Abstract
Discovering new secondary metabolites is an especially urgent task due to
the rapid spread of bacterial resistance and the emergence of multi-resistant pathogenic
strains of infectious diseases. Octocorals (soft corals and gorgonians) are a highly
diverse group of marine organisms, which are known to contain a rich variety of rare
and unusual secondary metabolites. These substances show not only great significance
in chemical ecology but also various biological activities. Despite the intense interest in
the isolation of novel compounds from octocorals, little is known about within and
between-habitat variability in the levels and types of compounds in these species.
Marine organisms living in extreme environments evolve unique strategies by
biosynthesizing more diverse compounds than their counterparts living in moderate
environments. Coral reefs of the Gulf of Mannar in India have a more moderate
environment (with a sedimentation rate of 12.31 mg.cm-2day-1); whereas the Gulf of
Kachchh is a marginal reef experiencing arid climate and heavy sedimentation rate
(upto119.60 mg.cm-2d
-1). In a preliminary cytotoxicity assay, carried out to evaluate the
bioactivity of selected soft corals from the Gulf of Mannar and the Gulf of Kachchh,
the highest cytotoxicity was exhibited by Mannar soft corals, Sinularia leptoclados
(LC50=25.15μg/ml) followed by Sarcophyton ehrenbergi (LC50=43.76μg/ml). Whereas
soft corals collected from the Gulf of Kachchh exhibited higher cytotoxicity than the
Mannar samples (Si. leptoclados (LC50=19.24μg/ml) followed by Si. polydactyla
(LC50=24.50μg/ml). Extreme physico-chemical and biological conditions in the
Kachchh are the drive for the production of variant molecules with specific adaptations.
Hence, soft corals inhabited in extreme waters may yield more effective compounds that may potentially be useful in drug development for existing and emerging human
ailments.