Tatsuo Higa

Biological Activity and Chemistry of the Compound Ascidian Eusynstyela tincta

The extract of the compound ascidian Eusynstyela tincta, collected from Palk Bay and Gulf of Mannar, India was subjected through a battery of biological screens. The crude methanolic extract and subsequent fractions exhibited antibacterial, antifungal, cytotoxic and feeding deterrent activities. The extracts showed broad-spectrum antibiotic activity, and inhibited both bacterial and fungal pathogens. It also showed 100% cytotoxicity (25(μg/ml) against Dalton’s lymphoma and Ehrlich ascites tumour cells. A consistent feeding deterrent activity was established in both laboratory and field trials. It deterred the gold fish Carassius auratus. Among the extract/fractions assayed, methanol/ chloroform fraction had remarkable activity. The crude extract was separated through bioassay-guided fractionation and the active metabolite was identified as a pyridoacridine alkaloid, Kuanoniamine A. This study demonstrates that the ascidian metabolite, which exhibits antibiotic, cytotoxic and feeding deterrent activities, may play a role in the chemical defense mechanism.