Sesquiterpenoids and diterpenes with antimicrobial activity from Leptosphaeria sp. XL026, an endophytic fungus in Panax notoginseng

Two new sesquiterpenoids, leptosphins A (1) and B (2), and a new cyclopiane diterpene, leptosphin C (3), along with four known diterpenes (4-7) were isolated from the solid fermentation cultures of an endophytic fungus Leptosphaeria sp. XL026 isolated from the leaves of Panax notoginseng. Their structures were elucidated by extensive spectroscopic methods and single-crystal X-ray diffraction (data). Compound 1 represents the first sulfur-containing eremophilane sesquiterpene. Compounds 5 and 7 displayed medium antifungal activity against Rhizoctonia cerealis, as well as 6 against Verticillium dahliae Kleb with an MIC value of 12.5 μg/mL. Furthermore, compounds 2, 5, 6 and 7 showed medium antibacterial activity against Bacillus cereus with MIC values of 12.5-6.25 μg/mL, as well as 6 also against Pseudomonas aeruginosa with an MIC value of 12.5 μg/mL.