The secondary metabolites from halophilic actinomycetes from a solar saltern in Korea

Halophilic actinomycetes from saline environments are distinct from their terrestrial counterparts in terms of their physiology and secondary metabolites. Since the discovery of a novel anticancer drug candidate, salinosporamide A, from an obligate marine actinomycete, studies of halophilic actinomycete-derived secondary metabolites have demonstrated the chemical potential of actinomycetes from saline environments. Salterns may be an extreme representative of saline environments, which possibly harbor halophilic actinomycetes with chemical potential. We selectively isolated actinomycete strains from salterns and investigated their bioactive compounds. During our chemical studies, salternamides A-D (1-4), the first secondary metabolites from saltern-derived actinomycetes, were discovered from a halophilic Streptomyces strain (#HK10) isolated from a saltern on Shinui Island in the Republic of Korea. Salternamide A (1), which is the first chlorinated compound in the manumycin family, exhibited potent cytotoxicity against a human colon cancer cell line (HCT116) and a gastric cancer cell line (SNU638) with submicromolar IC50 values. Moreover, xiamycins C-E (5-7), new indolosequiterpenoids, were identified from another Streptomyces sp. strain (#HK18) isolated from a topsoil sample of the saltern. Xiamycins C-E showed potent effects against porcine epidemic diarrhea virus infection via inhibiting viral replication.