Good Practices in Sponge Natural Product Studies: Revising Vouchers with Isomalabaricane Triterpenes

Abstract

Species misidentification in the field of natural products is an acknowledged problem. These errors are especially widespread in sponge studies, albeit rarely assessed and documented. As a case study, we aim to revisit reports of isomalabaricane triterpenes, isolated from four demosponge genera: Jaspis, Geodia, Stelletta and Rhabdastrella. From a total of 44 articles (1981–2022), 27 unique vouchers were listed, 21 of which were accessed and re-examined here: 11 (52.4%) of these were misidentified. Overall, 65.9% of the studies published an incorrect species name: previously identified Jaspis and Stelletta species were all in fact Rhabdastrella globostellata. We conclude that isomalabaricane triterpenes were isolated from only two Rhabdastrella species and possibly one Geodia species. In addition to shedding a new light on the distribution of isomalabaricane triterpenes, this study is an opportunity to highlight the crucial importance of vouchers in natural product studies. Doing so, we discuss the impact of species misidentification and poor accessibility of vouchers in the field of sponge natural products. We advocate for stricter voucher guidelines in natural product journals and propose a common protocol of good practice, in the hope of reducing misidentifications in sponge studies, ensure reproducibility of studies, and facilitate follow-up work on the original material.

Unusually cyclized triterpenoids: occurrence, biosynthesis and chemical synthesis

“…However, taxonomic identication of these sponges remains questionable. 139,140 On the other hand, malabaricane triterpenoids were present in higher plants, fungi, ferns, and bottom sediments. 140 Moreover, iridals were found in the Iridaceae family, mainly in the genus Iris.…”

Marine natural products

“…The authors of the study recommend stricter guidelines for identi-cation of sponges and also for the storage of voucher specimens. 478 This journal is © The Royal Society of Chemistry 2024…”

Rhabdastrellosides A and B: Two New Isomalabaricane Glycosides from the Marine Sponge Rhabdastrella globostellata, and Their Cytotoxic and Cytoprotective Effects

“…Recently, the extensive re-examination of 21 sponge vouchers reported as sources of isomalabaricane triterpenes was provided by Cárdenas et al As a result, 11 sponge samples assigned previously as Jaspis sp., Jaspis stellifera, Stelletta sp., Stelletta tenuis, or Geodia globostellifera were found to be misidentified. According to the revision, isomalabaricane triterpenes were isolated only from samples of R. globostellata, one currently undescribed species of Rhabdastrella sp., and one putative species of Geodia [12,13].…”