Investigation of the alkaloids from Myrioneuron faberi, a plant unique to China, gave four pairs of enantiomers (1-4). (±)-β-Myrifabral A (1) and (±)-α-myrifabral A (2) formed an inseparable mixture of anomers (cluster A), as did (±)-β-myrifabral B (3) and (±)-α-myrifabral B (4) (cluster B). Their structures were determined by X-ray diffraction and NMR analysis. Compounds 1-4 possessed novel cyclohexane-fused octahydroquinolizine skeletons and represent the first quinolizidine alkaloids from the genus Myrioneuron. The epimers of cluster A (1 and 2) were modified and separated. In vitro, clusters A and B and their derivatives inhibited replication of hepatitis C virus (HCV, IC50 0.9 to 4.7 μM) with cytotoxicity lower than that of telaprevir.

Aphanamixoid A (1), a limonoid with a new carbon skeleton, along with its biogenetically related limonoid aphanamixoid B (2), was isolated from the leaves and twigs of Aphanamixis polystachya . Their structures with the absolute stereochemistry were determined by spectroscopic analysis, X-ray crystallography and computational methods. The significant antifeedant activity of 1 against the generalist plant-feeding insect Helicoverpa armigera (EC50 = 0.015 μmol/cm(2)) suggested it may be a potent defensive component of A. polystachya.

Fourteen new limonoids, munronins A-N (1-14), and eight known limonoids (15-22) were isolated from the whole plants of Munronia henryi. The structures of the new compounds were elucidated by 2D NMR spectroscopy and mass spectrometry, and the structure of 8 was confirmed by single-crystal X-ray diffraction analysis. Compound 1 represents the first limonoid found with a novel 7-oxabicyclo[2.2.1]heptane moiety produced by incorporating C-11 and C-14 via an oxygen atom. All compounds were evaluated for their anti-tobacco mosaic virus (TMV) activity and in vitro cytotoxicity against the human cancer HL-60, SMMC-7721, A-549, MCF-7, and SW-480 cell lines. Among them, compounds 2, 8, 9, 10, 11, 12, 18, and 20 showed significant anti-TMV activity, with IC50 values in the range 19.6-44.4 μg/mL. Compounds 1 and 18 exhibited cytotoxic effects for all five cancer cell lines, with IC50 values between 0.4 and 4.8 μM.