Spiroindimicins A-D: New Bisindole Alkaloids from a Deep-Sea-Derived Actinomycete

A PCR-based screening approach led to the identification of a deep-sea-derived Streptomyces sp. SCSIO 03032 capable of producing new bisindole alkaloids spiroindimicins A-D (1-4). Structural elucidation of these compounds revealed the presence of unusual [5,6] or [5,5] spiroring containing skeletons. Spiroindimicins B-D (2-4) with a [5,5] spiro-ring exhibited moderate cytotoxicities against several cancer cell lines.