IWASAKI Nozomu Kochi Univ. Usa Mar. Biol. Inst., Assitant, 海洋生物教育研究センター, 助手 (20193724)
OHNO Masao Kochi Univ. Usa Mar. Biol. Inst., Prof., 海洋生物教育研究センター, 教授 (10036543)
KOTSUKI Hiyoshizo Kochi Univ. Faculty of sci., Assoc. Prof., 理学部, 助教授 (80093954)
|Budget Amount *help
¥6,600,000 (Direct Cost: ¥6,600,000)
Fiscal Year 1990: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1989: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1988: ¥4,700,000 (Direct Cost: ¥4,700,000)
1. Collection and Screening
We collected fifty-one species of marine algae and seventy-nine species of sessile invertebrates from the coastal waters of southwestern Shikoku, and subjected the crude extracts obtained from them to screening for insect growth inhibitory activity against silkworm larvae and for lethality to brine-shrimp larvae. Of these extracts examined, those from twenty-seven species belonging to the Subclass Octocorallia exhibited significant activities against the test animals.
2. Isolation and Structural Determination
We investigated the biologically active constituents of five octocorals, Litophyton sp., Calicogorgia sp., Muricella sp., Ellisella SP., and Acalycigogia sp., to isolate thirty-three diterpenoids, two branched-chain lipids, three sphinganine derivatives, and five Secosterols. Their structures were established on the basis of spectroscopic and chemical evidence.
3. Biological Activities of Isolated Compounds
We evaluated biological activities of above compounds against silkworm and brine-shrimp larvae. Most of diterpenoids exhibited significant activities in both assays. Secosterols showed only lethality to brine-shrimp, while branched-chain lipids and sphinganine derivatives were all inactive in both assays. On the other hand, in order to elucidate the ecological role of these compounds in marine habitats, we also examined repelling and lethal activities against the muricid gastropod, Drupella fragum B., which has caused an environmental problem in the coastal waters of the Southwest of Japan by population explosions with widespread destruction of scleratinian corals. Many of diterpenoids, branched-chain lipids, and sphinganine derivatives were found to serve as defensive allomones.