Altenuene is a mycotoxin, it frequently occurs in food and feed items infested by fungi of the genus Alternaria. Altenuene demonstrates moderate activity against Staphylococcus aureus. Altenuene also exhibits cytotoxic activity against lung cancer cell li

METHODS AND RESULTS:Two new polyketides, 7-hydroxy-3, 5-dimethyl-isochromen-1-one (1) and 6-hydroxy-8-methoxy-3a-methyl-3a,9b-dihydro-3H-furo[3,2-c]isochromene-2,5-dione (2), along with eleven known compounds, 5'-methoxy-6-methyl-biphenyl-3,4,3'-triol (3), 7-hydroxy-3-(2-hydroxy-propyl)-5-methyl-isochromen-1-one (4), rubralactone (5), isoAltenuene (6), Altenuene (7), dihydroAltenuenes A (8), altenusin (9), alterlactone (10), 6-O-methylnorlichexanthone (11), norlichexanthone (12), and griseoxanthone C (13) were isolated from the culture of the endolichenic fungus Ulocladium sp. Compound 2 was obtained as a racemate with an unprecedented chemical skeleton. The NMR data assignments for 3 and 4 were achieved for the first time. Compounds 1-13 were screened for their antimicrobial and radical scavenging activities. CONCLUSIONS: Compound 1 showed some antifungal activity against Candida albicans SC 5314 with IC(50) of 97.93 ± 1.12 μM. Compounds 11-13 showed strong activity against Bacillus subtilis with IC(50) in the range of 1-5 μM. Compound 12 significantly inhibited the growth of methicillin-resistant Staphylococcus aureus with IC(50) of 20.95 ± 1.56 μM. Compounds 9 and 10 showed strong radical scavenging activity in comparison with vitamin C. The plausible biosynthetic pathways for compounds 1, 2, and 4-8 were discussed.