Potential modulation on P-glycoprotein and CYP3A by soymilk and miso: in vivo and ex-vivo studies.

P-glycoprotein (P-gp) and CYP3A4 both play very important roles in drug bioavailability, resistance and interactions. Our in vitro studies indicated that P-gp function was activated by many isoflavones. This study investigated the in vivo effects of soymilk and miso, isoflavone-rich soy foods, on P-gp and CYP3A by tracing the pharmacokinetics of cyclosporine (CSP), a probe drug of P-gp. Rats were orally administered CSP with and without soymilk or miso. A specific monoclonal fluorescence polarisation immunoassay was used to determine the blood concentration of CSP. The results showed that soymilk and miso significantly decreased the C(max) of CSP by 64.5% and 78.3%, and reduced the AUC(0-540) by 64.9% and 78.3%, respectively. Mechanism studies revealed that the activities of P-gp and CYP3A4 were induced by soymilk and miso. In conclusion, ingestion of soymilk and miso significantly activated the functions of P-gp and CYP3A.

Metabolism and pharmacokinetics of genipin and geniposide in rats.

Geniposide, an iridoid glucoside, is a major constituent in the fruits of Gardenia jasminoides (Gardenia fruits), a popular Chinese herb. Genipin, the aglycone of geniposide, is used to prepare blue colorants in food industry and also a crosslinking reagent for biological tissue fixation. In this study, we investigated the metabolism and pharmacokinetics of genipin and geniposide in rats. Blood samples were withdrawn via cardiopuncture and the plasma samples were assayed by HPLC method before and after hydrolysis with sulfatase and beta-glucuronidase. The results indicated that after oral administration of genipin or Gardenia fruit decoction, genipin sulfate was a major metabolite in the bloodstream, whereas the parent forms of genipin and geniposide were not detected. Importantly, oral administration of 200mg/kg of genipin resulted in a mortality of 78% (7/9) in rats.

Marked decrease of cyclosporin bioavailability caused by coadministration of ginkgo and onion in rats.

Quercetin was reported to modulate CYP isoenzymes and P-glycoprotein (Pgp), a drug efflux transporter. Our previous study reported that quercetin significantly decreased the bioavailability of cyclosporin, a substrate for CYP3A4 and Pgp, in rats and pigs. Ginkgo and onion contain quercetin and its glycosides as St. John's Wort. The coadministration of cyclosporin with ginkgo or onion may be subject to clinically relevant interactions as St. John's Wort. Therefore, this study aimed to investigate the influences of ginkgo and onion on the absorption and disposition of cyclosporin in rats. Cyclosporin was administered orally and intravenously to rats with and without an oral dose of ginkgo or onion in crossover designs. Blood samples were collected via cardiopuncture and blood cyclosporin concentration was assayed by a specific monoclonal fluorescence polarization immunoassay. Everted gut sac was used to investigate the effects of ginkgo and onion on the function of intestinal Pgp. Oral coadministration of ginkgo and onion significantly decreased the Cmax of cyclosporin by 62% and 60%, and reduced the AUC0-t by 51% and 68%, respectively, whereas no influence was observed when cyclosporin was given intravenously. This indicates that the interactions between cyclosporin and ginkgo or onion occurred mainly at the absorption site. In conclusion, ginkgo and onion markedly decreased the oral bioavailability of cyclosporin. We suggest that concurrent intake of quercetin-rich herbs or foods with cyclosporin are better avoided in order to ensure the efficacy of cyclosporin.

Morin sulphates/glucuronides enhance macrophage function in microgravity culture system.

BACKGROUND: The immune system changes significantly in astronauts during and after space flight. Although the mechanism has not been defined, it is reasonable to begin developing effective countermeasures to the physiological consequences of spaceflight, especially immunosuppression. Many studies have been published about the effect of flavonoids on immune modulation. Thus, the aim of this study was to develop whether flavonoids could be the effective countermeasures to the immunosuppression caused by microgravity. MATERIALS AND METHODS: We used a rotating wall vessel 3D (three-dimensional) culture system which recreates some of the culture conditions that occur during microgravity to study the effects of microgravity on the function of macrophages and assess the modulating effects of flavonoids on microgravity-induced macrophage dysfunction. RESULTS: We demonstrated 65% and 80% reduction in mitogen-induced nitric oxide and cytokine production of 3D-cultured macrophages, compared to conventional two-dimensional (2D)-cultured cells. Moreover, the microgravity-induced macrophage dysfunction was not restored by transferring cells from 3D to 2D culture. However, the addition of morin sulphates/glucuronides in 3D culture compensated for the loss of macrophage function. CONCLUSION: The result presented here suggests for the first time that an immune-modulatory strategy using flavonoid supplements such as morin would benefit the health of astronauts.

Effects of glucose, fructose and 5-hydroxymethyl-2-furaldehyde on the presystemic metabolism and absorption of glycyrrhizin in rabbits.

Our previous study reported that co-administration of honey significantly increased the serum levels of glycyrrhetic acid (GA) after oral administration of glycyrrhizin (GZ) in rabbits. The components of honey are sucrose, glucose, fructose and 5-hydroxymethyl-furaldehyde (HMF). To clarify the causative component(s) in honey that altered the metabolic pharmacokinetics of GZ, rabbits were given GZ (150 mg kg(-1)) with and without glucose (5 g/rabbit), fructose (5 g/rabbit) and HMF (1 mg kg(-1)), respectively, in crossover designs. An HPLC method was used to determine concentrations of GZ and GA in serum as well as GA and 3-dehydroglycyrrhetic acid (3-dehydroGA) in faeces suspension. A noncompartment model was used to calculate the pharmacokinetic parameters and analysis of variance was used for statistical comparison. Our results indicated that the area under curve (AUC) of GA was significantly increased by 29% when HMF was coadministered, whereas the pharmacokinetics of GZ and GA were not significantly altered by coadministration of glucose or fructose. An in-vitro study, using faeces to incubate GZ and GA individually, indicated that HMF significantly inhibited the oxidation of GA to 3-dehydroGA and this may explain the enhanced GA absorption in-vivo. It was concluded that HMF is the causative component in honey that affects the presystemic metabolism and pharmacokinetics of GZ in-vivo.

Profound difference in pharmacokinetics between morin and its isomer quercetin in rats.

Morin and quercetin are isomeric antioxidant flavonols widely distributed in plant foods and herbs. The pharmacokinetics of both flavonols at two doses were investigated and compared in rats. Parent forms and their glucuronides and sulfates in serum were determined by HPLC before and after enzymatic hydrolysis, respectively. After oral dosing of morin, both the parent form, morin, and its glucuronides and sulfates were present in the bloodstream. The conjugated metabolites predominated at the dose of 25 mg kg(-1), whereas the parent form was predominant at the dose of 50 mg kg(-1). Moreover, the AUC of morin parent form increased by a factor of 37 when the dose doubled, indicating that morin showed nonlinear pharmacokinetics. On the other hand, quercetin presented only as glucuronides and sulfates in the blood, indicating negligible bioavailability of quercetin, and the metabolites showed linear pharmacokinetics at the two doses studied. When considering the total AUC of parent form with conjugated metabolites, the extent of absorption of morin was 3 fold that of quercetin at the dose of 50 mg kg(-1). The results indicated that the difference in hydroxylation pattern on B-ring of flavonol markedly affected their fates in rats.

Quercetin glucuronides inhibited 2-aminofluorene acetylation in human acute myeloid HL-60 leukemia cells.

Our earlier study has demonstrated that following the exposure of rat to the arylamine carcinogen 2-aminofluorene, DNA-2-aminofluorene adducts were found in the target tissues liver, bladder, colon, lung and also in circulating leukocytes (lymphocytes and monocytes). The result also demonstrated that orally treated antioxidants decreased N-acetylation of 2-aminofluorene in target tissues and leukocytes. Therefore, this study investigated whether quercetin glucuronides could affect N-acetylation of 2-aminofluorene in human acute myeloid leukemia HL-60 cells. Evidence is presented here that human leukemia cells are capable of acetylating 2-aminofluorene. Quercetin glucuronides did inhibit 2-aminofluorene acetylation in intact cells. The results also indicated that quercetin glucuronides induced cytotoxicity in dose-dependent manner in the examined human acute myeloid leukemia HL-60 cells.

Determinations of morin, quercetin and their conjugate metabolites in serum.

Morin and quercetin are isomeric antioxidant flavonols. High-performance liquid chromatographic methods were developed for the quantitation of morin and quercetin in serum. The method employed a Cosmosil RP-18 column, using acetonitrile/0.2% o-phosphoric acid 28/72 and 27/73 (v/v) as mobile phases, with ethyl paraben and 6,7-dimethoxycoumarin used as internal standards for morin and quercetin, respectively. Moreover, a strategy to stabilize morin/quercetin released from their glucuronides/sulfates in serum during hydrolysis was established. The present methods are applicable for determining morin, quercetin, and their glucuronides/sulfates in serum.

Effect of honey and sugars on the metabolism and disposition of naringin in rabbits.

To investigate the effect of honey and sugars on the metabolism and disposition of naringin, rabbits were administered naringin alone and naringin with honey or its component sugars - fructose, glucose and sucrose in crossover designs. An HPLC method was developed to determine naringenin in serum after enzymatic hydrolysis. Our results indicate that honey, fructose and sucrose significantly reduced AUC(0-t) of naringenin by 41 %, 61 % and 45 %, respectively. In vitro studies using a rabbit feces suspension to incubate naringin without or with honey or the respective sugars were employed to investigate the mechanism of this interaction. The results indicated that honey and its component sugars did not affect the rate and extent of naringin hydrolysis, whereas the degradation of naringenin was significantly enhanced in the presence of honey and fructose. It could be concluded that concomitant intake of honey, fructose and sucrose resulted in the reduction of naringin absorption which could be attributable in part to the enhanced preabsorption degradation of absorbable naringenin in the large intestine.

Acute intoxication of cyclosporin caused by coadministration of decoctions of the fruits of Citrus aurantium and the Pericarps of Citrus grandis.

In order to investigate the effects of Citrus herbs on cyclosporin absorption and disposition, swine were given cyclosporin (10 mg/kg) with or without decoctions of Citri Aurantii Fructus (CAF) or Citri Grandis Pericarpium (CGP) in a crossover design. FPIA method (fluorescence polarization immunoassay) was used to determine the blood concentration of cyclosporin. The decoctions were characterized by their flavanone contents. Our results indicated that the coadministration of CAF and CGP significantly increased the Cmax of cyclosporin by 64% and 79%, respectively. The AUC of cyclosporin was significantly elevated by 97% when coadministered with CGP. Among the swine, 1/5 and 3/5 exhibited acute toxicity of cyclosporin after concomitant intake of CAF and CGP, respectively. This indicates an interaction of Citrus compounds with a commonly used drug. We suggest when cyclosporin is coadministered with these Citrus decoctions, the blood concentration of cyclosporin should be carefully monitored for dose adjustment to avoid cyclosporin intoxication.

Effect of honey on naringin absorption from a decoction of the pericarps of Citrus grandis.

To measure naringin/naringenin absorption of a decoction prepared from the pericarps of Citrus grandis and to investigate the effect of honey on naringin/naringenin absorption, six healthy males received 200 mL decoctions of untreated and honey-treated Pericarpium Citri Grandis in a randomized crossover design. The absorption was measured by renal recovery of naringenin glucuronides/sulfates over 48 hours. The contents of naringin/naringenin in 200 mL decoctions of untreated and honey-treated Pericarpium Citri Grandis were determined to be 261.5/23.8 mumol and 303.3/11.6 mumol, respectively. The mean cumulated renal excretion of naringenin glucuronides/sulfates after intake of these two decoctions were 74.8 mumol (26.2% of dose) and 49.8 mumol (15.8% of dose), respectively. Paired Student's t-test showed that the difference of the total renal recovery of naringin/naringenin between the two decoctions was significant. The results indicated that honey significantly reduced naringin/naringenin absorption by 33.4% in humans and suggested that honey treatment might alter the efficacy of Pericarpium Citri Grandis.

Honokiol and magnolol increased hippocampal acetylcholine release in freely-moving rats.

Honokiol and magnolol, phenolic compounds isolated from the stem bark of Magnolia officinalis, have been demonstrated to increase choline acetyltransferase activity, inhibit acetylcholinesterase, promote potassium-induced acetylcholine release and exhibit neurotrophic function in in vitro studies. The objective of the present study was to determine the effect of these compounds on hippocampal acetylcholine release in conscious, freely-moving rats. 10(-4) M-10(-6) M of honokiol or magnolol was perfused into rat hippocampus via a dialysis probe. The results showed that at 10(-4) M concentration, honokiol and magnolol markedly increased extracellular acetylcholine release to 165.5+/-5.78% and 237.83+/-9.47% of the basal level, respectively. However, lower concentrations of either compounds failed to elicit significant acetylcholine release. This result suggests that a high dose of honokiol or magnolol may enhance in vivo hippocampal acetylcholine release.

Terpenoids of Syzygium formosanum.

A new natural product, 4-epifriedelin (1), and 12 known terpenoids have been isolated from the leaves of Syzygium formosanum. The known compounds include caryophyllene oxide, friedelin, canophyllal, glutinol, alpha-terpineol, phytol, betulinic acid, uvaol, lupeol, betulin, ursolic acid, and oleanolic acid. All of these compounds are reported for the first time from S. formosanum.

Constituents and bioactive principles of Polygonum chinensis.

Isolation and characterization of the chemical constituents of Polygonum chinensis L. gave the new 25R-spirost-4-ene-3,12-dione. The known compounds stigmast-4-ene-3,6-dione, stigmastane-3,6-dione, hecogenin and aurantiamide acetate were also isolated from for the first time from this species. Their anti-inflammatory and anti-allergic properties are described.

Comparison of the effects of cimetidine and ranitidine on the pharmacokinetics of disopyramide in man.

The widely prescribed antiulcer agents cimetidine and ranitidine have the potential to affect the absorption, metabolism or renal excretion of disopyramide. This study investigated the effect of a single oral dose of cimetidine or ranitidine on the pharmacokinetics of disopyramide and mono-N-dealkyldisopyramide in six healthy volunteers. The treatment was conducted in a randomized cross-over design. Serum levels and urinary recoveries of disopyramide and mono-N-dealkyldisopyramide were assayed by HPLC. Cimetidine significantly elevated the maximum plasma concentration of disopyramide, the area under the plasma concentration-time curve and the total amount of disopyramide excreted unchanged in the urine, but the serum profile of mono-N-dealkyldisopyramide was not significantly affected. The effects of ranitidine on the pharmacokinetics of disopyramide and mono-N-dealkyldisopyramide were not significant. The interaction between cimetidine and disopyramide occurred mainly at the site of absorption. The results indicate that cimetidine, but not ranitidine, significantly increased the absorption of orally administered disopyramide.

Emodin pharmacokinetics in rabbits.

Administration of emodin to rabbits by i.v. bolus resulted in a serum profile which could be well described by a two-compartment model. The AUC of emodin was 518 micrograms.min/ml, clearance was 72.3 ml/min, and elimination half life was 227 min which was much longer than that reported in a previous study. Oral administration of emodin resulted in a very low serum concentration. Protein binding of emodin was investigated by the equilibrium dialysis method. Emodin was found to be highly bound (99.6%) to serum protein.

Vasorelaxant effect of emodin, an anthraquinone from a Chinese herb.

The possible mechanism underlying the vasorelaxant effect of emodin isolated from a Chinese herb, was investigated in this study. Emodin dose dependently relaxed isolated vascular rings of human internal mammary artery and saphenous vein, rabbit thoracic aorta, abdominal aorta and mesenteric artery, and rat thoracic aorta. There were no differences in the sensitivity (IC50) and maximal relaxation between intact and endothelium-denuded preparations of rat aorta. In the presence of emodin (10 microM), the contractile responses of rat aorta to phenylephrine, serotonin and potassium chloride were depressed. The relaxation response to acetylcholine was attenuated by emodin, whereas that to isoproterenol was unaffected. The relaxation response to emodin was inhibited by free radical scavengers, superoxide dismutase, catalase and mannitol, and guanylate cyclase inhibitors, methylene blue and hemoglobin. Catalase was the most effective scavenger. Quinacrine (phospholipase A2 inhibitor), indomethacin (cyclooxygenase inhibitor) and nordihydroguaiaretic acid (NDGA, lipoxygenase inhibitor) potentiated the relaxation induced by emodin. NDGA was the most effective potentiator. Exposure of aortic rings to emodin (10 microM) increased the basal level of guanosine 3',5'-cyclic monophosphate (cGMP). It is suggested that the vasorelaxant effect of emodin may be mainly due to cGMP accumulation as a result of guanylate cyclase activation by free radicals and/or hydrogen peroxide generated from semiquinone.

Vasorelaxants from Chinese herbs, emodin and scoparone, possess immunosuppressive properties.

Emodin and scoparone, the active principles isolated from Polygonum multiflorum and Artemisia scoparia, respectively, both exhibit vasorelaxant and immunosuppressive effects. Emodin (10(-6)-3 x 10(-5) M) and scoparone (10(-6)-3 x 10(-5) M) dose dependently relaxed rat thoracic aortic rings precontracted with phenylephrine. Emodin (3 x 10(-7)-10(-4) M) and scoparone (10(-6)-3 x 10(-4) M) also dose dependently suppressed the responses of human mononuclear cells to phytohemagglutinin and mixed lymphocyte reaction. These compounds may be useful as new templates for the development of better immunosuppressive agents with vasorelaxant actions for use against transplantation rejection and autoimmune disease.

Dose dependent effect of cimetidine on procainamide disposition in man.

This study investigated the influence of single dose of 200 mg and 400 mg cimetidine on the pharmacokinetics of procainamide (PA) in healthy Chinese. The results show that AUC of PA was significantly raised by 38% and 24% with a significant reduction in renal clearance by 40% and 31%, respectively, when single dose of 400 mg or 200 mg cimetidine was coadministered. Significant changes of AUC and renal clearance of the active metabolite--N-acetylprocainamide (NAPA) were found only following the dose of 400 mg cimetidine. The larger dose of cimetidine produced greater alteration in the PA and NAPA pharmacokinetics. The interaction is mainly associated with their reduced renal clearance.