Tivity with the pairs of compounds (Table 1) colochiroside B2 (38) (Figure 7) and magnumoside B1 (8), also as colochiroside C (36) and magnumoside C3 (14), and differing by the aglycones nuclei (holostane and non-holostane, correspondingly), showed that compounds 36 and 38, which contained the holostane aglycones, had been much more active, and that is constant together with the earlier conclusions.Figure 7. Structure of colochiroside B2 (38) from Colochirus robustus.On top of that, the glycosides of the sea cucumber, Cucumaria fallax [42], didn’t show any activity resulting from containing unusual hexa-nor-lanostane aglycones with an eight(9)-double bond and with no a lactone. The only glycoside from this series, cucumarioside A3 -2 (39) (Figure eight), that was moderately Nimbolide Purity & Documentation hemolytic (Table 1) was characterized by hexa-nor-lanostane aglycone, but, as standard for the glycosides of sea cucumbers, having a 7(eight)-double bond and 9-H configuration, which demonstrates the significance of these structural components for the membranotropic action on the glycosides.Mar. Drugs 2021, 19,8 ofFigure eight. Structure of cucumarioside A3 -2 from Cucumaria fallax.The influence of your side chain length and character of a lactone (18(20)- or 18(16)-) is nicely illustrated by the comparative analysis of your hemolytic activity of your series of glycosides from E. fraudatrix (cucumariosides A1 (40) and A10 (41) [28,29]; cucumariosides I1 (42) and I4 (43) [43]) (Figure 9), which indicates that the presence of a normal side chain is essential for the higher membranolytic effect on the glycoside.Figure 9. Structures on the glycosides 403 from Eupentacta fraudatrix.Unexpectedly high hemolytic activity was displayed by cucumarioside A8 (44) from E. fraudatrix [29] (Figure 10) with special non-holostane Thromboxane B2 Purity & Documentation aglycone and without lactone but with hydroxy-groups at C-18 and C-20, which could be thought of as a biosynthetic precursor in the holostane aglycones. Its sturdy membranolytic action (Table 1) might be explained by the formation of an intramolecular hydrogen bond involving the atoms of aglycone hydroxyls resulting in the spatial structure of your aglycone becoming comparable to that of holostane-type aglycones. Noticeably, it is actually of unique interest to check this problem by in silico calculations to clarify the molecular mechanism of membranotropic action of 44.Figure 10. Structure of cucumarioside A8 (44) from Eupentacta fraudatrix.2.1.four. The Influence of Hydroxyl Groups inside the Aglycones Side Chain to Hemolytic Activity of the Glycosides A powerful activity-decreasing effect in the hydroxyl groups inside the aglycone side chains was revealed for the initial time when the bioactivity in the glycosides from E. fraudatrix was studied [279,43]. In reality, cucumariosides A7 (45), A9 (46), A11 (47), and A14 (48), as well as I3 (49), were not active against erythrocytes (Table 1) (Figure 11).Mar. Drugs 2021, 19,9 ofFigure 11. Structures on the glycosides 459 from Eupentacta fraudatrix and 50 from Colochirus robustus.On the other hand, colochirosides B1 (50) (Figure 11) and B2 (38) from C. robustus [24], with all the same aglycones as cucumariosides A7 (45) and A11 (47), correspondingly, but differing by the third (Xylose) and terminal monosaccharide residues (3-O-MeGlc) and the presence of sulfate group at C-4 Xyl1, demonstrated moderate hemolytic activity (Table 1). The activity of typicoside C1 (51) from A. typica [23] as well as cladolosides D2 (52) and K2 (53) from C. schmeltzii [40,41], with a 22-OH group in the holostane aglycones, was.