Chemical Defense Mechanisms and Ecological Implications of Indo-Pacific Holothurians

Abstract

Sea cucumbers are slow-moving organisms that use morphological, but also a diversecombination of chemical defenses to improve their overall fitness and chances of survival. Sincechemical defense compounds are also of great pharmaceutical interest, we pinpoint the importanceof biological screenings that are a relatively fast, informative and inexpensive way to identify themost bioactive organisms prior to further costly and elaborate pharmacological screenings. In thisstudy, we investigated the presence and absence of chemical defenses of 14 different sea cucumberspecies from three families (Holothuriidae, Stichopodidae and Synaptidae) against ecologicalfactors such as predation and pathogenic attacks. We used the different sea cucumber crudeextracts as well as purified fractions and pure saponin compounds in a portfolio of ecologicalactivity tests including fish feeding assays, cytotoxicity tests and antimicrobial assays againstenvironmental pathogenic and non-pathogenic bacteria. Furthermore, we quantified andcorrelated the concentrations of sea cucumber characteristic saponin compounds as effectivechemical defensive compounds in all 14 crude extracts by using the vanillin–sulfuric acid test. Theinitial results revealed that among all tested sea cucumber species that were defended against atleast one ecological threat (predation and/or bacterial attack), Bohadschia argus, Stichopuscholoronotus and Holothuria fuscopunctata were the three most promising bioactive sea cucumberspecies. Therefore, following further fractionation and purification attempts, we also testedsaponin-containing butanol fractions of the latter, as well as two purified saponin species from B.argus. We could demonstrate that both, the amount of saponin compounds and their structurelikely play a significant role in the chemical defense strategy of the sea cucumbers. Our studyconcludes that the chemical and morphological defense mechanisms (and combinations thereof)differ among the ecological strategies of the investigated holothurian species in order to increasetheir general fitness and level of survival. Finally, our observations and experiments on thechemical ecology of marine organisms can not only lead to a better understanding of their ecologyand environmental roles but also can help in the better selection of bioactiveorganisms/compounds for the discovery of novel, pharmacologically active secondary metabolitesin the near future.

Secondary Metabolites from Marine Sources with Potential Use as Leads for Anticancer Applications

“…In the last 5 years, several studies have been carried out with the aim of evaluating the bioactive properties of marine organisms. Several studies have tested the extracts and the isolated compounds from extracts of marine organisms for bioactivities [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ], of which the cytotoxic activity [ 27 , 30 , 32 , 33 , 35 , 36 , 37 , 38 , 40 , 41 , 44 , 45 , 46 , 47 , 48 ] stands out. However, only in some studies was it possible to isolate the compounds and test them for cytotoxic activity [ 32 , 33 , 35 , 36 , 37 , 38 , 40 , 41 ].…”

Triterpene Glycosides from the Far Eastern Sea Cucumber Thyonidium (=Duasmodactyla) kurilensis (Levin): The Structures, Cytotoxicities, and Biogenesis of Kurilosides A3, D1, G, H, I, I1, J, K, and K1

“…As a continuation of our investigation of glycoside composition of the sea cucumber Thyonidium (=Duasmodactuyla) kurilensis (Levin), we report herein the isolation and structure elucidation of nine glycosides, kurilosides A 3 (1), D 1 (2), G (3), H (4), I (5), I 1 (6), J (7), K (8), and K 1 (9) as well as two desulfated derivatives, DS-kuriloside L (10) and DS-kuriloside As a continuation of our investigation of glycoside composition of the sea cucumber Thyonidium (=Duasmodactuyla) kurilensis (Levin), we report herein the isolation and structure elucidation of nine glycosides, kurilosides A3 (1), D1 (2), G (3), H (4), I (5), I1 (6), J (7), K (8), and K1 (9) as well as two desulfated derivatives, DS-kuriloside L (10) and DS-kuriloside M (11). The animals were collected near Onekotan Island in the Sea of Okhotsk.…”

“…The investigations of the triterpene glycosides from different species of sea cucumbers have a range of goals. Among them are the drug discoveries based on the promising candidates, demonstrating the target bioactivity [ 1 , 2 , 3 , 4 , 5 , 6 ], the solving of some taxonomic problems of the class Holothuroidea based on the specificity of the glycosides having characteristic structural peculiarities for the certain systematic groups [ 7 , 8 , 9 , 10 ], the ascertaining of biologic and ecologic functions of these metabolites [ 11 , 12 , 13 , 14 , 15 ], and the discovery of novel compounds, especially minor ones, that can be the “hot metabolites” clarifying the biosynthetic pathways of triterpene glycosides [ 16 , 17 , 18 ].…”

Chemical cues for intraspecific chemical communication and interspecific interactions in aquatic environments: applications for fisheries and aquaculture

“…For example, effective antifoulants against barnacles and microfoulants (Oguri et al 2017) have been found in the red alga Laurencia sp. (Oguri et al 2017), tunicates (Levert et al 2020), the mollusk Phidiana militaris (Levert et al 2020), holothurians (Kamyab et al 2020), and sponges (Tintillier et al 2020). Antifoulants may improve the success of marine invasive tunicates (Utermann et al 2020;Nagai et al 2021).…”