As part of systematic investigation of marine natural products isolated from sea animals, study on primary and secondary metabolites of Ligia exotica and sea pen have been carried out. The Ligia exotica collected in Busan area (September, 1988, KOREA) was homogenized with distilled water, filtered with membrane filter (denature process, mol. wt cut off 10000) and then dialyzed using cellulous membrane tube (mol. wt cut off 3500). The sea pen (Pennatura Sp.) collected in Thailand (dried soaking in $H_2O$, 1988) was dialyzed using cellulous membrane tube (mol. wt cut off, 3500). Water extracts of Ligia exotica and sea pen were liophilized to give the pale yellow sticky solid, which were chromatographed on gel column and low pressure preparative LC (Bio Gel P2). Each fractions of gel column (Bio Gel P2 and Sephadex G10 column) were separated by recycle preparative HPLC (GS 320 and ODS column). Among the isolated constituents, betaine, inosine, and many free amino acids (Phe, Tyr, Trp, Ala, Pro, Val, Ile, and Leu) were elucidated by spectral data. Water extracts of Ligia exotica and sea pen show strong histamine inhibitory effects (Ligia exotica: 76%, sea pen: 79%). Especially, one fraction of Ligia exotica shows very strong histamine inhibitory effect (94%).
Furthermore, other constituents which show biological activity are being further purified for their structural elucidation.