Comparative metabolomic analyses of Holothuria cinerascens and Pseudocnella sykion

Abstract

Sea cucumbers are soft-bodied marine invertebrates revered for their potent health benefits derived from biologically active molecules. However, research has primarily focused on commercially valuable species, such as Apostichopus japonicus, leading to their overexploitation as well as neglect of other species that may also contain valuable metabolites and nutritional value. This study presents the first untargeted metabolomic comparison of two southern African sea cucumber species, Holothuria cinerascens and Pseudocnella sykion, using proton nuclear magnetic resonance and ultra-performance liquid chromatography quadrupole time-of-flight high-resolution mass spectrometry. These species were selected due to their limited prior study and their overlapping habitats along the KwaZulu-Natal coastline. Despite their shared geographical locality, they exhibit distinct metabolic profiles. H. cinerascens displayed elevated levels of metabolites involved in osmoregulation (betaine), energy and amino acid metabolism (xylose, glucose, alanine, glutamate, glutamine, lysine and taurine) and defence metabolites, including the presence of several triterpene glycosides, whereas P. sykion notably contained rosmarinic acid and higher proline levels. These differences probably reflect genetic, ecological and reproductive variations between the species. Even though it provides insights into sea cucumber metabolism, this study also underscores the challenges in holothurian metabolomics, including the scarcity of holothurian-specific annotations in metabolite databases and the absence of these species in the Dictionary of Marine Natural Products. By establishing the baseline metabolic compositions of these understudied species, this work provides a foundation for targeted metabolomics to elucidate their metabolic pathways, discover novel bioactive compounds, expand aquaculture practices, foster economic opportunities and advance sustainable resource management and conservation efforts.

Significance:

This study presents the first metabolomic comparison of H. cinerascens and P. sykion from South Africa. Despite their geographic proximity, the species exhibit distinct metabolic profiles. H. cinerascens displayed greater metabolic diversity – including a higher potential for triterpene glycosides and osmolytes – suggesting increased environmental exposure and stress. Unidentified metabolites, particularly in P. sykion, hint at novel bioactive compounds. Overall, the study highlights gaps in holothurian-specific metabolomics and underscores the need for compound isolation, fragmentation and pathway analyses. These findings demonstrate the metabolic potential of lesser-known species and advocate for expanded research to support drug discovery, aquaculture and sustainable marine resource management.