Additional Sesterterpenes and a Nortriterpene Saponin from the Sponge Clathria gombawuiensis

Abstract

Three new terpene metabolites (1-3) were isolated from the marine sponge Clathria gombawuiensis collected from Korean waters. On the basis of the results of combined spectroscopic analyses, the structures of phorone B (1) and ansellone C (2) were determined to be the sesterterpenes of the phorone and ansellone classes, respectively, whereas the saponin gombaside A (3) was a nortriterpene sodium O-sulfonato-glucuronide of the rare 4,4,14-trimethylpregnane class. The absolute configuration of the glucuronate of 3 was assigned by an application of the phenylglycine methyl ester (PGME) method. The new compounds exhibited moderate cytotoxicity against A549 and K562 cell lines, and compound 3 showed antibacterial activity. The cytotoxicity of 1 may be related to the presence of a free phenolic -OH group, as the corresponding O-methoxy derivative 4 is inactive.

Marine natural products

“…674) were reported from ve different sponge genera, Carteriospongia, Hyattella, Ircinia, Phyllospongia and Spongia respectively. Other new sesterterpenoids were 1074 and 1075 (Clathria gombawuiensis) 675 and 1076 (Haliclona sp.) sourced from Korean collections.…”

“…680 While 1085 was toxic to RAW264.7 cells (IC 50 65 mM), both 1086 and 1087 were not, but instead were immunomodulatory inhibiting mRNA expression of IL-6 by $70% at 10 mM even though monanchosterols A and B only differ by a single acetylation. 681 A nortriterpenoid-saponin 1088, 675 686 while the absolute conguration of euryspongin A 1102 (Euryspongia sp.) was also determined using chiroptical techniques.…”

Triterpenoids

“…52 The saponin 177, with a new hexanorlanostane genin, has been reported from the sponge Clathria gombawuiensis. 53 Lanostane saponins with known genins include eryloside W from Dictyonella marsilii, 54 saponins of the sea cucumber Cladolabes schmeltzii has been assigned as R. 59 Other holostane saponins with known genins include cercodemasoides A-E from Cercodemas anceps, 60 cucumarioside E from Cucumaria japonica 61 and moebioside A from Holothuria moebii. 62 Reviews covering biological and taxonomic signicance of sea cucumber holostane saponins 63 and their antitumour, anti-inammatory and immunostimulatory properties 64 80 Two reviews of triterpenoids from Schizandra species have been published.…”

A biomimetic approach towards phorone sesterterpenoids

“…collected off the coast of Korea, and reported in 2012 by Nam, Kang and their co-workers. 1 More recently, the isolation of phorone B (2), which exhibits anti-cancer activity, was reported in 2015 by Woo et al 2 from the Korean marine sponge Clathria gombawuiensis. While isolated from two distinct genera of sponge, the phorones are likely derived from a common biogenesis related to that of a large family of bioactive sesterterpenoids: encompassing the phorbaketals (6), 3 alotaketals (7) 4 and ansellones (8, 9) 5 (Scheme 1) as well as the gombaspiroketals, 6 phorbasones 7 and isophorbasones 1 whose isolations have spawned multiple total synthesis efforts over recent years.…”