Chromone and isocoumarin derivatives from the endophytic fungus Xylomelasma sp. Samif07, and their antibacterial and antioxidant activities

Abstract

Five chromone derivatives, including 2,6-dimethyl-5-methoxyl-7-hydroxylchromone (1), 6-hydroxymethyleugenin (2), 6-methoxymethyleugenin (3), chaetoquadrin D (4), and isoeugenitol (5), and three isocoumarin congeners, namely diaporthin (6), 8-hydroxy-6-methoxy-3-methylisocoumarin (7), and 6-methoxymellein (8), were isolated from the culture of the endophytic fungus Xylomelasma sp. Samif07 derived from the medicinal plant Salvia miltiorrhiza Bunge. Among them, compound 1 was a new natural product. Their structures were determined by spectroscopic methods and comparison with the literature. The isolated compounds were evaluated for their antibacterial and antioxidant activities. Compound 5 showed notable antitubercular activity against Mycobacterium tuberculosis with MIC value of 10.31 µg/mL, while compounds 1–3, and 5–7 displayed inhibitory activities against the other bacteria with MIC range of 25 ∼ 100 µg/mL. Meanwhile, compound 6 showed potent hydroxyl radical-scavenging activity with EC₅₀ value of 15.1 µg/mL, while compounds 5–7 showed certain ferric reducing ability.

Graphical Abstract

Keywords:

• Endophytic fungus
• Xylomelasma sp. Samif07
• chromone
• isocoumarin
• antibacterial activity
• antioxidant activity

Acknowledgements

D. Lai was acknowledged to the StayConnected@HHU program for funding a research visit to Heinrich Heine University Düsseldorf.

Disclosure statement

All the authors declare no conflict of interest.

Funding

This work was partially supported by the National Key R&D Program of China (grant number 2017YFD0201105).