Okichromanone, a new antiviral chromanone from a marine-derived Microbispora.

Okichromanone (1), a new chromanone, was isolated from the culture extract of a sponge-derived actinomycete Microbispora, along with known 1-hydroxyphenazine (2). Compound 1 was elucidated to exist as a mixture of two isomeric structures (1a and 1b) at a ratio of nearly 3:2. Compounds 1 and 2 showed anti HSV-I activity with IC 50 values 40 and 86 μM, respectively, and anti HSV-II activity with IC 50 values 59 and 123 μM, respectively.