Chemical defenses of the tropical marine seaweed Canistrocarpus cervicornis against herbivory by sea urchin

Abstract

This paper reports on the defensive chemical properties of the marine tropical brown seaweed Canistrocarpus cervicornis against herbivory. A natural concentration of dichloromethane crude extract (DCE) obtained from this seaweed significantly inhibited feeding by the sea urchin Lytechinus variegatus. The major metabolite isolated from this active DCE extract was identified as the (4R,7R,14S)-4α,7α-diacetoxy-14-hydroxydolast-1(15),8-diene that strongly inhibited feeding by the same sea urchin. This result suggests that the dolastane diterpenes class may constitute the defensive system of C. cervicornis against herbivory, and probably also of that of other brown seaweeds endowed with a biosynthetic pathway capable of producing compounds of the dolastane-type, a typical skeleton found in Dyctioteae species worldwide. This is the first report showing this compound-type (dolastane diterpenes) as a chemical defense against herbivory in marine seaweeds. This study constitutes an additional report broadening the known spectrum of action and roles of secondary metabolites of the C. cervicornis and Dyctioteae species.Este artigo demonstra a química defensiva anti-herbivoria da macroalga parda marinha Canistrocarpus cervicornis. Em sua concentração natural, o extrato bruto em diclorometano (DCE) inibiu significativamente o consumo alimentar do ouriço-do-mar Lytechinus variegatus. Deste extrato em DCE foi isolado o metabólito majoritário identificado como o diterpeno (4R,7R,14S)-4α,7α-diacetoxi-14-hidroxidolasta-1(15),8-dieno. Esses resultados comprovam que diterpenos da classe dolastano podem compor o sistema defensivo anti-herbivoria de C. cervircornis e, supostamente, o de outras algas pardas capazes de produzi-los, uma vez que são composto típicos encontrados em esqueletos de Dyctiotas em todo o mundo. Este é o primeiro estudo demonstrando a ação anti-herbivoria desta classe de metabolitos (diterpenos dolastanos) em macroalgas marinhas. Tais informações ampliam o conhecimento sobre o papel desses metabolitos especiais em C. cervicornis e de espécies de Dyctiotae.

Keywords

• Canistrocarpus cervicornis
• Defesas químicas
• Dolastanos
• Diterpenos
• Canistrocarpus cervicornis
• Chemical defenses
• Dolastanes
• Diterpenes