Karin C. S. Chen Liu

Differential inhibition of reverse transcriptase and cellular DNA polymerase-α activities by lignans isolated from Chinese herbs, Phyllanthus myrtifolius Moon, and tannins from Lonicera japonica Thunb and Castanopsis hystrix

Two lignans, phyllamycin B and retrojusticidin B isolated from Phyllanthus myrtifolius Moon have been demonstrated to have a strong inhibitory effect on human immunodeficiency virus-1 reverse transcriptase activity (HIV-1 RT), but much less inhibitory effect on human DNA polymerase-alpha (HDNAP-alpha) activity. Fifty percent inhibitory concentrations of phyllamycin B and retrojusticidin B were determined to be 3.5 and 5.5 microM for HIV-1 RT, and 289 and 989 microM for HDNAP-alpha, respectively. The mode of inhibition was found to be non-competitive inhibition with respect to template-primer and triphosphate substrate. Several tannins such as caffeoylquinates (CQs) isolated from Lonicera japonica Thunb, galloylquinates (GQs) and galloylshikimates (GSs) purified from Castanopsis hystrix were shown to have a much less selective inhibitory effect on HIV-1 RT.

Lignans from Phyllanthus urinaria

Chemical investigation on the aerial and the root parts of Phyllanthus urinaria L. culminated in the isolation of four lignans, namely 5-demethoxyniranthin, urinatetralin, dextrobursehernin, urinaligran, together with nine known lignans. Their structures, including the absolute stereochemistry, were elucidated by spectral analysis (NMR and CD) and chemical correlation.

Six lignans from Phyllanthus myrtifolius.

Six lignans comprising phyllamyricins D (1), E (2), and F (3) and phyllamyricosides A (4), B (5), and C (6) were isolated in a continuing study of Phyllanthus myrtifolius. Compounds 1 and 2 are 2a-methoxy-4-aryl-2,3-naphthalides. Compounds 3-6 belong to the 4-arylnaphthalene class, with compounds 4-6 being O-beta-glucosides. Their structures were elucidated on the basis of spectral analysis. Compound 4 increased the activity of HIV-1 reverse transcriptase by 65% at a concentration of 1.89 microM.

Cyclopeptide alkaloids from stems of Paliurus ramossisimus.

Three 13-membered cyclopeptide alkaloids, paliurines G, H and I, together with six known alkaloids, nummularine H, daechuine-S3, paliurines A-C and F, were isolated from the stem of Paliurus ramossisimus by a combination of centrifugal partition chromatography and preparative TLC. Their structures were characterized and established on the basis of spectral analysis. A preliminary study indicated that nummularine H could shorten the methohexital induced sleeping time.

Production of Triterpenes from Cell Suspension Cultures of Solanum incanum L.

This paper describes the secondary metabolites produced by a cell suspension culture of Solanum incanum L. The investigation led to the characterization of five triterpenes, glut-5(6)-en-3β-ol (1), lupeol (2), betulin (3), betulinic acid (4) and betulinaldehyde (5). Their structures were determined on the basis of spectral analysis. Of these, betulinic acid, a potent anti-HIV agent, was found to be a major product. Glut-5(6)-en-3β-ol was a rare natural product.