Minor Sesquiterpenes with New Carbon Skeletons from the Brown Alga Dictyopteris divaricata

Abstract

Five minor sesquiterpenes (1-5) with two novel carbon skeletons, together with a minor new oplopane sesquiterpene (6), have been isolated from the brown alga Dictyopteris divaricata. By means of spectroscopic data including IR, HRMS, 1D and 2D NMR, and CD, their structures including absolute configurations were assigned as (+)-(1R,5S,6S,9R)-3-acetyl-1-hydroxy-6-isopropyl-9-methylbicyclo[4.3.0]non-3-ene (1), (+)-(1R,3S,4S,5R,6S,9R)-3-acetyl-1,4-dihydroxy-6-isopropyl-9-methylbicyclo[4.3.0]nonane (2), (+)-(1R,3R,4R,5R,6S,9R)-3-acetyl-1,4-dihydroxy-6-isopropyl-9-methylbicyclo[4.3.0]nonane (3), (+)-(1S,2R,6S,9R)-1-hydroxy-2-(1-hydroxyethyl)-6-isopropyl-9-methylbicyclo[4.3.0]non-4-en-3-one (4), (-)-(5S,6R,9S)-2-acetyl-5-hydroxy-6-isopropyl-9-methylbicyclo[4.3.0]non-1-en-3-one (5), and (-)-(1S,6S,9R)-4-acetyl-1-hydroxy-6-isopropyl-9-methylbicyclo[4.3.0]non-4-en-3-one (6). Biogenetically, the carbon skeletons of 1-6 may be derived from the co-occurring cadinane skeleton by different ring contraction rearrangements. Compounds 1-6 were inactive (IC(50) > 10 mug/mL) against several human cancer cell lines.

What are and where are the bioactive terpenoids metabolites from Dictyotaceae (Phaeophyceae)

“…Halogenated sesquiterpenes (whose main sources are the red algae) are reported in Padina antillarum (Parameswaran et al, 1994(Parameswaran et al, , 1996 and Dictyopteris divaricata , and sesquiterpenes without halogens in Dictyopteris divaricata (Song et al, 2005(Song et al, , 2006Qiao et al, 2009;Wen et al, 2009), D. undulata (Song et al, 2004a) and Taonia atomaria (De Rosa et al, 1994). For the latter two genera, 36 and six species are recognized, respectively, while for Padina 37 species are still valid.…”

Seaweeds as Source of New Bioactive Prototypes

“…These compounds have shown a moderate anticancer activity, with IC 50 values above 10 µ against several human cancer cell lines including lung adenocarcinoma (A549), stomach cancer (BGC-823), breast cancer (MCF-7), hepatocellular carcinoma (Bel7402), and colon cancer (HCT-8) cell lines [60]. Six other sesquiterpenes showed a similar IC 50 value against several human cancer cell lines [61].…”

Natural Sesquiterpenoids

“…182, 183 Another compound of this type 187 has been found in an extract from the brown alga Dictyopteris divaricata. 184 New helminthosporal analogues with plant growth regulatory properties have been synthesised. 185 …”

“…These compounds have two new different carbon frameworks, which may be derived from a cadinane. 184 The Formosan soft coral Clavularia inflata var. luzoniana 397 contains the sesquiterpenoid 498, which possesses a new ring system.…”