Structural Revision of a Naphthodipyranodione from Gentian Root and its Degradation Pathway from Gentiopicroside.

Based on NOE experiments, the structure of naphthodipyranodione from Gentianaceae plants was revised to 1,2-dihydro-4H,6H,8H-naphto[1,2-d:4,5- c'd']dipyrano-4,8-dione. Naphthodipyranodione was assumed to be formed by the degradation of gentiopicroside by enzymatic hydrolysis at low water -concentration. The degradation pathway was a unique domino-reaction triggered by enzymatic hydrolysis. Naphthodipyranodione may become an index compound for the drying and/or fermenting procedure of Gentian root.

Differential effect of schisandrin B stereoisomers on ATR-mediated DNA damage checkpoint signaling.

We have previously reported that schisandrin B (SchB) is a specific inhibitor of ATR (ataxia telangiectasia and Rad-3-related) protein kinase. Since SchB consists of a mixture of its diastereomers gomisin N (GN) and γ-schisandrin (γ-Sch), the inhibitory action of SchB might result from a stereospecific interaction between one of the stereoisomers of SchB and ATR. Therefore, we investigated the effect of GN and γ-Sch on UV (UVC at 254 nm)-induced activation of DNA damage checkpoint signaling in A549 cells. UV-induced cell death (25 - 75 J/m(2)) was amplified by the presence of the diastereomers, especially GN. At the same time, GN, but not γ-Sch, inhibited the phosphorylation of checkpoint proteins such as p53, structural maintenance of chromosomes 1, and checkpoint kinase 1 in UV-irradiated cells. Moreover, GN inhibited the G2/M checkpoint during UV-induced DNA damage. The in vitro kinase activity of immunoaffinity-purified ATR was dose-dependently inhibited by GN (IC50: 7.28 µM) but not by γ-Sch. These results indicate that GN is the active component of SchB and suggest that GN inhibits the DNA damage checkpoint signaling by stereospecifically interacting with ATR.

Achyranthoside H methyl ester, a novel oleanolic acid saponin derivative from Achyranthes fauriei roots, induces apoptosis in human breast cancer MCF-7 and MDA-MB-453 cells via a caspase activation pathway.

Achyranthoside H methyl ester (AH-Me) is an oleanolic acid saponin derivative isolated from the roots of Achyranthes fauriei through diazomethane treatment. AH-Me exhibited significant cytotoxicity against human breast cancer MCF-7 and MDA-MB-453 cells, with respective ID(50) values of 4.0 and 6.5 muM: in the MTT assay. AH-Me is a unique saponin containing three methoxycarbonyl groups in the sugar moiety linked to the C-3 position of oleanolic acid. The demethylation of these methoxycarbonyl groups by alkaline hydrolysis caused a marked reduction of the cytotoxicity of AH-Me, suggesting that the methoxycarbonyl groups of AH-Me are key groups for the acquisition of cytotoxicity against human cancer cells. The staining of cancer cells with 4',6'-diamidino-2-phenylindole (DAPI) showed that the population of cells with altered nuclear morphology, for example chromatin condensation and fragmentation, increased markedly after AH-Me treatment. Exposure of MCF-7 and MDA-MB-453 cells to AH-Me resulted in a dose-dependent and time-dependent increase in the sub-G1 population, and in the cleavage of poly-ADP-ribose polymerase (PARP) followed by the formation of an 89 kD peptide. Pretreatment of the cells with the pan-caspase inhibitor z-VAD-fmk abolished the cleavage of PARP by AH-Me treatment and suppressed the antiproliferative effect of AH-Me on tumor cell growth. These results together led to the suggestion that AH-Me induces apoptosis via the caspase activation pathway in human breast cancer cells, and apoptosis is the major mode of the cytotoxic effect triggered by AH-Me.

Two new glucuronide saponins, Achyranthosides G and H, from Achyranthes fauriei root.

Two oleanolic acid saponins named achyranthosides G (1) and H (2) were newly isolated from Achyranthes fauriei root as methyl esters in addition to methyl esters of achyranthosides A - F and five oleanolic acid glucuronides (chikusetsusaponins IVa, V, 28-deglucosyl chikusetsusaponin V, pseudoginsenoside RT(1), and oleanolic acid 3-O-beta-D-glucuronopyranoside) as well as oleanolic acid 28-O-beta-D-glucopyranoside, beta-ecdysterone, and polypodine B. Their structures were characterized as follows on the basis of the chemical and spectroscopic evidences.

Lupane-type saponins from leaves of Acanthopanax sessiliflorus and their inhibitory activity on pancreatic lipase.

Three known saponins, chiisanoside, 11-deoxyisochiisanoside, and isochiisanoside, and one novel saponin, 3,4-seco-4(23),20(29)-lupadiene-3,28-dioic acid 28-O-alpha-l-rhamnopyranosyl (1-->4)-beta-d-glucopyranosyl (1-->6)-beta-d-glucopyranoside, referred to as sessiloside, were isolated from a hot water extract of Acanthopanax sessiliflorus leaves. All of these saponins were lupane-type triterpene triglycosides, and their concentrations were 4.1, 1.0, 0.5, and 0.4% (w/w) of the total extract, respectively. Sessiloside and chiisanoside inhibited pancreatic lipase activity in vitro, and addition of the saponin-rich fraction to a high-fat diet suppressed the body weight gain of mice. The possibility of application of the lupane-type saponins from A. sessiliflorus leaves to the treatment of obesity is discussed.