Isolation of Chamigrene Sesquiterpenes and Absolute Configuration of Isoobtusadiene from the Brittle Star Ophionereis reticulata

Abstract

The chemical study of the Brazilian brittle star Ophionereis reticulata led to the isolation of three chamigrene sesquiterpenes, including the partially characterized isoobtusadiene (1), its unreported acetyl derivative (2), and the known (+)-elatol (3). The complete elucidation of the structures 1 and 2 was accomplished by 1D and 2D NMR spectroscopy. The first assignment of the absolute configuration of the isoobtusadiene skeleton is suggested as 6S,9R,10S on the basis of the NMR analysis of the Mosher's ester derivatives of 1 and the ECD study of the acetyl derivative 2. Chamigrenes are typical constituents of Laurencia red algae. O. reticulata is a predator with a preference for algae. Thus, the origin of these metabolites can be likely ascribed to diet.

Antioxidant and anticholinesterase properties of Echinometra mathaei and Ophiocoma erinaceus venoms from the Persian Gulf

“…In current study, GC-MS analysis of the BS, SSU, GSU and CSU samples showed 25, 12, 23, and 21 compounds including pyridines, piperidines, indole alkaloids, monoterpenes, xanthophylls, esters, sterols, alkanes, amides, carbohydrates, etc. These results in accordance with other studies focused on bioactivity of compounds derived from brittle stars and sea urchins (Nuzzo et al, 2017;Francis and Chakraborty, 2020a;Francis and Chakraborty, 2020b;Strobykina et al, 2020).…”

Marine natural products

“…Chamigrene sesquiterpenes isoobtusadiene 1455 and its acetate 1456 were isolated from the brittle star Ophionereis reticulata. 692 This compound class is typically reported from red algae, suggesting a dietary source for the brittle star. Phenolic sulfate monomers 1457, 1458 and dimers 1459, 1460, from the crinoid Alloeocomatella polycladia exhibited weak (former two) to moderate (latter two) inhibition of HCV NS3 helicase.…”

Newly discovered naturally occurring organohalogens

“…A brittle star, Ophionereis reticulata, from the coast of Brazil contains two known chamigrene sesquiterpenes in addition to the novel acetyl isoobtusadiene (139). 63 The known metabolites found in this animal are elatol and isoobtusadiene, which are common in Laurencia red algae, suggesting a dietary origin for these compounds. The halogenated diterpene dolabellol A (140) was characterized from the opisthobranch Dolabella auricularia found living off the Japanese coast (Figure 28).…”