Composition and biological activities of the aqueous extracts of three scleractinian corals from the Mexican Caribbean: Pseudodiploria strigosa, Porites astreoides and Siderastrea siderea

Abstract

BackgroundScleractinian corals (stony corals) are the most abundant reef-forming cnidarians found in coral reefs throughout the world. Despite their abundance and ecological importance, information about the diversity of their toxins and their biological activities is very scarce. In this study, the chemical composition and the biological activities of the aqueous extracts of Pseudodiploria strigosa, Porites astreoides and Siderastrea siderea, three scleractinian corals from the Mexican Caribbean, have been assessed for the first time.MethodsToxicity of the extracts was assessed in crickets; the presence of cytolysins was detected by the hemolysis assay; the vasoconstrictor activity was determined by the isolated rat aortic ring assay; the nociceptive activity was evaluated by the formalin test. The presence of phospholipases A2 (PLA2), serine proteases, and hyaluronidases was determined by enzymatic methods. Low-molecular-weight fractions were obtained by gel filtration chromatography and ultrafiltration.ResultsExtracts from the three species were toxic to crickets, induced hemolysis in human and rat erythrocytes, produced vasoconstriction on isolated rat aortic rings, and presented phospholipase A2 and serine-protease activity. Despite the fact that these corals are not considered to be harmless to humans, the extracts generated significant nociceptive responses. The matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry analysis of the low-molecular-weight fractions revealed the presence of peptides within a mass range of 3000 to 6000 Da. These fractions were toxic to crickets and two of them induced a transitory vasoconstrictor effect on isolated rat aortic rings.ConclusionThis study suggests that scleractinian corals produce low-molecular-weight peptides that are lethal to crickets and induce vasoconstriction.

Marine Natural Products from the Yucatan Peninsula

“…Four of them belong to the T-1 conotoxin family, (18V) sr5a (59), (18T) sr5a (60), "extended" (61), and "hydrophilic" (62), which were reported in 2009 [34], and they are very similar to the conotoxin sr5a (53). The other three, reported in 2010, were the known conotoxin sr11a (56) already reported in 2007 [31] and the new conotoxins, sr11b (63) and sr11c (64) [35] (Figure 9). Finally, Aguilar and collaborators reported in 2009 the isolation of a new peptide, pal9a (65) (3678.84 Da) with 34 amino acids, including six cysteine residues, from a third mollusk, Polystira albida, collected in Campeche state.…”

“…Out of the 66 marine natural products identified, 26 correspond to structures that were not previously reported. These 26 new chemical entities correspond to three aliphatic polyketides (1-3), one glycolipid (7), two diterpenes (15,16), two steroids (24,25), one triterpenoid saponin (40), and 17 conotoxins (49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62)(63)(64)(65). Figure 15 displays the overall biogenetic distribution of the reported compounds.…”

Coral Venom Toxins

“…Although the compounds responsible for the bioactivity were not characterized in this study, a recent study on the analysis of extracts from the nematocysts of three stony corals (Scleractinia corals), Pseudodiploria strigosa, Porites astreoides, and Siderastrea sidereal indicated the presence of a range of toxins and provided insight into the chemical composition. Extracts from all three corals were lethal to crickets, had haemolytic and nociceptive activity to varying extents, and exhibited PLA 2 and serine protease activities (Garcia-Arredondo et al, 2016). Interestingly, although these corals are not considered harmful to humans, the activity of these extracts is consistent with the physiological effects caused in humans by some hydroids, such as Millepora alcicornis and Millepora complanate, where the toxins work as lysins on erythrocytes (Garcia-Arredondo et al, 2016).…”

“…Their venom can be extremely potent and act, not only on small marine prey organisms, but can also have severe physiological effects on humans (Tibballs, 2006;Tibballs et al, 2011;Remigante et al, 2018). Although not as harmful as some jellyfish, other cnidarians, such as select sea anemones can elicit a stinging sensation in humans when the nematocytes in the tentacles are stimulated (Lubbock et al, 1981;Garcia-Arredondo et al, 2016). Several sea anemone toxins have been well-characterized, including an analog of a ShK toxin from Stichodactyla helianthus, which has entered Phase 2 trials for autoimmune diseases (Pennington et al, 2009;Chi et al, 2012;Prentis et al, 2018).…”

“…For example, metabolites from the gorgonian coral Erythropodium caribaeorum have been shown to act as a deterrent against reef fishes predating on the coral (Fenical and Pawlik, 1991). However, more recent studies have characterized venom derived coral toxins, with potential in the field of drug development (Radwan et al, 2002;Frazao et al, 2012;Rodriguez et al, 2012;Garcia-Arredondo et al, 2016). There is significant scope for future studies aimed at characterizing coral toxins, and in this mini review we highlight some of the structural and functional diversity that has already been uncovered.…”