ARTICLE pubs.acs.org/jnp

Theactinomycetes are a prolific source of structurally new andbiologically active metabolites and are responsible for pro-ducing over 45 % of all known microbial natural products.1 Most research on actinomycetes has been carried out with terrestrial species.2,3 However, the discovery of new lead compounds from common soil-derived actinomycetes has declined in the past two decades.4 Examining the natural product profiles of the under-exploited marine-derived actinomycetes has become a research hot spot in drug discovery. To date, nearly 400 new compounds with cytotoxicity and antimicrobial activity have been isolated from marine actinomycetes.58 As part of our ongoing research on new antitumor compounds from marine-derived actinomy-cetes, strain WH1-2216-6, identified as Actinoalloteichus cyano-griseus, was isolated from marine sediments and was found to exhibit significant cytotoxic effects on the K562 cell line. A series of metabolites contained in the extract of strain WH1-2216-