Phorone A and Isophorbasone A, Sesterterpenoids Isolated from the Marine Sponge Phorbas sp.

Abstract

A chemical investigation of a Korean marine sponge, Phorbas sp., yielded unprecedented sesterterpenoids phorone A (1) and isophorbasone A (2) along with ansellone B (3) and phorbasone A acetate (4). Their complete structures were elucidated by the combination of spectroscopic data and chemical manipulation. Phorone A (1) and isophorbasone A (2) have the new "phorane"(5) and "isophorbasane"(6) sesterterpenoid carbon skeletons, respectively. Ansellone B (3) and phorbasone A acetate (4) exhibited potent inhibitory activity on nitric oxide production in RAW 264.7 LPS-activated mouse macrophage cells with IC(50) values of 4.5 and 2.8 μM, respectively.

Marine natural products

“…Compounds 857 and 858, described in the paper's supporting information, were low mM inhibitors of NO production in LPS-stimulated RAW 264.7 cells, while 855 and 856 are the rst examples of two new carbon skeletons. 719 Flabelliferins A 859 and B 860 came from Carteriospongia abellifera (Tutuba Is., Vanuatu). Both showed modest growth inhibition against human colon cancer cell lines, 720 The archetypical anti-inammatory scalarane sesterterpenoid scalaradial (Cacospongia mollior) 722 acted as a non-covalent binder in the active site of phospholipase A 2 and chelates Ca 2+ but did not covalently bind to the enzyme through dial reactivity.…”

Marine Low Molecular Weight Natural Products as Potential Cancer Preventive Compounds

“…In particular, ansellone B showed a favorable selectivity index (SI) of 3.8, which is indicative of its inducible isoform nitric oxide synthase (iNOS) inhibitory activity without significant cytotoxicity [99]. …”

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.…”