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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.

Eucalyptals A-C (1-3) with a new skeleton of 3,5-diformyl-isopentyl phloroglucinol-coupled cadinane were isolated from the fruits of Eucalyptus globulus. Their structures were elucidated by spectroscopic analysis, and that of 1 was confirmed by single-crystal X-ray diffraction. The biosynthetic pathway of 1-3 was also postulated. Compounds 1-3 exhibited selective cytotoxicity against the HL-60 cell line.

Chuktabularins A-D (1-4), four novel 16-norphragmalin-type limonoids that feature unprecedented skeletons with a biosynthetically extended C2 or C3 unit at C-15 forming a unique 2,7-dioxabicyclo[2.2.1]heptane moiety, were isolated from the stem bark of Chukrasia tabularis. Their structures were elucidated by spectroscopic analysis and computer modeling. The biosynthetic pathway of 1-4 was postulated.

Walsuronoid A (1), a limonoid featuring an unprecedented 3,4-peroxide-bridged A-seco skeleton, together with walsuronoids B (2) and C (3) possessing a rare 18(13-->14)-abeo-limonoid skeleton, was isolated from Walsura robusta. The structures were elucidated by spectroscopic analysis and chemical correlation, and that of 1 was confirmed by single-crystal X-ray diffraction. Biosynthetic pathway of 2 and 3 was proposed and was chemically mimicked. Compounds 1 and 2 showed weak antimalarial activity.

[reaction: see text] Four novel tetranortriterpenoids, xylogranatins A-D (1-4), with an unusual 9,10-seco skeleton were isolated from the seeds of a Chinese marine mangrove Xylocarpus granatum. Their structures were determined by spectroscopic and chemical means. Xylogranatin A (1) featured by a unique 1,9-oxygen bridge was confirmed by single-crystal X-ray diffraction, and xylogranatin D (4) with an unprecedented skeleton of C-30-C-9 linkage was postulated biogenetically from 3 via an alpha-hydroxyl ketone rearrangement and was chemically mimicked.

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.