Abstract:
Over the course of this study, various species of Tongan marine sponges were investigated
using an NMR-based screening method and has resulted in the discovery of three new
sesterterpenes and 11 known compounds.
Examination of the sponge Fascaplysinopsis sp. resulted in the isolation of two novel
sesterterpenes, isoluffariellolide (46) and 1-O-methylisoluffariellolide (47). Compounds
46 and 47 share the same backbone pattern as the known luffariellolide (45) and 25-Omethylluffariellolide
(107) respectively, and differ only in the substitution pattern of the
butenolide rings. Isoluffariellolide (46) was found to be approximately six times less
cytotoxic than 1-O-methylisoluffariellolide (47). Interestingly, these results suggested
that the 1-O-methyl group in compound 47 plays an important role in the cytotoxicity of
the compound.
Secothorectolide (49), a new ring-opened and geometric isomer of the known compound
thorectolide (48), was obtained from a sponge of the order Dictyoceratida. This
ring closure and opening relationship was also observed between manoalide (109) and
secomanoalide (110), as well as luffariellins A (141) and B (142). Despite the different
carbon skeleton, the functional groups in 141 and 142 are similar with those in 109 and
110, respectively, and not surprisingly the biological properties are almost identical. The
biological activities of compounds 48 and 49 were almost the same, which would give an
insight into the structure-activity relationship (SAR) between these types of compounds.
