Comparison of in vivo derived and scaled in vitro metabolic rate constants for several volatile organic compounds (VOCs).

Metabolic rate parameters estimation using in vitro data is necessary due to numbers of chemicals for which data are needed, trend towards minimizing laboratory animal use, and limited opportunity to collect data in human subjects. We evaluated how well metabolic rate parameters derived from in vitro data predict overall in vivo metabolism for a set of environmental chemicals for which well validated and established methods exist. We compared values of VmaxC derived from in vivo vapor uptake studies with estimates of VmaxC scaled up from in vitro hepatic microsomal metabolism studies for VOCs for which data were available in male F344 rats. For 6 of 7 VOCs, differences between the in vivo and scaled up in vitro VmaxC estimates were less than 2.6-fold. For bromodichloromethane (BDCM), the in vivo derived VmaxC was approximately 4.4-fold higher than the in vitro derived and scaled up VmaxC. The more rapid rate of BDCM metabolism estimated based in vivo studies suggests other factors such as extrahepatic metabolism, binding or other non-specific losses making a significant contribution to overall clearance. Systematic and reliable utilization of scaled up in vitro biotransformation rate parameters in PBPK models will require development of methods to predict cases in which extrahepatic metabolism and binding as well as other factors are likely to be significant contributors.

Metabolic Basis for Nonlinearity in 1,3-Dichloropropene Toxicokinetics and Use in Setting a Kinetically-derived Maximum Inhalation Exposure Concentration in Mice.

1,3-Dichloropropene (1,3-D) showed a statistically increased incidence of bronchioloalveolar adenomas in male B6C3F1 mice at 60 ppm air concentration during previous chronic inhalation testing. No tumors were observed in female mice, nor in either sex of F344 rats up to 60 ppm, the highest dose tested. Therefore, to understand if lung tumors observed in high dose male mice are due to saturation of metabolic clearance, the linearity of 1,3-D concentrations in mouse blood was investigated on day 15 of repeated nose-only inhalation exposure to 0, 10, 20, 40, 60, 90, and 120 ppm (6 h/d, 7 d/week). Additional groups were included at 20, 60, and 120 ppm for blood collection at 1.5 and 3 h of exposure and up to 25 or 40 min post-exposure to determine area-under-the-curve. The data provide multiple lines of evidence that systemic exposures to 1,3-D in the mouse become nonlinear at inhalation exposure levels of 30 ppm or above. A reduction in minute volume occurred at the highest exposure concentration. The glutathione (GSH)-dependent metabolism of 1,3-D results in significant depletion of GSH at repeated exposure levels of 30 ppm and above. This loss of GSH results in decreased metabolic clearance of this test material, with a concomitant increase of the 1,3-D isomers in circulating blood at exposure concentrations ≥30 ppm. Shifts in the ratio of cis- and trans-1,3-D also support nonlinear toxicokinetics well below 60 ppm. Based on this data, a kinetically derived maximum dose for 1,3-D in mice for repeated exposures should be at or below 30 ppm. These results support non-relevance of 1,3-D-induced benign pulmonary tumorigenicity in mice for human health risk assessment.

Toxic target of trans-crotonaldehyde in mitochondria altered by diallyl disulfides for anti-myocardial ischemia.

The purposes of this study were to probe spectral behaviors of the toxic targets in trans-crotonaldehyde (TCA) in mitochondria altered by diallyl disulfides (DADS) derived from garlic. Ultraviolet absorption spectra showed that when ethanol as a solvent, the DADS blue shifted the peak of TCA from 318 nm to 312 nm. In mitochondria, the DADS further blue displaced the peak of TCA from 312 nm to 308 nm. Raman spectra displayed that the SS of DADS directly interacted with the CC toxic target of TCA, then the CCC of DADS interacted with the CHO toxic target of TCA. When DADS to TCA was 1:2, the DADS was the most powerful for the removal of the CC and CHO toxic targets of TCA. Study suggested that the SS of DADS altered the CC toxic target of TCA, while the CCC of DADS eliminated the CHO toxic target of TCA via local electron delocalization. The above two together clearly depicted the spectral behaviors of the toxic targets of TCA in mitochondria altered by DADS. These results are of great significance and value to elucidate the effects of garlic organic polysulfide on myocardial ischemia for the extensive development and use of garlic extracts.

In situ self-spray coating system that can uniformly disperse a poorly water-soluble H2S donor on the colorectal surface to treat inflammatory bowel diseases.

Inflammatory bowel disease (IBD) is an intestinal inflammatory disorder. Exogenous hydrogen sulfide (H2S) donors such as diallyl trisulfide (DATS) have been used as anti-inflammatory mediators. However, an ideal method of administering DATS has yet to be established owing to its poor water solubility. Herein, a self-spray coating system that is derived from a DATS-loaded capsule with foaming capability (CAP-w-FC) is proposed for treating colitis. Following the rectal administration of CAP-w-FC into rats bearing colitis and its subsequent dissolution in the intestinal fluid, a spray coating system is self-assembled in situ. This system greatly promotes the dissolution of the poorly water-soluble DATS by producing nano-scaled micellar particles that are sprayed onto the large luminal surface of the colorectal tract. Following the internalization of the micellar particles by colon epithelial cells, their loaded DATS reacts with intracellular glutathione to yield H2S. This exogenous H2S then diffuses through plasma membranes to carry out its biological functions, including suppressing the overproduction of pro-inflammatory cytokines, inhibiting the adhesion of macrophages on the vascular endothelium, and repairing colonic inflamed tissues. Analytical results demonstrate that this self-spray coating system may be used as a unique drug delivery technique for covering the large colorectal surface to treat IBD.

Dietary Bioactive Diallyl Trisulfide in Cancer Prevention and Treatment.

Bioactive dietary agents have been shown to regulate multiple cancer hallmark pathways. Epidemiologic studies have linked consumption of Allium vegetables, such as garlic and onions, to decreased incidence of cancer. Diallyl trisulfide (DATS), a bioactive compound derived from Allium vegetables, has been investigated as an anti-cancer and chemopreventive agent. Preclinical studies provide ample evidence that DATS regulates multiple cancer hallmark pathways including cell cycle, apoptosis, angiogenesis, invasion, and metastasis. DATS has been shown to arrest cancer cells at multiple stages of the cell cycle with the G2/M arrest being the most widely reported. Additionally, increased pro-apoptotic capacity as a result of regulating intrinsic and extrinsic apoptotic pathway components has been widely reported following DATS treatment. Invasion, migration, and angiogenesis represent emerging targets of DATS and support its anti-cancer properties. This review summarizes DATS mechanisms of action as an anti-cancer and chemopreventive agent. These studies provide rationale for future investigation into its use as a cancer chemopreventive agent.

Pharmacokinetic analysis of thymol, carvacrol and diallyl disulfide after intramammary and topical applications in healthy organic dairy cattle.

Mastitis is among the most costly concerns for dairy producers whether cattle are managed conventionally or organically. Unfortunately, there are no USFDA-approved mastitis treatments that allow dairy cows in the United States to maintain organic dairy status. We investigated the plasma pharmacokinetics of three organic mastitis products currently used by organic producers and organic dairy veterinarians. Those products include intramammary, topical and intravaginal preparations, each dosed at two levels. Additionally, tissue data were collected for kidney, liver and fat in order to estimate a withholding time for each of the products. The lower limit of quantification (LOQ) and lower limit of detection (LOD) were 0.001 and 0.0005 µg ml-1, respectively, in plasma and all tissues except fat for both thymol and carvacrol. Fat had an LOQ of 0.01 µg ml-1 and an LOD of 0.005 µg ml-1 for thymol and carvacrol. Diallyl disulfide had an LOQ of 0.005 µg ml-1 and LOD of 0.001 µg ml-1 in all tissues. For diallyl disulfide (garlic), no levels above 0.001 µg ml-1 were measurable in plasma or tissues. For topical and intramammary products, levels were measurable in the plasma, liver, kidney and fat up to 72 h after the last dose. The plasma half-lives were short for thymol (approximately 1.6 h) and carvacrol (approximately 1.5 h), whereas the estimated half-lives for these substances in tissues ranged from 13.9 to 31.5 h for thymol and from 16.9 to 25 h for carvacrol. The predicted amount of time that the molecules would be found in the body based on the slowest depletion time of liver tissue was 13 days for thymol and 10 days for carvacrol. The apparent half-life of topically applied carvacrol was approximately 4.5 h in plasma, with an estimated withhold time of 10 days. These times were calculated using the USFDA's tolerance limit method for meat withdrawal times.

Antifungal activity, kinetics and molecular mechanism of action of garlic oil against Candida albicans.

The antifungal activity, kinetics, and molecular mechanism of action of garlic oil against Candida albicans were investigated in this study using multiple methods. Using the poisoned food technique, we determined that the minimum inhibitory concentration of garlic oil was 0.35 µg/mL. Observation by transmission electron microscopy indicated that garlic oil could penetrate the cellular membrane of C. albicans as well as the membranes of organelles such as the mitochondria, resulting in organelle destruction and ultimately cell death. RNA sequencing analysis showed that garlic oil induced differential expression of critical genes including those involved in oxidation-reduction processes, pathogenesis, and cellular response to drugs and starvation. Moreover, the differentially expressed genes were mainly clustered in 19 KEGG pathways, representing vital cellular processes such as oxidative phosphorylation, the spliceosome, the cell cycle, and protein processing in the endoplasmic reticulum. In addition, four upregulated proteins selected after two-dimensional fluorescence difference in gel electrophoresis (2D-DIGE) analysis were identified with high probability by mass spectrometry as putative cytoplasmic adenylate kinase, pyruvate decarboxylase, hexokinase, and heat shock proteins. This is suggestive of a C. albicans stress responses to garlic oil treatment. On the other hand, a large number of proteins were downregulated, leading to significant disruption of the normal metabolism and physical functions of C. albicans.

PXS-4681A, a potent and selective mechanism-based inhibitor of SSAO/VAP-1 with anti-inflammatory effects in vivo.

Semicarbazide-sensitive amine oxidase (SSAO), also known as vascular adhesion protein-1 (VAP-1), is a member of the copper-dependent amine oxidase family that is associated with various forms of inflammation and fibrosis. To investigate the therapeutic potential of SSAO/VAP-1 inhibition, potent and selective inhibitors with drug-like properties are required. PXS-4681A [(Z)-4-(2-(aminomethyl)-3-fluoroallyloxy)benzenesulfonamide hydrochloride] is a mechanism-based inhibitor of enzyme function with a pharmacokinetic and pharmacodynamic profile that ensures complete, long-lasting inhibition of the enzyme after a single low dose in vivo. PXS-4681A irreversibly inhibits the enzyme with an apparent Ki of 37 nM and a kinact of 0.26 min(-1) with no observed turnover in vitro. It is highly selective for SSAO/VAP-1 when profiled against related amine oxidases, ion channels, and seven-transmembrane domain receptors, and is superior to previously reported inhibitors. In mouse models of lung inflammation and localized inflammation, dosing of this molecule at 2 mg/kg attenuates neutrophil migration, tumor necrosis factor-α, and interleukin-6 levels. These results demonstrate the drug-like properties of PXS-4681A and its potential use in the treatment of inflammation.

Development, characterization and efficacy of niosomal diallyl disulfide in treatment of disseminated murine candidiasis.

In the current study, a novel niosome based formulation of diallyl disulfide (DADS) was evaluated for its potential to treat disseminated candidiasis in mouse model. Among various non-ionic surfactants tested, niosome formulation prepared using Span 80 was found to be most efficient in the entrapment of DADS. The DADS loaded niosomes had size dimensions in the range of 140 ± 30 nm with zeta potential of -30.67 ± 4.5. Liver/kidney function tests as well as histopathologic studies suggested that noisome-based DADS formulations are safe at the dose investigated. When administered to Candida albicans infected animals, the DADS bearing niosomal formulation cleared the fungal burden and increased their survival much efficiently than its free form. FROM THE CLINICAL EDITOR: In this study, a novel niosomal formulation of the antifungal DADS was utilized in a murine candidiasis model, resulting in more efficient fungal clearance compared to the free formulation.

The discovery and development of selective 3-fluoro-4-aryloxyallylamine inhibitors of the amine oxidase activity of semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1).

A new class of 3-fluoroallyl amine-based SSAO/VAP-1 inhibitors is reported. These compounds have excellent selectivity over diamine oxidase, MAO-A and MAO-B. Synthesis and SAR studies leading to compound 28 (PXS-4159A) are reported. The pharmacokinetic profile of 28 in the rat, together with activity in a murine model of lung inflammation are also disclosed.

An oil-free microemulsion for intravenous delivery of diallyl trisulfide: formulation and evaluation.

The aim of the present study was to develop an oil-free o/w microemulsion, Cremophor EL:ethanol-propylene glycol:saline, for diallyl trisulfide (DATS) for intravenous (i.v.) administration to modify the safety and pharmacokinetics of DATS. The ternary diagram was constructed to identify the regions of dilutable microemulsions, and the optimal composition of microemulsion was determined by evaluation of injection safety such as hemolysis, intravenous stimulation and injection anaphylaxis compared to commercial formulation Chentian(®). Promising microemulsion with modified injection safety was developed that could incorporate 100 mg/g of DATS. The droplet size of the microemulsion was about 26 nm in diameter with narrow distribution (polydispersity index: 0.14). Acute toxicity test showed that median lethal dose (LD(50)) of DATS microemulsion was 1.69-fold higher than that of Chentian(®). Pharmacokinetics was assessed by comparing with the commercial injection after intravenous administration to rats at a dose of 30 mg/kg. The developed microemulsion showed significant higher area under the drug concentration-time curve and lower clearance and distribution volume than those of Chentian(®) (p<0.05). This helped DATS to reach higher level in vessel, and circulate in the blood stream for a longer time resulting in better therapeutic effect. In conclusion, microemulsion would be a promising intravenous delivery system for DATS.

Negligible effect of oral garlic oil on the oral absorption of pyridoxine in metadoxine in rats.

Metadoxine [an ion-pair between pyridoxine and pyrrolidone carboxylate (PCA)] plus garlic oil treatment synergistically reduces alcoholic steatosis compared to each agent alone. We evaluated the effect of garlic oil on the pharmacokinetics of pyridoxine. After the oral administration of metadoxine, the total area under the plasma concentration-time curve from time zero to time infinity (AUC) and the peak plasma concentration (C(max)) of pyridoxine were significantly greater (by 40.6%) and higher (by 63.9%), respectively, than after oral administration of pyridoxine plus PCA. Oral metadoxine plus garlic oil also gave larger AUC (31.8%) and higher C(max) (64.9%) than pyridoxine plus PCA. However, garlic oil did not change the AUC or C(max) of pyridoxine in metadoxine. Thus, garlic oil does not enhance the metadoxine activity by affecting the absorption of pyridoxine.

Efficacy of niosomal formulation of diallyl sulfide against experimental candidiasis in Swiss albino mice.

AIM: We developed a niosomal formulation of diallyl sulfide (DAS), a garlic oil component, and evaluated its efficacy against experimental candidiasis in mice. METHODS: DAS-bearing niosomes prepared from sorbitan monoester surfactants were evaluated for drug entrapment efficiency, release kinetics, toxicity, size, zeta-potential and others. Mice challenged with Candida albicans were treated with various DAS formulations. The efficacy of the formulations was assessed on the basis of reduction in mortality and decrease in residual fungal load in vital organs, such as liver and spleen, of treated mice. RESULTS: Niosomal DAS (12 mg/kg body weight) significantly reduced fungal load and mortality in treated animals compared with the free form of DAS. Niosomal DAS was also found to be free of toxic manifestations, as revealed by histopathological studies, as well as liver/kidney function tests. CONCLUSION: Incorporation of DAS in niosomes enhances its antifungal efficacy. Further studies are needed to optimize the current findings to develop an efficient nature-derived alternative antifungal therapeutic strategy.

[Tissue distribution of solid lipid nanoparticles loaded garlic oil in rats].

OBJECTIVE: To investigate the tissue distribution of the diallyl disulfide (DADS) and diallyl trisulfide (DATS) in solid lipid nanoparticles loaded garlic oil (GO-SLN) in rats. METHOD: The gas chromatography-electron capture detection (GC-ECD) method was established to determined the DADS and DATS simultaneously in the biological samples of rats after administration of 0.5 mL garlic oil injection or GO-SLN (containing about 10 mg garlic oil) via jugular vein cannula. The conditions for gas chromatographic separation were as follows. The oven temperature was set at 110 degrees C and maintained for 15 min. Temperatures at the injection port and detector were 180 degrees C and 300 degrees C, respectively. Ultra-pure nitrogen (purity > 99.999%, Shenyang Kerui Special Gases Co. Ltd., China) was used as a carrier gas and made-up gas at flow-rates of 1 mL x min(-1) and 60 mL x min(-1), respectively. All injections were carried out in the split injection mode with a split ratio of 1:10. RESULT: The GC-ECD method was fit for determing the concentration of DADS and DATS in garlic oil. The distribution character of GO-SLN in rats had changed to some extent and the concentration of GO-SLN in tissues was higher than that of GO-Injection. CONCLUSION: The SLN can elevate the passive targeting of drugs and lengthen their action time in tissues.

Fragrance material review on allyl cinnamate.

A toxicologic and dermatologic review of allyl cinnamate when used as a fragrance ingredient is presented.

Fragrance material review on allyl alpha-ionone.

A toxicologic and dermatologic review of allyl alpha-ionone when used as a fragrance ingredient is presented.

Identification and synthesis of a novel selective partial PPARdelta agonist with full efficacy on lipid metabolism in vitro and in vivo.

The aim was to identify a novel selective PPARdelta agonist with full efficacy on free fatty acid (FFA) oxidation in vitro and plasma lipid correction in vivo. Using the triple PPARalpha,gamma,delta agonist 1 as the structural starting point, we wanted to investigate the possibility of obtaining selective PPARdelta agonists by modifying only the acidic part of 1, while holding the lipophilic half of the molecule constant. The structure-activity relationship was guided by in vitro transactivation data using the human PPAR receptors, FFA oxidation efficacy performed in the rat muscle L6 cell line, and in vivo rat pharmacokinetic properties. Compound 7 ([4-[3,3-bis-(4-bromo-phenyl)-allylthio]-2-chloro-phenoxy]-acetic acid) was identified as a selective, partial agonist with good oral pharmacokinetic properties in rat. Chronic treatment of high fat fed ApoB100/CETP-Tgn mice with 7 corrected the plasma lipid parameters and improved insulin sensitivity. These data suggest that selective PPARdelta agonists have the potential to become a novel treatment of dyslipidemia.

Determination of the concentration of diallyl trisulfide in rat whole blood using gas chromatography with electron-capture detection and identification of its major metabolite with gas chromatography mass spectrometry.

A simple, rapid, and sensitive procedure has been developed using gas chromatography with electron-capture detection to measure diallyl trisulfide levels in rat blood. Blood samples were acidified, and the analyte was extracted with hexane, and then degradation was stopped with acetonitrile before gas chromatographic separation. Two calibration curves were linear over the range of 10-500 ng/ml and 0.2-20 microg/ml, with typical r values of 0.9986 and 0.9993, respectively. The structure of its major metabolite was confirmed using combined gas chromatography-mass spectrometry. The limit of detection was less than 10 ng/ml, and the assay was highly reproducible, giving peaks with excellent chromatographic properties. The method is suitable for pharmacokinetic and therapeutic purposes.

Simultaneous determination of diallyl trisulfide and diallyl disulfide in rat blood by gas chromatography with electron-capture detection.

A simple, rapid and sensitive method has been developed and validated for the simultaneous quantification of diallyl trisulfide (DATS) and diallyl disulfide (DADS) in rat blood by gas chromatography with electron-capture detection. The analytes were prevented from degradation by addition of acetonitrile and extraction with hexane before gas chromatographic separation. Two calibration curves for DATS were linear over the range of 10-500 ng/mL and 0.2-20 microg/mL, with typical r values of 0.9989 and 0.9993, respectively. Similarly, two calibration curves for DADS were linear in the concentration range of 50-5000 ng/mL and 1-30 microg/mL, with typical r values of 0.9989 and 0.9983, respectively. The limit of detection was less than 10 ng/mL for DATS and 50 ng/mL for DADS, and the assay was highly reproducible, considering the intra-, inter-day relative standard deviations (R.S.D.) below 12%. The developed procedure was successfully applied for the evaluation of the pharmacokinetics of garlic oil following iv administration at a single dose (10 mg) of garlic oil in rats. The results show that the developed method is suitable for pharmacokinetic and therapeutic purposes of DATS and DADS.

Composition, stability, and bioavailability of garlic products used in a clinical trial.

In support of a new clinical trial designed to compare the effects of crushed fresh garlic and two types of garlic supplement tablets (enteric-coated dried fresh garlic and dried aged garlic extract) on serum lipids, the three garlic products have been characterized for (a) composition (14 sulfur and 2 non-sulfur compounds), (b) stability of suspected active compounds, and (c) availability of allyl thiosulfinates (mainly allicin) under both simulated gastrointestinal (tablet dissolution) conditions and in vivo. The allyl thiosulfinates of blended fresh garlic were stable for at least 2 years when stored at -80 degrees C. The dissolution release of thiosulfinates from the enteric-coated garlic tablets was found to be >95%. The bioavailability of allyl thiosulfinates from these tablets, measured as breath allyl methyl sulfide, was found to be complete and equivalent to that of crushed fresh garlic. S-Allylcysteine was stable for 12 months at ambient temperature. The stability of the suspected active compounds under the conditions of the study and the bioavailability of allyl thiosulfinates from the dried garlic supplement have validated the use of these preparations for comparison in a clinical trial.