Isao Kubo

Chemical ecology: studies from East Africa.

The International Centre of Insect Physiology and Ecology (ICIPE), in Nairobi, provides a laboratory at which a multinational group of scientists pursues interdisciplinary research. In collaboration with their colleagues in biology, ICIPE chemists have characterized the sex pheromones of the tick which serves as a vector of East Coast fever and have identified a termite queen-cell-building pheromone. The structure of many anthropod defensive chemicals have been determined; most interesting of these are the trinervitenes, structurally novel diterpenoids from nasute termites. Several highly active insect antifeedants were discovered using a simple bioassay to screen selected East African plants. These antifeedants may provide leads for the development of new insect-control techniques.

Insect antifeedant secoaromadendrane-type sesquiterpenes from Plagiochila species

Abstract The characteristic pungency of the liverworts Plagiochila species P. fruticosa, P. hattoriana, P. ovalifolia and P. yokogurensis is due to a new ent-secoaromadendrane-type sesquiterpene hemiacetal, plagiochiline A, which exhibits very strong antifeedant activity against the African army worm, Spodoptera exempta at 1–10ng/cm2. Two new secoaromadendranes, plagiochilide and furanoplagiochilal A, together with the previously known plagiochiline C were isolated from P. yokogurensis. Plagiochilal A, which may be a precursor of plagiochilide and its related hemiacetals, and a bitter principle, plagiochiline B were also isolated from P. hattoriana. P. ovalifolia contained plagiochilines A, B and C. From P. fruticosa, plagiochilide and plagiochilines A, B and C were isolated. The structures of the new secoaromadendrane-type sesquiterpenes were elucidated by extensive 1H NMR and 13CNMR studies.

Isolation, structure and synthesis of 4-hydroxyisoxazole (triumferol), a seed germination inhibitor from an african plant

Abstract The isolation, characterization and an efficient synthesis of 4-hydroxyisoxazole 1 , a plant growth regulator isolated from an African plant is reported. It is a new compound, which despite the simple structure, had eluded synthesis.

Some Terpenoid Insect Antifeedants from Tropical Plants

Abstract- A summarized account is given on the insect antifeedants of terpenoid nature which have been isolated from tropical plants is given. The armyworms Spodoptera exempta , S. littoralis and S. eridania , and the Mexican bean beetle Epilachna varivestis have been employed for the leaf-disk method of bioassay. The ten or so terpenoid antifeedants summarized here (published and unpublished data) exhibit activities other than insect antifeedant. The rationale for this result together with some of the difficulties which inherently accompany the search of bioactive compounds from natural sources are discussed.