Chemical studies on Antarctic nudibranch molluscs

Abstract

Two opisthobranchs, Austrodoris kerguelenensis and Bathydoris hodgsoni, collected from Antarctica in the framework of Spanish and German expeditions, were chemically investigated in order to identify the skin secondary metabolites, probably involved in the chemical defense of these molluscs. Some new terpenoid molecules were isolated from the mantle and their structures were established by spectroscopic methods, mainly by Nuclear Magnetic Resonance techniques. The absolute configuration at C-2' of the glyceryl moiety of diterpenoid 1,3-glyceryl esters from A. kerguelenensis was determined to be R by applying the modified Mosher method. Surprisingly, this configuration is the opposite of that of all marine terpenoid diacylglycerols so far reported. Other results described here were derived from synthetic studies on optically active terpenoid diacylglycerols, structurally related to the compounds isolated from A. kerguelenensis.

Chemical Interactions in Antarctic Marine Benthic Ecosystems

“…This is demonstrated by the fact that more than 50% of the studied species of the main taxonomical groups exhibited significant deterrent activities. In agreement with these findings, previous experiments already demonstrated strong feeding deterrency towards this sea star in the opisthobrach molluscs Austrodoris kerguelenensis (Gavagnin et al, 2000;Iken et al, 2002) and Bathydoris hodgsoni (Avila et al, 2000). In the present survey, the tunicates exhibited the highest repellent activity (73%).…”

Bioactive Compounds from Marine Heterobranchs

“…This slug possesses many other molecules that may not be involved in defense against predators, including additional diterpene glycerides with different skeletons, such as ent -labdane, labdane, halimane, clerodane, and isocopalane diterpenes, as well as norsesquiterpenes [ 18 , 58 , 59 , 62 , 63 , 64 , 65 , 66 , 67 ]. Cryptic speciation has been reported in D. kerguelenensis, and this could be behind their chemical variability, even at the intrapopulation level, as well as perhaps the presence of different terpene synthase variants involved in their de novo biosynthesis [ 61 , 67 , 68 , 69 , 70 ]. Since these compounds occur in complex mixtures in the slug, it seems difficult to trace the bioactivity to the individual compounds.…”

The chemistry and chemical ecology of nudibranchs

“…184 Not surprisingly, as for Archidoris, it is thought likely that the above compounds are biosynthesised de novo by the nudibranch. 191,192 The verrucosins are also diterpenoid acid glycerides obtained from Doris verrucosa, 193,194 and in addition to icthyotoxicity, verrucosins A and B (51 and 52) were shown to be potent activators of protein kinase C and to promote tentacle regeneration in the freshwater hydrozoan Hydra vulgaris. 195 Biosynthetic feeding experiments with 14 C labelled mevalonic acid and glycerol resulted in poor incorporation into the verrucosins so de novo biosynthesis was not proven but good incorporation into sterols did establish that the mevalonate pathway was operative in the nudibranch.…”