Isolation of 22-methylenecholesterol. Further evidence for direct bioalkylation of 22-dehydrocholesterol

Halipanasterol, a New Sterol Isolated From the Marine Sponge Halichondria panicea

A new sterol (1) and 8 known (2-9) compounds were isolated from the methanol extract of the Vietnamese marine sponge Halichondria panicea (Pallas, 1766) by various chromatographic methods. Their chemical structures were determined as 5 α,6 α-epoxy-(22 E)-ergosta-3 β,7 α-diol-8,22,25-triene (1), (22 E)-ergosta-7,22,25-triene-3 β,5 α,6 β-triol (2), 3 β-hydroxycholest-5ene-7-one (3), cholesterol sulfate (4), 3-formamidotheonellin (5), para-hydroxybenzylideneacetone (6), indole-3-carbaldehyde (7), thymidine (8), and adenosine (9) by using a combination of HR-ESI-MS, 1D and 2D NMR spectral data, as well as by comparison with the previous literature. This is the first report of these compounds from H panicea. Compounds 1 and 2 exhibited cytotoxic effects on Hep-G2, SK-Mel-2, LU-1, and MCF-7 cell lines with IC50 values of 9.27 ± 1.25, 11.34 ± 1.18, 15.45 ± 1.47, and 10.85 ± 1.19 µM (for 1), and 6.45 ± 0.77, 9.74 ± 1.03, 7.08 ± 0.64, 5.61 ± 0.39 µM (for 2), compared to the positive control compound, ellipticine, 1.60 ± 0.37, 2.53 ± 0.51, 1.82 ± 0.20, and 2.17 ± 0.66 µM, respectively.

"Dinoflagellate Sterols" in marine diatoms

Sterol compositions for three diatom species, recently shown to contain sterols with side chains typically found in dinoflagellates, were determined by HPLC and ¹H NMR spectroscopic analyses. The centric diatom Triceratium dubium (=Biddulphia sp., CCMP 147) contained the highest percentage of 23-methylated sterols (37.2% (24R)-23-methylergosta-5,22-dienol), whereas the pennate diatom Delphineis sp. (CCMP 1095) contained the cyclopropyl sterol gorgosterol, as well as the 27-norsterol occelasterol. The sterol composition of Ditylum brightwellii (CCMP 358) was the most complex, containing Δ⁰- and Δ⁷-sterols, in addition to the predominant Δ⁵-sterols. A pair of previously unknown sterols, stigmasta-5,24,28-trienol and stigmasta-24,28-dienol, were detected in D. brightwellii and their structures were determined by NMR spectroscopic analysis and by synthesis of the former sterol from saringosterol. Also detected in D. brightwellii was the previously unknown 23-methylcholesta-7,22-dienol.