Malabaricane and Isomalabaricane Triterpenoids, Including Their Glycoconjugated Forms

In this review, we discuss structural diversity, taxonomic distribution, biological activities, biogenesis, and synthesis of a rare group of terpenoids, the so-called malabaricane and isomalabaricane triterpenoids, as well as some compounds derived from them. Representatives of these groups were found in some higher and lower terrestrial plants, as well as in some fungi, and in a relatively small group of marine sponges. The skeletal systems of malabaricanes and isomalabaricanes are similar to each other, but differ principally in the stereochemistry of their tricyclic core fragments, consisting of two six-membered and one five-membered rings. Evolution of these triterpenoids provides variety of rearranged, oxidized, and glycoconjugated products. These natural compounds have attracted a lot of attention for their biosynthetic origin and biological activity, especially for their extremely high cytotoxicity against tumor cells as well as promising neuroprotective properties in nanomolar concentrations

Oxysterols from a Marine Sponge <i>Inflatella</i> sp. and Their Action in 6-Hydroxydopamine-Induced Cell Model of Parkinson’s Disease

Four new oxysterols 1&#8315;4 along with previously known oxygenated sterols 5&#8315;14 were isolated from the sponge Inflatella sp., collected from the Sea of Okhotsk. Structures of 1&#8315;4 were elucidated by the detailed NMR spectroscopic and mass-spectrometric analyses as well as by comparison of the corresponding experimental data with those reported in literature. The influence of compounds 1&#8315;14 on the viability of neuronal Neuro2a cells treated by 6-hydroxydopamine and reactive oxygen species (ROS) formation in these cells was investigated

New Isomalabaricane-Derived Metabolites from a <i>Stelletta</i> sp. Marine Sponge

In continuation of our studies on a Vietnamese collection of a Stelletta sp., sponge we have isolated two new isomalabaricane triterpenoids, stellettins Q and R (1 and 2), and four new isomalabaricane-derived nor-terpenoids, stellettins S-V 3–6, along with previously known globostelletin N. Among them, compound 3 contains an acetylenic fragment, unprecedented in the isomalabaricane family and extremely rare in other marine sponge terpenoids. The structures and absolute configurations of all new compounds were established by extensive NMR, MS, and ECD analyses together with quantum-chemical modeling. Additionally, according to obtained new data we report the correction in stereochemistry of two asymmetric centers in the structures of two known isomalabaricanes, 15R,23S for globostelletin M and 15S,23R for globostelletin N

New Isomalabaricane-Derived Metabolites from a Stelletta sp. Marine Sponge

In continuation of our studies on a Vietnamese collection of a Stelletta sp., sponge we have isolated two new isomalabaricane triterpenoids, stellettins Q and R (1 and 2), and four new isomalabaricane-derived nor-terpenoids, stellettins S-V 3&ndash;6, along with previously known globostelletin N. Among them, compound 3 contains an acetylenic fragment, unprecedented in the isomalabaricane family and extremely rare in other marine sponge terpenoids. The structures and absolute configurations of all new compounds were established by extensive NMR, MS, and ECD analyses together with quantum-chemical modeling. Additionally, according to obtained new data we report the correction in stereochemistry of two asymmetric centers in the structures of two known isomalabaricanes, 15R,23S for globostelletin M and 15S,23R for globostelletin N

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

Investigation of the Vietnamese marine sponge Rhabdastrella globostellata led to the isolation of two new polar isomalabaricanes: rhabdastrellosides A (1) and B (2). Their structures and stereochemistry were elucidated with the application of 1D and 2D NMR, HRESIMS, and HRESIMS/MS methods, as well as chemical modifications and GC–MS analysis. Metabolites 1 and 2 are the first isomalabaricanes with non-oxidized cyclopentane ring in the tricyclic core system. Moreover, having a 3-O-disaccharide moiety in their structures, they increase a very rare group of isomalabaricane glycosides. We report here a weak cytotoxicity of 1 and 2 toward human neuroblastoma SH-SY5Y cells and normal rat H9c2 cardiomyocytes, as well as the cytoprotective activity of rhabdastrelloside B (2) at 1 µM evaluated using CoCl2-treated SH-SY5Y and H9c2 cells

Isolation, Structures, and Biological Activities of Triterpenoids from a <i>Penares</i> sp. Marine Sponge

Six new triterpenoids (<b>1</b>–<b>6</b>) and the previously known penasterone, acetylpenasterol, and ergosta-4,24(28)-dien-3-one were isolated from a <i>Penares</i> sp. sponge collected from Vietnamese waters. Structures of the obtained compounds were established by extensive 1D and 2D NMR spectroscopy and mass spectrometry. Configurations of the triterpene epoxy lactones (<b>1</b>–<b>4</b>) were determined on the basis of NOESY and CD data and calculation of spin coupling constants and confirmed by X-ray crystallographic analysis of compound <b>2</b>. The isolated triterpenoid <b>6</b> was cytotoxic against human leukemia HL-60 cells (IC₅₀ = 9.7 μM)

Lissodendoric Acids A and B, Manzamine-Related Alkaloids from the Far Eastern Sponge Lissodendoryx florida

The first representatives of a new group of manzamine-related alkaloids with a previously unknown skeletal systems, namely, lissodendoric acids A (<b>1</b>) and B (<b>2</b>), were isolated from the sponge Lissodendoryx florida collected from the Sea of Okhotsk. The structures and absolute configurations have been elucidated by extensive spectroscopic analysis together with chemical transformations and quantum-chemical modeling. The lissodendoric acids show a potent capability to decrease the production of reactive oxygen species in neuroblastoma Neuro 2a and somewhat increase the survival of these cells upon treatment with 6-hydroxydopamine (an <i>in vitro</i> antiparkinson biotest)