β-Carboline Alkaloids from a Korean Tunicate Eudistoma sp.

Seven new β-carboline-based metabolites, designated as eudistomins Y₁−Y₇ (1−7), were isolated from a tunicate of the genus Eudistoma collected near Tong-Yeong City, South Sea, Korea. These new metabolites differ from previously isolated marine metabolites due to the presence of a benzoyl group attached to the β-carboline nucleus at C-1. Eudistomins Y₁−Y₇ were evaluated for their antibacterial activity, and eudistomin Y₆ exhibited moderate antibacterial activity against Gram-positive bacteria Staphylococcus epidermis and Bacillus subtilis without cytotoxicity in the MTT assay at 100 µM.