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At least 757 records · Page 42Linked to original sources
PubMed2006

Microbial metabolism of the prenylated chalcone xanthohumol.

Microbial metabolism of xanthohumol (1), a prenylated chalcone isolated from hops, gave three novel glucosylated derivatives (2-4) and a known compound, isoxanthohumol (5). The structures of the new compounds were identified as xanthohumol 4'-O-beta-glucopyranoside (2), xanthohumol 4,4'-O-beta-diglucopyranoside (3), and 5-methoxy-8-prenylnaringenin 7-O-beta-glucopyranoside (4) on the basis of spectroscopic methods.

Chalcone↗
PubMedDate not supplied

Retrodihydrochalcones from Dracaena loureiri.

The first four members of a new class of natural products, the retrodihydrochalcones, have been isolated from the leaves of Dracaena loureiri. The structures of the loureirins 1-4 were elucidated through interpretation of their spectroscopic data, with particular use being made of the selective INEPT nmr technique.

Chalcone↗
PubMedDate not supplied

Isolation of flavonoids and a chalcone from Helichrysum odoratissimum and synthesis of helichrysetin.

3,5-Dihydroxy-6,7,8-trimethoxyflavone, 3-O-methylquercetin, and helichrysetin were isolated from the flowers of the Rwandese medicinal plant, Helichrysum odoratissimum. Because of inconsistencies of the mp of the latter chalcone, a synthesis of helichrysetin was developed. 3-O-Methylquercetin was shown to be an active principle as it displayed antimicrobial activity.

Anti-Infective Agents↗
PubMedDate not supplied

Kukulkanins A and B, new chalcones from Mimosa tenuefolia.

Two new methoxychalcones, kukulkanins A (2',4'-dihydroxy-3',4-dimethoxychalcone) and B (2',4',4-trihydroxy-3'-methoxychalcone), were isolated by flash chromatography of extracts of small branches of Mimosa tenuefolia. The compounds were identified using ir, nmr, uv, and mass spectroscopy, and their structures were confirmed by X-ray crystallography.

Chalcone↗
PubMed1993

Two new cytotoxic chalcones from Calythropsis aurea.

The crude extract of Calythropsis aurea (Myrtaceae) produced a pattern of differential cytotoxicity in the NCI 60 cell line assay which was similar to those of known tubulin-interactive compounds. Cytotoxicity-guided fractionation led to the isolation of two new chalcones, calythropsin [1] and dihydrocalythropsin [2], which were responsible for the activity. Calythropsin was demonstrated to have a weak effect on mitosis, and presumably also on tubulin polymerization.

Animals↗
PubMed2003

Inhibition of peroxynitrite-mediated LDL oxidation by prenylated flavonoids: the alpha,beta-unsaturated keto functionality of 2'-hydroxychalcones as a novel antioxidant pharmacophore.

Prenylated 2'-hydroxychalcones and flavanones from the inflorescences of the female hop plant (Humulus lupulus) were shown to inhibit peroxynitrite-mediated oxidation of low-density lipoproteins (LDL) at low micromolar concentrations. LDL oxidation was induced by the peroxynitrite generator, 3-morpholinosydnonimine (SIN-1), and measured by the formation of conjugated dienes and thiobarbituric reactive substances. Human intake of prenylated chalcones and flavanones is mainly through beer, which contains up to 4 mg/L of these polyphenols. The two main oxidation products obtained by SIN-1 and peroxynitrite treatment of xanthohumol (XN), the principal prenylflavonoid of hops, were the aurone, auroxanthohumol (AUXN), and an endoperoxy derivative of XN, named endoperoxyxanthohumol (EPOX). In addition, the reaction produced smaller amounts of the nitro and nitroso derivatives of XN and EPOX. The formation of these nitrated products was enhanced in the presence of sodium bicarbonate (25 mM). SIN-1-induced formation of AUXN is considered to be a superoxide-mediated reaction, while the structure of EPOX points to a two electron oxidation reaction involving a Michael type addition with peroxynitrite as the nucleophile, followed by cyclization yielding a (1,2)-dioxepin-5-one ring structure. The flavanone isomer of XN, isoxanthohumol (IsoXN), unexpectedly showed a slight prooxidant effect instead of an inhibitory effect on LDL oxidation. Except for the formation of minor nitrated products, IsoXN remained largely unmodified upon treatment with SIN-1/peroxynitrite. Taken together, our results suggest that the alpha,beta-unsaturated keto functionality of chalcones is most reactive toward superoxide and peroxynitrite anions.

Antioxidants↗
PubMed2005

Xanthohumol isolated from Humulus lupulus Inhibits menadione-induced DNA damage through induction of quinone reductase.

The female parts of hops (Humulus lupulus L.) show estrogenic effects as well as cancer chemopreventive potential. We analyzed the chemopreventive mechanism of hops by studying its antioxidative activities and its effect on the detoxification of a potentially toxic quinone (menadione). The detoxification enzyme quinone reductase [(NAD(P)H:quinone oxidoreductase, QR] protects against quinone-induced toxicity and has been used as a marker in cancer chemoprevention studies. Although the hop extract was only a weak quencher of free radicals formed from 1,1-diphenyl-2-picrylhydrazyl, it demonstrated strong QR induction in Hepa 1c1c7 cells. In addition, compounds isolated from hops including xanthohumol (XH) and 8-prenylnaringenin were tested for QR induction. Among these, XH was the most effective at inducing QR with a concentration required to double the specific activity of QR (CD value) of 1.7 +/- 0.7 microM. In addition, pretreatment of Hepa1c1c7 cells with XH significantly inhibited menadione-induced DNA single-strand breaks. The QR inhibitor dicumarol reversed the protective effect of XH against menadione-induced DNA damage. Because the expression of QR and other detoxifying enzymes is known to be upregulated by binding of the transcription factor Nrf2 to the antioxidant response element (ARE), the reporter activity mediated by ARE in HepG2-ARE-C8 cells was investigated after incubation with XH for 24 h. Under these conditions, XH increased ARE reporter activity in a dose-dependent manner. One mechanism by which XH might induce QR could be through interaction with Keap1, which sequesters Nrf2 in the cytoplasm, so that it cannot activate the ARE. Using LC-MS-MS, we demonstrated that XH alkylates human Keap1 protein, most likely on a subset of the 27 cysteines of Keap1. This suggests that XH induces QR by covalently modifying the Keap1 protein. Therefore, XH and hops dietary supplements might function as chemopreventive agents, through induction of detoxification enzymes such as QR.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Intestinal first-pass metabolism of eperisone in the rat.

PURPOSE: The purpose of this study was to clarify quantitatively the contribution of the intestine to the first-pass metabolism of eperisone in rats. METHODS: The systemic availabilities of eperisone were estimated by administering the drug into the duodenum, portal vein, and femoral vein in rats in vivo. The first-pass metabolism of eperisone was confirmed in the perfused rat small intestine in situ. Metabolism of eperisone to an omega-1-hydroxylated metabolite (HMO), the first step of eperisone metabolism, was studied using rat intestinal microsomes in vitro. RESULTS: The bioavailabilities in the intestine were 0.176 and 0.0879 at administration rates of 100 and 25 mg/h/kg, respectively, whereas those in the liver were 0.532 and 0.486, respectively. In the intestinal perfusion experiment, the appearance clearance to the portal vein from the intestinal lumen was much lower than the elimination clearance from the intestinal lumen, resulting in high metabolic clearance of eperisone in the small intestine. Eperisone was biotransformed to HMO by rat intestinal microsomes, and this was inhibited by alpha-naphthoflavone and an anti-rat CYP1A antibody. CONCLUSIONS: Those data strongly suggest that eperisone may be metabolized to HMO by CYP1A in rat intestinal microsomes during the first-pass through the epithelium of the small intestine.

Algorithms↗
PubMed2002

Effect of carboxamide derivative IS-741 on rat spontaneous chronic pancreatitis.

This study aimed to analyze the therapeutic effects of the carboxamide derivative IS-741 on spontaneous chronic pancreatitis (CP) in the WBN/Kob rat. Four-week-old male WBN/Kob rats were fed with MB-3, and IS-741 (0.012% in MB-3) was orally administered for 12 weeks. Cytokine-induced neutrophil chemoattractant (CINC), interleukin (IL) -6, pancreatitis-associated protein (PAP), and p8 mRNAs in the pancreas were detected with semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Histological examination of the pancreas showed that hemorrhage, interstitial edema, and inflammatory cell infiltration were markedly less severe at 12 weeks, while fibrosis and acinar degeneration were also milder at 16 weeks, in the IS-741-treated rats than in untreated rats. The above-mentioned genes were significantly suppressed in IS-741-treated rats at 12 weeks. Our results show that IS-741 exerts a potentially therapeutic effect on experimental CP by suppressing the expressions of the proinflammatory cytokines (IL-6 and CINC) and pancreatic acute phase proteins (PAP and p8).

Administration, Oral↗
PubMed2000

A full-UV spectrum absorbing daily use cream protects human skin against biological changes occurring in photoaging.

BACKGROUND: There is overwhelming evidence that exposure of human skin to ultraviolet radiations (UVR) leads to the development of cutaneous photoaging and eventually to neoplasia. This study was designed to evaluate in humans the protection afforded by a daily use cream containing a photostable combination of UVB and UVA absorbers (Uvinul N539, Parsol 1789 and Mexoryl SX) providing a continuous absorption through the entire UV spectrum, against damages induced by repeated daily exposure to solar simulated radiation (SSR). METHODS: Buttock skin of 12 healthy volunteers was exposed 5 days per week for 6 weeks to one minimal erythema dose of solar simulated radiation per exposure. The following parameters in treated and untreated skin were evaluated: erythema, pigmentation, skin hydration, skin microtopography, histology and immunochemistry, and collagen and metalloproteinase (MMP) mRNA levels. RESULTS: In SSR exposed unprotected skin sites, we observed melanization and changes in the skin hydration and microtopography. The epidermis revealed a significant increase in stratum corneum and stratum granulosum thickness. In the dermis, an enhanced expression of tenascin and a reduced expression of type I pro-collagen were evidenced just below the dermal epidermal junction. Although we were unable to visualize any change in elastic fibers in exposed buttock skin, a slightly increased deposition of lysozyme and alpha 1 antitrypsin on these fibers was observed using immunofluorescence techniques. Furthermore, types I and III collagen mRNA were slightly increased and a significant enhancement (up to 2.8-fold) of MMP-2 mRNA level was observed. The daily use cream was shown to prevent all these biological changes. CONCLUSION: Our results show in vivo that an appropriate full-UV spectrum product significantly reduces the solar-UV-induced skin damage, demonstrating the benefit of daily photoprotection.

Acrylates↗
PubMed1975

Modest radiosensitization of solid tumours in C3H mice by the hypoxic cell radiosensitizer NDPP.

The x-ray dose required to cure half the mice bearing first generation transplanted mammary carcinomata 150 days after irradiation was determined. NDPP proved to be a relatively poor radiosensitizer in mice, for although a maximum enhancement ratio of 1-3 was obtained when x-rays produced from a 1-4 MeVp electron accelerator were given between 10 and 17 min after the administration of NDPP, this was at a drug concentration sufficient to cause marked kidney abnormalities in 5-10% of the mice.

Animals↗