In vitro characterization of lamotrigine N2-glucuronidation and the lamotrigine-valproic acid interaction.
(25/92)
Studies were performed to investigate the UDP-glucuronosyltransferase enzyme(s) responsible for the human liver microsomal N2-glucuronidation of the anticonvulsant drug lamotrigine (LTG) and the mechanistic basis for the LTG-valproic acid (VPA) interaction in vivo. LTG N2-glucuronidation by microsomes from five livers exhibited atypical kinetics, best described by a model comprising the expressions for the Hill (1869 +/- 1286 microM, n = 0.65 +/- 0.16) and Michaelis-Menten (Km 2234 +/- 774 microM) equations. The UGT1A4 inhibitor hecogenin abolished the Michaelis-Menten component, without affecting the Hill component. LTG N2-glucuronidation by recombinant UGT1A4 exhibited Michaelis-Menten kinetics, with a Km of 1558 microM. Although recombinant UGT2B7 exhibited only low activity toward LTG, inhibition by zidovudine and fluconazole and activation by bovine serum albumin (BSA) (2%) strongly suggested that this enzyme was responsible for the Hill component of microsomal LTG N2-glucuronidation. VPA (10 mM) abolished the Hill component of microsomal LTG N2-glucuronidation, without affecting the Michaelis-Menten component or UGT1A4-catalyzed LTG metabolism. Ki values for inhibition of the Hill component of LTG N2-glucuronidation by VPA were 2465 +/- 370 microM and 387 +/- 12 microM in the absence and presence, respectively, of BSA (2%). Consistent with published data for the effect of fluconazole on zidovudine glucuronidation by human liver microsomal UGT2B7, the Ki value generated in the presence of BSA predicted the magnitude of the LTG-VPA interaction reported in vivo. These data indicate that UGT2B7 and UGT1A4 are responsible for the Hill and Michaelis-Menten components, respectively, of microsomal LTG N2-glucuronidation, and the LTG-VPA interaction in vivo arises from inhibition of UGT2B7. (+info)
Synthetic studies of complex immunostimulants from Quillaja saponaria: synthesis of the potent clinical immunoadjuvant QS-21Aapi.
(26/92)
QS-21 is one of the most promising new adjuvants for immune response potentiation and dose-sparing in vaccine therapy given its exceedingly high level of potency and its favorable toxicity profile. Melanoma, breast cancer, small cell lung cancer, prostate cancer, HIV-1, and malaria are among the numerous maladies targeted in more than 80 recent and ongoing vaccine therapy clinical trials involving QS-21 as a critical adjuvant component for immune response augmentation. QS-21 is a natural product immunostimulatory adjuvant, eliciting both T-cell- and antibody-mediated immune responses with microgram doses. Herein is reported the synthesis of QS-21A(api) in a highly modular strategy, applying novel glycosylation methodologies to a convergent construction of the potent saponin immunostimulant. The chemical synthesis of QS-21 offers unique opportunities to probe its mode of biological action through the preparation of otherwise unattainable nonnatural saponin analogues. (+info)
Purification and characterization of new special ginsenosidase hydrolyzing multi-glycisides of protopanaxadiol ginsenosides, ginsenosidase type I.
(27/92)
In this paper, the new type ginsenosidase which hydrolyzing multi-glycosides of ginsenoside, named ginsenoside type I from Aspergillus sp.g48p strain was isolated, characterized and generally described. The enzyme molecular weight was about 80 kDa. Ginsenosidase type I can hydrolyze different glycoside of protopanaxadiol type ginsenosides (PPD); i.e., can hydrolyze the 3(carbon)-O-beta-glucoside of Rb1, Rb2, Rb3, Rc, Rd; can hydrolyze 20(carbon)-O-beta-glucoside of Rb1, 20-O-beta-xyloside of Rb3, 20-O-alpha-arabinoside(p) of Rb2 and 20-O-alpha-arabinoside(f) of Rc to produce mainly F2, compound-K (C-K) and small Rh2, but can not hydrolyze the glycosides of protopanaxatriol type ginsenoside (PPT) such as Re, Rf, Rg1. So, when the ginsenosidase type I hydrolyzed ginsenosides, the enzyme selected ginsenoside-aglycone type, can hydrolyze different glycosides of PPD type ginsenoside; however no selected glycoside type, can hydrolyze multi-glycosides of PPD type ginsenosides. These properties were novel properties, and differentiated with the other previously described glycosidases. (+info)
Adjuvant effects of saponins on animal immune responses.
(28/92)
Vaccines require optimal adjuvants including immunopotentiator and delivery systems to offer long term protection from infectious diseases in animals and man. Initially it was believed that adjuvants are responsible for promoting strong and sustainable antibody responses. Now it has been shown that adjuvants influence the isotype and avidity of antibody and also affect the properties of cell-mediated immunity. Mostly oil emulsions, lipopolysaccharides, polymers, saponins, liposomes, cytokines, ISCOMs (immunostimulating complexes), Freund's complete adjuvant, Freund's incomplete adjuvant, alums, bacterial toxins etc., are common adjuvants under investigation. Saponin based adjuvants have the ability to stimulate the cell mediated immune system as well as to enhance antibody production and have the advantage that only a low dose is needed for adjuvant activity. In the present study the importance of adjuvants, their role and the effect of saponin in immune system is reviewed. (+info)
Antiestrogenic effect of 20S-protopanaxadiol and its synergy with tamoxifen on breast cancer cells.
(29/92)
BACKGROUND: 20S-protopanaxadiol (aPPD) is a major gastrointestinal metabolic product of ginsenosides. The latter share structural similarity with steroids and are the main pharmacologically active component in ginseng. METHODS: The authors investigated the interaction between aPPD and estrogen receptors (ER) in human breast adenocarcinoma MCF-7 cells through receptor binding assay, ER-induced gene expression, and cell proliferation both in vitro and in vivo. RESULTS: aPPD, but not its close analog ginsenosides, competed with the [(3)H]-17-beta estradiol (E2) for ER with IC(50) at 26.3 microM. aPPD alone weakly induced luciferase reporter-gene expression controlled by an estrogen-regulated element, which was completely blocked by tamoxifen. aPPD alone, or in synergy with tamoxifen, blocked E2-induced transcriptional activation. aPPD also inhibited colony formation of endometrial cancer cells. aPPD potently inhibited estrogen-stimulated MCF-7 cell proliferation and synergistically enhanced the cytotoxicity of tamoxifen on both ER+ MCF-7 and ER- MDA-MB231 cells. Furthermore, aPPD, but not tamoxifen, inhibited Akt phosphorylation. Growth of MCF-7 xenograft tumor supplemented with E2 was completely inhibited in animals treated with aPPD, tamoxifen, or aPPD plus tamoxifen. CONCLUSIONS: These results suggested that aPPD inhibits estrogen-stimulated gene expression and cell proliferation in ER-positive breast cancer cells. In addition, aPPD synergistically enhances cytotoxicity of tamoxifen in an ER-independent fashion, probably by down-regulating Akt activity. (+info)
ESR study on the structure and hydroxyl radical-scavenging activity relationships of ginsenosides isolated from Panax ginseng C A Meyer.
(30/92)
Ginsenosides have been regarded as the main active components of Panax ginseng C. A. Meyer, and the antioxidant activity of ginsenosides in vivo is well described. However, there has been virtually no report describing the direct free radical-scavenging activities of ginsenosides through the long history of ginseng research. The hydroxyl radical (*OH)-scavenging activity test using an electron spin resonance spectrometer (ESR) is suggested to be the most appropriate to measure the antioxidant activities of ginsenosides. Therefore, we investigated the *OH-scavenging and ferrous metal ion-chelating activities of several ginsenosides of Panax ginseng using ESR for the identification of active ginsenosides and its structure and activity relationships. As a result, 20(S)-Rg(3) showed the strongest activity, and the next were in the decreasing order of Rb(1), Rg(1), Rc, Rb(2), and Rd when dissolved with water. The *OH-scavenging activities of ginsenosides were related to the ferrous metal ion-chelating activities of their aglycone, 20(S)-protopanaxadiol. In addition, the ferrous metal ion-chelating activities of ginsenosides were thought to be influenced by their types of hydrophilic sugar moieties. (+info)
Esculeogenin A, a new tomato sapogenol, ameliorates hyperlipidemia and atherosclerosis in ApoE-deficient mice by inhibiting ACAT.
(31/92)
OBJECTIVE: We recently identified esculeoside A, a new spirosolane-type glycoside, with a content in tomatoes that is 4-fold higher than that of lycopene. In the present study, we examined the effects of esculeoside A and esculeogenin A, a new aglycon of esculeoside A, on foam cell formation in vitro and atherogenesis in apoE-deficient mice. METHODS AND RESULTS: Esculeogenin A significantly inhibited the accumulation of cholesterol ester (CE) induced by acetylated low density lipoprotein (acetyl-LDL) in human monocyte-derived macrophages (HMDM) in a dose-dependent manner without inhibiting triglyceride accumulation, however, it did not inhibit the association of acetyl-LDL to the cells. Esculeogenin A also inhibited CE formation in Chinese hamster ovary cells overexpressing acyl-coenzymeA (CoA): cholesterol acyl-transferase (ACAT)-1 or ACAT-2, suggesting that esculeogenin A suppresses the activity of both ACAT-1 and ACAT-2. Furthermore, esculeogenin A prevented the expression of ACAT-1 protein, whereas that of SR-A and SR-BI was not suppressed. Oral administration of esculeoside A to apoE-deficient mice significantly reduced the levels of serum cholesterol, triglycerides, LDL-cholesterol, and the areas of atherosclerotic lesions without any detectable side effects. CONCLUSIONS: Our study provides the first evidence that purified esculeogenin A significantly suppresses the activity of ACAT protein and leads to reduction of atherogenesis. (+info)
Marked production of ginsenosides Rd, F2, Rg3, and compound K by enzymatic method.
(32/92)
The hydrolysis of protopanaxadiol-type saponin mixture by various glycoside hydrolases was examined. Among these enzymes, crude preparations of lactase from Aspergillus oryzae, beta-galactosidase from A. oryzae, and cellulase from Trichoderma viride were found to produce ginsenoside F(2) [3-O-(beta-D-glucopyranosyl)-20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol], compound K [20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol], and ginsenoside Rd {3-O-[beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl]-20-O-beta-D-glucopyran osyl-20(S)-protopanaxadiol}, respectively, from protopanaxadiol-type saponin mixture in large quantities. Moreover, the crude preparation of lactase from Penicillium sp. having a high producing activity of ginsenoside Rh(1) (6-O-beta-D-glucopyranosyl-20(S)-protopanaxatriol) from protopanaxatriol-type saponin mixture gave ginsenoside Rd as a main product, ginsenoside Rg(3) {3-O-[beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl]-20(S)-protopanaxadiol} , and compound K from protopanaxadiol-type saponin mixture. The hydrolytic pathways of ginsenosides Rb(1), Rb(2), and Rc to ginsenosides Rd, Rg(3), and F(2), and compound K by crude preparations of four glycoside hydrolases were also studied. This is the first report on the enzymatic preparation of an intestinal bacterial metabolite, ginsenoside F(2), in quantity, and a considerable amount of a minor saponin, ginsenoside Rg(3), from a protopanaxadiol-type saponin mixture. (+info)