Biosynthetic (14)C-labelling of xanthohumol in hop cones

Xanthohumol (Xn) has well-established chemopreventive potential in vitro. In order to carry out in vivo bioavailability and tissue distribution studies,( 14)C-labelled Xn was produced by biolabelling. Supplying hop sprouts with 5 mCi [U-(14)C]glucose led to incorporation of (14)C into Xn. Delivering the radioactive precursor at once resulted in Xn with a specific activity of 318 microCi.mmol(-1); if however the amount was supplied in aliquots over 4 days a specific activity of only 53.1 microCi.mmol(-1) Xn was obtained.     

A safety study of oral xanthohumol administration and its influence on fertility in Sprague Dawley rats

Xanthohumol (XN) is a prenylated chalcone, which has been shown to possess a broad range of potential cancer preventive and additional biological activities. In the present study, we have determined the subchronic 4-wk toxicity of XN and monitored its influence on fertility and development of offspring in two fertility studies. Four-week-old female Sprague Dawley (SD) rats were treated with 0.5% XN in the diet or with 1,000 mg XN/kg body weight (b.w.) per day by gavage for 28 days. No remarkable treatment-related changes in general appearance and b.w. occurred during the study. After autopsy, liver, kidney, lung, heart, stomach, and spleen were examined macroscopically and histopathologically. Relative liver weights of animals in both treatment groups were significantly reduced by 30--40% in comparison with the control group, indicating weak hepatotoxicity. Also, mammary glands of treated rats appeared less developed compared to the controls. Consequently, we investigated the influence of XN on rat reproduction. In two fertility studies, XN (100 mg/kg b.w. per day), given either for 4 wk prior to or during mating, gestation, and nursing, did not cause any adverse effects on female reproduction and the development of offspring. Noteworthy, treatment of male rats prior to mating significantly (p=0.027) increased the sex ratio of male to female offspring. Overall, lifelong treatment at a daily dose of 100 mg/kg b.w. in a two-generation study did not affect the development of SD rats.     

Recovery and metabolism of xanthohumol in germ‐free and human microbiota‐associated rats

The impact of human intestinal bacteria on the bioavailability of the prenylflavonoid xanthohumol (XN) was studied by comparing germ‐free (GF) and human microbiota‐associated (HMA) rats. After XN application, XN, XN conjugates, and isoxanthohumol (IX) conjugates occurred in blood samples of GF and HMA rats, whereas IX was detected only in the blood of HMA rats. Overall excretion of XN and its metabolites within 48 h was only 4.6% of the ingested dose in GF rats and 4.2% in HMA rats, feces being the major route of excretion. While both GF and HMA rats excreted XN, IX, and their conjugates with urine and feces, 8‐prenylnaringenin and its corresponding conjugates were exclusively observed in the feces of HMA rats. The microbial formation of 8‐prenylnaringenin was confirmed by incubation of XN and IX with human fecal slurries. The amount of conjugates excreted in urine and feces was lower in HMA rats compared to GF rats indicating their hydrolysis by human intestinal microbiota. Thus, the impact of bacteria on the XN metabolism in the gut may affect the in vivo effects of ingested XN.     

Pharmacokinetic study of mangiferin in human plasma after oral administration

Mangiferin, an active component of traditional Chinese herbal medicine, although it is reported to have various pharmacological effects, the limited number of pharmacokinetic studies limit its wide application. To evaluate the pharmacokinetics of mangiferin in human, a sensitive high performance liquid chromatography-mass spectrometry (HPLC-MS) method for the determination of mangiferin in human plasma was developed. The proposed HPLC-MS method is selective, precise and accurate enough and enables the identification and quantification of mangiferin for the use in clinical studies. After single oral administration of 0.1, 0.3 and 0.9 g mangiferin, respectively, the method was successfully applied for the pharmacokinetics of mangiferin in 21 healthy male Chinese volunteers. The pharmacokinetic of mangiferin was fit to the non-compartmental model. The pharmacokinetics parameters were calculated. Mangiferin concentration in plasma reached 38.64 ± 6.75 ng/mL about 1 h after oral administration of 0.9 g mangiferin and the the apparent elimination half-life (t_1/2) was 7.85 ± 1.72 h. The absorption of mangiferin was increased with the administration of a large dose and it was concluded that the pharmacokinetics of mangiferin in human was nonlinear.     

In vitro phase II metabolism of xanthohumol by human UDP-glucuronosyltransferases and sulfotransferases

Xanthohumol (XN) is the principal prenylated flavonoid of the hop plant and has recently gained considerable interest due to its potential cancer-chemopreventive effects. However, the metabolism of XN has not yet been investigated in detail. Therefore, we studied the in vitro phase II metabolism of XN using nine human recombinant UDP-glucuronosyltransferases (UGT) and five sulfotransferases (SULT). The identification of the metabolites formed was elucidated using HPLC with diode array detection as well as HPLC/API-ES MS. XN was efficiently glucuronidated by UGT 1 A 8, 1 A 9, and 1 A 10; further important UGTs were UGT 1 A 1, 1 A 7, and 2 B 7. With respect to the sulfation reaction, SULT 1 A 1*2, 1 A 2, and 1 E 1 were the most active SULT forms. UGT 1 A 3, 1 A 4, and 1 A 6 as well as SULT 1 A 3 and 2 A 1 were of minor importance for the conjugation of XN. Three mono-glucuronides as well as three mono-sulfates were identified. Considering the tissue distribution of the tested UGT and SULT enzyme forms, these findings suggest a prominent role for the glucuronidation and sulfation of XN in the liver as well as in the gastrointestinal tract.     

Repeated oral administration modulates the pharmacokinetic behavior of the chemopreventive agent phenethyl isothiocyanate in rats

The principal objective of this study was to evaluate whether repeated oral administration influences the pharmacokinetic behavior of the chemopreventive agent phenethyl isothiocyanate (PEITC) in rat. Animals were treated orally with 0.5, 1.0 and 5.0 mg/kg of the isothiocyanate for 4 days, and plasma levels at various times post‐administration were determined by LC/MS after the first and last day. To determine absolute bioavailability, a group of animals was treated with a single (0.5 mg/kg) intravenous dose of PEITC. Following single oral dose administration, PEITC was rapidly absorbed, peak plasma concentrations being attained within the hour, and achieved an absolute bioavailability of 77%, but displayed dose‐dependent pharmacokinetics, with bioavailability decreasing and clearance increasing moderately with dose; C_max values did not rise proportionately to the dose and volume of distribution increased. At the higher doses of 1.0 and 5.0 mg/kg, repeated administration led to higher PEITC plasma C_max concentrations and decreased plasma clearance of the isothiocyanate leading to enhanced bioavailability.     

Urinary excretion of strawberry anthocyanins is dose dependent for physiological oral doses of fresh fruit

There is considerable interest in coloured fruits and berries as sources of biologically active anthocyanins. To examine the relationship between the oral dose and the amount excreted for anthocyanins from a food source across a physiological range of doses, volunteers were fed, in random order, four portions (100-400 g) of fresh strawberries as part of a standard breakfast. Urine was collected at 2 h intervals up to 8 h, and for the period 8-24 h. Fresh strawberries contained pelargonidin-3-glucoside as the major anthocyanin with smaller amounts of cyanidin-3-glucoside and pelargonidin-3-rutinoside. Anthocyanins were detected in the urine of all volunteers for all doses, predominantly as pelargonidin glucuronide and sulphate metabolites. There was a strong, linear relationship between oral dose and anthocyanin excretion (Pearson's product moment correlation coefficient = 0.692, p < 0.001, n = 40) which indicated that on an average, every additional unit of dose caused 0.0166 units of excretion. Within individuals, dose -- excretion data fitted a linear regression model (median R(2) = 0.93). We conclude that strawberry anthocyanins are partially bioavailable in humans with a linear relationship between oral dose and urinary excretion for doses up to 400 g fresh fruit.     

Pharmacokinetics and milk penetration of orbifloxacin after intravenous, subcutaneous, and intramuscular administration to lactating goats

The single-dose disposition kinetics of orbifloxacin were determined in clinically normal lactating goats (n = 6) after intravenous, subcutaneous, and intramuscular administration of 2.5 mg of orbifloxacin/kg of body weight. Orbifloxacin concentrations were determined by HPLC with fluorescence detection. The concentration-time data were analyzed by compartmental and noncompartmental kinetic methods. Steady-state volume of distribution and clearance of orbifloxacin after intravenous administration were 1.13 ± 0.08 L/kg and 0.40 ± 0.11 L/h·kg, respectively. Following subcutaneous and intramuscular administration, orbifloxacin achieved maximum plasma concentrations of 1.85 ± 0.20 and 1.66 ± 0.14 mg/L at 1.25 ± 0.22 and 0.87 ± 0.38 h, respectively. The absolute bioavailabilities after subcutaneous and intramuscular routes were 108.96 ± 17.61% and 105.01 ± 15.61%, respectively. Orbifloxacin penetration from the blood into the milk was rapid and showed high levels of concentrations in milk secretion. From this data, orbifloxacin could have success against susceptible mastitis pathogens in goats.     

Preparative isolation and purification of xanthohumol from hops (Humulus lupulus L.) by high-speed counter-current chromatography

Xanthohumol (XN) and related prenylflavonoids are the main bioactive components of hops (Humulus lupulus L.). The current work is to investigate the use of high-speed counter-current chromatography (HSCCC) in search for high isolation of xanthohumol from hops. A solvent system consisted of n-hexane-ethyl acetate-methanol-water at a volume ratio of 5:5:4:3 was employed. The results demonstrated that the constructed method could be well applied for the isolation of xanthohumol from hops extract. After HSCCC isolation procedure, the purity of xanthohumol was over 95% assayed by HPLC and the yield of extraction was 93.60%. The chemical structure identification of xanthohumol was carried out by UV, ¹H NMR and ¹³C NMR. The present results demonstrated that xanthohumol could be efficiently obtained using a single HSCCC step from H. lupulus L. extract.     

Profile of urinary and fecal proanthocyanidin metabolites from common cinnamon (Cinnamomum zeylanicum L.) in rats

Cinnamon (Cinnamomum zeylanicum L.) bark is widely used as a spice and in traditional medicine. Its oligomeric and polymeric proanthocyanidins are believed to be partly responsible for the beneficial properties of the plant. We describe here the metabolic fate of cinnamon proanthocyanidins in the urine and feces of rats fed a suspension of the whole bark. The metabolites include ten mono‐, di‐, and tri‐ conjugated (epi)catechin phase II metabolites and more than 20 small phenolic acids from intestinal microbial fermentation. Some of these are sulfated conjugates. Feces contain intact (epi)catechin and dimers. This suggests that free radical scavenging species are in contact with the intestinal walls for hours after ingestion of cinnamon. The phenolic metabolite profile of cinnamon bark in urine is consistent with a mixture of proanthocyanidins that are depolymerized into their constitutive (epi)catechin units as well as cleaved into smaller phenolic acids during their transit along the intestinal tract, with subsequent absorption and conjugation into bioavailable metabolites.     

Early indicators of kidney injury in male and female rats after oral administration of cadmium

The effect of cadmium on the urinary excretion of glucose, creatinine and enzymes has been studied in adult male and female rats given the substance (70, 140 and 280 mg/kg food) for 4 weeks. Renal function tests and gel electrophoresis of urinary proteins were conducted simultaneously. Sex-dependent differences were demonstrated with regard to sensitivity of several kidney parameters and their predictive character of a possible chronic nephrotoxicity. These results were compared with hematological and general biological examinations of cadmium toxicity.