood Tree
Endophytes refer to a group of microorganisms that live in healthy plant tissues but do not cause host infections or diseases. They are widely present in healthy plant tissues and not only contain rich secondary metabolite synthesis gene clusters, but also produce various active ingredients. They can improve plant stress resistance such as salt tolerance, drought tolerance, cold tolerance, and insect resistance. Due to the diverse biological activities of endophytic fungi, Colletotrichum is considered a potential drug candidate. The genus Colletotrichum contains many plant endophytic fungi, and due to its rich biosynthetic gene cluster, Colletotrichum has become an important source of various metabolites, such as cyclic phosphopeptides, anthraquinone, isophthalic acid lactones, and pyranone. The diverse extracts and secondary metabolites of Colletotrichum have been reported to have antibacterial activity.
The research team found in the early stage that the endophytic fungus Colletotrichum sp. B-152 isolated from the leaf tissue of Dracaena Vand. ex L. and Dracaena cochinchinensis (Lour.) S. C. Chen in the Liliaceae family has broad-spectrum antibacterial activity. Therefore, the secondary metabolites were isolated and purified, and 18 pathogenic indicator bacteria were selected as targets for antibacterial activity testing of the obtained monomeric compounds, in order to discover compounds with potential antibacterial activity. This not only provides a reference for discovering new natural active compounds, but also has important significance for enriching the secondary metabolites and functional diversity of the Colletotrichum genus.

 

 

We isolated a total of 9 compounds from the secondary metabolites of the endophytic fungus Colletotrichum sp. B-152, which was isolated and preserved from the sword leaved dragon blood tree. Compounds 2-4, 6, 7, and 9 were isolated for the first time from a fungus of the genus Colletotrichum. 2-Hydroxy-4-methyl-1-phenyl-3-pentanone (1) was first reported as a natural product. From the results of antibacterial activity, compounds 5, 7, and 8 have the same structure as compounds in the same series, but exhibit different activities, and their structure-activity relationship needs further research and verification; Compound 2 has stronger antibacterial activity against Acinetobacter baumannii ATCC 19606 than compound 1, which may be related to the different substituents at position 3 in the structures of the two compounds. In addition, previous studies have shown that adenosine (4) has in vitro anti influenza virus (H1N1) activity; (22E, 24R) – ergosta-7, 22-diene-3 β, 5 α, 6 β – triol (5) exhibits strong inhibitory activity against gastric cancer SGC-7901 cells; The inhibitory activity of (4E, 8E) – N-D-2 ‘- hydroxypalmitoyl-1-O – β – D-glycocopyr-anosyl-9-methyl-4,8-sphingadienine (6) against herpes simplex virus (HSV-1) is 20 times that of the positive drug ribavirin, and the inhibitory activity against enterovirus 71 (EV71) is 5 times that of the positive drug ribavirin; Tuberosider (7) has strong inhibitory activity on the proliferation of human breast cancer cell MCF-7 and dog kidney cell MDCK; (22E, 24R) -5 α, 8 α – epidioxygeergosta-6,22-dien-3 β – ol (8) has a certain inhibitory effect on mouse lung adenocarcinoma cell line A-549. These studies indicate that compounds isolated from Colletotrichum fungus have good antibacterial, antiviral, and anti-tumor activities, providing new evidence for the discovery of novel antibacterial drugs and active natural products.