Mebamamide C, A Deoxy Analogue of Mebamamides in Bryopsis Marine Green Alga and Two Elysia Sacoglossan Mollusks

Kahalalides, originally isolated from the sacoglossan mollusk Elysia rufescens, have been found in various Elysia species and Bryopsis sp., with over twenty variants identified to date. These compounds are biosynthesized by Candidatus Endobryopsis kahalalidefaciens within Bryopsis species. In this study, we report the isolation and structural determination of a new cyclic depsipeptide, mebamamide C (1), from Bryopsis sp. The planar structure was determined by spectroscopic data analyses, and the absolute configurations were determined using Marfey's method and modified Mosher's method. Additionally, our study explores the chemical relationship between Bryopsis algae and Elysia mollusks. The individual chemical profiles of these marine organisms highlight a fascinating aspect of marine chemical ecology. The distinct, species-specific chemical profiles observed in Elysia species imply the possibility of a symbiotic relationship with the kahalalide-producing bacteria.