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Six new tetraprenylated alkaloids, designated as malonganenones L–Q (1–6), were isolated from the gorgonian Echinogorgia pseudossapo, collected in Daya Bay of Guangdong Province, China. The structures of 1–6 featuring a methyl group at N-3 and a tetraprenyl chain at N-7 in the hypoxanthine core were established by extensive spectroscopic analyses. Compounds 1–6 were tested for their inhibitory activity against the phosphodiesterases (PDEs)-4D, 5A, and 9A, and compounds 1 and 6 exhibited moderate inhibitory activity against PDE4D with IC50 values of 8.5 and 20.3 µM, respectively.

[structure: see text] Two unprecedented C,C-linked dimeric indolizidine alkaloids, flueggenines A (1) and B (2), as well as their biosynthetic precursor (-)-norsecurinine, were isolated from the roots of Flueggea virosa. Their structures and absolute configurations were elucidated by spectroscopic methods, especially 2D NMR and CD spectral analyses, and supported by their unique biosynthetic pathway as proposed. Both 1 and 2 were tested against two tumor cell lines, and alkaloid 1 showed weak activity against the P-388 cell line.

Five purine and carboline alkaloids were isolated from the methanol extract of the ascidian Symplegma oceania. Classic chromatographies including preparative HPLC were used for isolation and purification of the compounds. The structures were established as 6-methoxy-7-methyl-8-oxoguanine (1), 2-methylimino-3-methyl-6-methylamino- 9H-purine (2), 1,2,3,4-tetrahydro-betacarboline (3), 1,2,3,4-tetrahydro-1-methyl-beta-carboline (4) and 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (5) by comparison the spectroscopic data (MS, 1H, 13C-NMR) with those reported in the literatures. Compounds 2-5 were reported from the the genus Symplegma for the first time. The purine and carboline were the major alkaloid types of S. oceania.

Two new alkaloids, angustimine (1) featuring an unprecedented skeleton, and angustifolimine (2) being a rare diamino Daphniphyllum alkaloid, were isolated from Daphniphyllum angustifolium. Their structures were elucidated by extensive spectroscopic analysis. The biosynthetic origin of 1 was postulated. Cytotoxic activities of 1 and 2 were tested, and all of them were inactive.

The first chemical study on the stems and leaves of Daphniphyllum yunnanense led to the isolation of five new alkaloids, daphniyunnines A-E (1-5). Daphniyunnines B-E (2-5) are four unusual C-22 nor-Daphniphyllum alkaloids. The structures of these alkaloids were characterized by spectroscopic methods, especially 2D NMR techniques. A single-crystal X-ray diffraction analysis was used to confirm the structure of 1. Daphniyunnine D (4) showed cytotoxicity against two tumor cell lines, P-388 and A-549, with IC(50) values of 3.0 and 0.6 microM, respectively.