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

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 EC 50 value of 15.1 µg/mL, while compounds 5 - 7 showed certain ferric reducing ability.