ABSTRACT
Many kinds of living creatures, of which there are more than 30 phyla and 500,000
species, exist in the oceans, which cover almost two-thirds of the Earth’s surface (Nien-
huis, 1981). Sea water is a unique environment, therefore, it may be expected that many
compounds with novel structures and differing bioactivities to those from terrestrial
environments may be found among marine metabolites. Nevertheless, marine organ-
isms did not attract chemists’ and ecologists’ attentions for a long time, probably
because little was known about their ecology.
