3-Allyltrisulfanyl-alanine Formation during the Preparation of Aged Garlic Extract.

The formation of 3-allyltrisulfanyl-alanine (ATrSA) was investigated during the aging process to prepare aged garlic extract (AGE). In raw garlic, ATrSA and its possible precursor, S-allylmercaptocysteine (SAMC), were barely detectable. However, the ATrSA content in AGE increased steadily during the 22 month of aging, while the SAMC level increased to a maximum at 4 months and then gradually decreased. In a model reaction mimicking the AGE preparation process, ATrSA production was decreased when the formation of SAMC was blocked by a γ-glutamyl-transpeptidase inhibitor but its decrease was reversed by the addition of SAMC. We also found that ATrSA was formed by the incubation of SAMC with allylsulfides such as diallyldisulfide and diallyltrisulfide. These findings suggest that ATrSA is formed via the reaction involving SAMC during the aging process. In addition, we found that ATrSA inhibits the secretion of interleukin-6 induced by lipopolysaccharide in mouse splenic lymphocytes in culture.

Antimicrobial properties of hydrophobic compounds in garlic: Allicin, vinyldithiin, ajoene and diallyl polysulfides.

Allium plants, such as garlic, onion and leek have long been known to be effective in the therapy of infectious diseases. In particular, garlic has a greater antimicrobial activity than other Allium plants as it contains several hydrophobic antimicrobial compounds, such as allicin, vinyldithiins, ajoenes and diallyl polysulfides. Allicin is a characteristic sulfur-containing compound found in raw garlic produced from alliin and exhibits antimicrobial activity against both Gram-positive and Gram-negative bacteria. In addition, allicin has been reported to inhibit the biofilm formation of bacteria, which is a major cause of bacterial resistance to the antibiotic treatment of infections, by regulating quorum sensing in microorganisms. Other hydrophobic compounds also have similar inhibitory effects on bacteria as allicin. These biological properties of garlic-derived hydrophobic compounds can be used to enhance the effects of existing drugs and may thus be used in the treatment of infections, such as by preventing drug resistance through the inhibition of biofilm formation. In this review, we summarize the effects of hydrophobic compounds of garlic on bacteria.

Regulation of immune response by S-1-propenylcysteine through autophagy-mediated protein degradation.

Autophagy is a key event in cellular recycling processes due to its involvement in the intracellular degradation of proteins. It has been demonstrated that S-1-propenylcysteine (S1PC), a characteristic sulfur compound in aged garlic extract, induces the activation of autophagy. S1PC degrades the adaptor protein myeloid differentiation response protein 88 (MyD88) of downstream of Toll-like receptor (TLR) by activating autophagy in vitro and in vivo. The degradation of MyD88 inhibits the TLR signaling pathway, including the phosphorylation of interleukin 1 receptor associated kinase 4 (IRAK4) and nuclear factor (NF)-κB p65 in vitro, and eventually leads to the inhibition of interleukin (IL)-6 production in vitro and C-C motif chemokine ligand 2 (Ccl2) mRNA expression in vivo. S1PC also increases the level of intestinal immunoglobulin A (IgA) and the number of IgA-producing cells in Peyer's patches in vivo. In addition, S1PC triggers the mRNA expression of X-box binding protein 1 (Xbp1), an inducer of IgA-producing cell differentiation via the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and the degradation of paired box protein 5 (Pax5), a suppressor of Xbp1 mRNA expression. The present review summarizes the mechanisms through which the activation of autophagy by S1PC modulates the immune response.

Chemistry of aged garlic: Diversity of constituents in aged garlic extract and their production mechanisms via the combination of chemical and enzymatic reactions.

Raw garlic contains characteristic compounds, such as S-alk(en)ylcysteine sulfoxides, γ-glutamyl-S-alk(en)-ylcysteines and polysaccharides. These compounds undergo various transformation processes during the aging process. Among these compounds, the change of sulfur-containing molecules is diverse and time-dependent. Previously, by means of the liquid chromatography (LC)/LC-mass spectrometry (MS) method, a number of unidentified peaks corresponding to candidates of sulfur-containing molecules were detected in the chromatogram of aged garlic extract (AGE), and identified using MS and nuclear magnetic resonance (NMR). The production mechanisms of these compounds were then examined by model reactions and laboratory experiments mimicking the aging process. Three γ-glutamyl tripeptides [γ-glutamyl-γ-glutamyl-S-methylcysteine, γ-glutamyl-γ-gluta-myl-S-allylcysteine (GGSAC), γ-glutamyl-γ-glutamyl-S-1-propenylcysteine], γ-glutamyl-S-allylmercaptocysteine (GSAMC) and cis-S-1-propenylcysteine (cis-S1PC) were isolated and identified. GGSAC was produced from GSAC through the enzymatic reaction catalyzed by γ-glutamyltranspeptidase (GGT), and two other tripeptides could be produced in similar reactions. GSAMC was produced by the reaction between γ-glutamyl dipeptides and allicin. Furthermore, GSAMC was a precursor compound of S-allyl-mercaptocysteine (SAMC), and thus it was produced from GSAMC by GGT. cis-S1PC was produced from trans-S1PC by the isomerization reaction. A number of other compounds were also identified, including Maillard reaction products; however, their production mechanisms have not been elucidated. In this review, we present the changes in characteristic constituents in raw garlic and garlic extract during the aging process and discuss their production mechanisms involving the various chemical and enzymatic reactions.

Changes of S-Allylmercaptocysteine and γ-Glutamyl- S-allylmercaptocysteine Contents and Their Putative Production Mechanisms in Garlic Extract during the Aging Process.

γ-Glutamyl- S-allylmercaptocysteine (GSAMC), a putative precursor compound of S-allylmercaptocysteine (SAMC), was isolated and identified from aged garlic extract (AGE). We analyzed the change of their contents in AGE during the aging process, chronologically from 1 to 22 months. The formation of these compounds occurred mostly during the early stage of the aging period: the SAMC content reached a maximum at approximately 4 months, whereas the GSAMC content reached a maximum at 1 month and then decreased during the subsequent aging period. To assess the possible relationship between the change of the two compounds during the aging process, we set up the model reactions with the hypothesis that GSAMC is produced from γ-glutamyl- S-allylcysteine (GSAC)/γ-gultamyl- S-1-propenylcysteine (GS1PC) and that SAMC is produced from GSAMC by endogenous γ-glutamyl transpeptidase (GGT) in garlic during the early stage of the aging process. We found that, in the model reactions, SAMC was produced from GSAMC by the garlic protein fraction having GGT activity and its production was suppressed by a GGT inhibitor. Furthermore, the production of GSAMC from allicin and GSAC/GS1PC was found in another model reaction. The reaction between allicin and GS1PC was faster than that between allicin and GSAC and, thus, may be involved in the production of GSAMC in the early stage of the aging process.

Anti-inflammatory action of cysteine derivative S-1-propenylcysteine by inducing MyD88 degradation.

The degradation of target proteins by small molecules utilizing the cellular proteolytic system is featured as a treatment strategy of several diseases. We found that S-1-propenylcysteine (S1PC) among several cysteine derivatives in aged garlic extract inhibited TLR-mediated IL-6 production by inducing the degradation of adaptor protein MyD88. We showed that S1PC directly denatured MyD88 and induced the formation of protein aggregates. Consequently, MyD88 was degraded by aggresome-autophagy pathway. On the other hand, S-allylcysteine, a structural analog of S1PC, failed to induce the degradation of MyD88 because of its inability to denature MyD88 although it also activated autophagy. Our findings suggest that S1PC induces MyD88 degradation through the denaturation of MyD88 and the activation of autophagy. Thus, S1PC may serve as the base to develop a therapeutic means for immune diseases associated with aberrant TLR signaling pathways.

Isolation and Identification of Three γ-Glutamyl Tripeptides and Their Putative Production Mechanism in Aged Garlic Extract.

We analyzed aged garlic extract (AGE) to understand its complex sulfur chemistry using post-column high-performance liquid chromatography with an iodoplatinate reagent and liquid chromatography high resolution mass spectrometry (LC-MS). We observed unidentified peaks of putative sulfur compounds. Three compounds were isolated and identified as γ-glutamyl-γ-glutamyl- S-methylcysteine, γ-glutamyl-γ-glutamyl- S-allylcysteine (GGSAC) and γ-glutamyl-γ-glutamyl- S-1-propenyl-cysteine (GGS1PC) by nuclear magnetic resonance and LC-MS analysis based on comparisons with chemically synthesized reference compounds. GGSAC and GGS1PC were novel compounds. Trace amounts of these compounds were detected in raw garlic, but the contents of these compounds increased during the aging process. Production of these compounds was inhibited using a γ-glutamyl transpeptidase (GGT) inhibitor in the model reaction mixtures. These findings suggest that γ-glutamyl tripeptides in AGE are produced by GGT during the aging process.

Effects of S-1-propenylcysteine, a sulfur compound in aged garlic extract, on blood pressure and peripheral circulation in spontaneously hypertensive rats.

OBJECTIVES: This study was designed to investigate the antihypertensive effect of S-1-propenylcysteine, a characteristic sulfur compound in aged garlic extract, using a hypertensive rat model. METHODS: The blood pressure and tail blood flow of both spontaneously hypertensive rats and control Wistar Kyoto rats were measured by the tail-cuff method and the noncontact laser Doppler method, respectively, at various times after single oral administration of a test compound for 24 h. KEY FINDINGS: Treatment with S-1-propenylcysteine (6.5 mg/kg BW) significantly decreased the systolic blood pressure of spontaneously hypertensive rat approximately 10% at 3 h after administration, and thereafter, the systolic blood pressure gradually returned to the baseline level in 24 h. The effect of S-1-propenylcysteine was dose-dependent and was maximal at the dose of 6.5 mg/kg BW at 3 h. However, the other compounds such as S-allylcysteine and S-allylmercaptocysteine in aged garlic extract were ineffective. In addition, S-1-propenylcysteine had no effect on systolic blood pressure of control Wistar Kyoto rats. Furthermore, S-1-propenylcysteine significantly increased the blood flow at 3 h after administration at the dose of 6.5 mg/kg BW. CONCLUSIONS: S-1-propenylcysteine is a key constituent of aged garlic extract responsible for its antihypertensive effect, and the effect of S-1-propenylcysteine involves the improvement in peripheral circulation.

Metabolomic study on the antihypertensive effect of S-1-propenylcysteine in spontaneously hypertensive rats using liquid chromatography coupled with quadrupole-Orbitrap mass spectrometry.

Aged garlic extract (AGE) has been shown to improve hypertension in both clinical trials and experimental animal models. However, the active ingredient of AGE remains unknown. In the present study, we investigated the antihypertensive effects of AGE and its major constituents including S-1-propenylcysteine (S1PC) and S-allylcysteine (SAC) using spontaneously hypertensive rats (SHR) and found that S1PC is an active substance to lower blood pressure in SHR. In addition, the metabolomics approach was used to investigate the potential mechanism of the antihypertensive action of S1PC in SHR. Treatment with AGE (2g/kg body weight) or S1PC (6.5mg/kg body weight; equivalent to AGE 2g/kg body weight) significantly decreased the systolic blood pressure (SBP) of SHR after the repeated administration for 10 weeks, whereas treatment with SAC (7.9mg/kg body weight; equivalent to AGE 2g/kg body weight) did not decrease the SBP. After the treatment for 10 weeks, the plasma samples obtained from Wistar Kyoto (WKY) rats and SHR were analyzed by means of ultra high performance liquid chromatography coupled with high-resolution quadrupole-Orbitrap mass spectrometry. Multivariate statistical analysis of LC-MS data showed a clear difference in the metabolite profiles between WKY rats and SHR. The results indicated that 30 endogenous metabolites significantly contributed to the difference and 7 of 30 metabolites were changed by the S1PC treatment. Furthermore, regression analysis showed correlation between SBP and the plasma levels of betaine, tryptophan and 3 LysoPCs. This metabolomics approach suggested that S1PC could exert its antihypertensive effect by affecting glycine, serine and threonine metabolism, tryptophan metabolism and glycerophospholipid metabolism.

Aged garlic extract exerts endothelium-dependent vasorelaxant effect on rat aorta by increasing nitric oxide production.

BACKGROUND: Clinical trials have shown that aged garlic extract (AGE) is effective in reducing blood pressure of hypertensive patients. However, the mechanisms involved remain to be elucidated. PURPOSE: The aim of the present study was to investigate the vasorelaxant effect of AGE on the aorta and its mechanism of action in order to clarify the blood pressure-lowering action of AGE. METHODS: The vasorelaxant effect was evaluated in isolated rat aortic rings. After aortic rings were contracted by 3 × 10-6M norepinephrine (NE) for 30min, AGE and other test drugs were added to the aortic rings. All results were expressed as percentages of the maximal NE-induced contraction. RESULTS: AGE induced the concentration-dependent vasorelaxation of isolated rat aortic rings that had been precontracted with norepinephrine. The effect of AGE was severely impaired in aortic rings lacking endothelium. In addition, the effect of AGE was inhibited by a nitric oxide synthase (NOS) inhibitor and a nitric oxide (NO) scavenger. Moreover, AGE treatment of aorta significantly increased the NO production. When various constituents of AGE were tested, the vasorelaxation of aorta was observed only in the presence of L-arginine, a substrate of NOS. CONCLUSION: AGE causes endothelium-dependent vasorelaxation of aorta via stimulation of NO production and that L-arginine in AGE serves as a key agent for NOS-mediated NO production.

S-1-Propenylcysteine promotes the differentiation of B cells into IgA-producing cells by the induction of Erk1/2-dependent Xbp1 expression in Peyer's patches.

OBJECTIVES: S-Allylcysteine (SAC) and S-1-propenylcysteine (S1PC) are the characteristic sulfur-containing amino acids in aged garlic extract. In this study, we investigated the effect of SAC and S1PC on intestinal immunoglobulin (Ig)A production to gain insight into the immunomodulatory effect of aged garlic extract. METHODS: In vitro study: Mouse splenic lymphocytes were treated with S1PC (0.1 and 0.3 mM) or SAC (0.1 and 0.3 mM) for 3 d, and IgA concentration in the culture medium was examined. In vivo study: Mice were orally administrated S1PC (7.5, 15, and 30 mg/kg) for 5 d and the IgA level in the intestinal lavage fluids as well as the population of IgA-producing cells in Peyer's patches were measured using mouse IgA enzyme-linked immunosorbent assay quantification set and flow cytometer, respectively. RESULTS: S1PC enhanced IgA production in mouse splenic lymphocytes in culture. However, SAC was ineffective. In addition, oral administration of S1PC to mice increased the IgA level and number of IgA-producing cells in Peyer's Patches. Furthermore, S1PC induced the expression of X-box binding protein 1 (Xbp1) mRNA, an inducer of plasma cell differentiation, in Peyer's patches. This induction was accompanied by the degradation of paired box protein 5 and the activation of mitogen activated protein/extracellular signal-regulated kinase signaling pathway. CONCLUSION: These results suggest that S1PC increases IgA-producing cells via the enhancement of Erk1/2-mediated Xbp1 expression in the intestine.

Natural thioallyl compounds increase oxidative stress resistance and lifespan in Caenorhabditis elegans by modulating SKN-1/Nrf.

Identification of biologically active natural compounds that promote health and longevity, and understanding how they act, will provide insights into aging and metabolism, and strategies for developing agents that prevent chronic disease. The garlic-derived thioallyl compounds S-allylcysteine (SAC) and S-allylmercaptocysteine (SAMC) have been shown to have multiple biological activities. Here we show that SAC and SAMC increase lifespan and stress resistance in Caenorhabditis elegans and reduce accumulation of reactive oxygen species (ROS). These compounds do not appear to activate DAF-16 (FOXO orthologue) or mimic dietary restriction (DR) effects, but selectively induce SKN-1 (Nrf1/2/3 orthologue) targets involved in oxidative stress defense. Interestingly, their treatments do not facilitate SKN-1 nuclear accumulation, but slightly increased intracellular SKN-1 levels. Our data also indicate that thioallyl structure and the number of sulfur atoms are important for SKN-1 target induction. Our results indicate that SAC and SAMC may serve as potential agents that slow aging.

Development of an Analytic Method for Sulfur Compounds in Aged Garlic Extract with the Use of a Postcolumn High Performance Liquid Chromatography Method with Sulfur-Specific Detection.

BACKGROUND: Garlic and its processed preparations contain numerous sulfur compounds that are difficult to analyze in a single run using HPLC. OBJECTIVE: The aim of this study was to develop a rapid and convenient sulfur-specific HPLC method to analyze sulfur compounds in aged garlic extract (AGE). METHODS: We modified a conventional postcolumn HPLC method by employing a hexaiodoplatinate reagent. Identification and structural analysis of sulfur compounds were conducted by LC-mass spectrometry (LC-MS) and nuclear magnetic resonance. The production mechanisms of cis-S-1-propenylcysteine (cis-S1PC) and S-allylmercaptocysteine (SAMC) were examined by model reactions. RESULTS: Our method has the following advantages: less interference from nonsulfur compounds, high sensitivity, good correlation coefficients (r > 0.98), and high resolution that can separate >20 sulfur compounds, including several isomers, in garlic preparations in a single run. This method was adapted for LC-MS analysis. We identified cis-S1PC and γ-glutamyl-S-allyl-mercaptocysteine in AGE. The results of model reactions suggest that cis-S1PC is produced from trans-S1PC through an isomerization reaction and that SAMC is produced by a reaction involving S-allylcysteine/S1PC and diallyldisulfide during the aging period. CONCLUSION: We developed a rapid postcolumn HPLC method for both qualitative and quantitative analyses of sulfur compounds, and this method helped elucidate a potential mechanism of cis-S1PC and SAMC action in AGE.

Metabolism, excretion, and pharmacokinetics of S-allyl-L-cysteine in rats and dogs.

The metabolism, excretion, and pharmacokinetics of S-allyl-l-cysteine (SAC), an active key component of garlic supplements, were examined in rats and dogs. A single dose of SAC was administered orally or i.v. to rats (5 mg/kg) and dogs (2 mg/kg). SAC was well absorbed (bioavailability >90%) and its four metabolites-N-acetyl-S-allyl-l-cysteine (NAc-SAC), N-acetyl-S-allyl-l-cysteine sulfoxide (NAc-SACS), S-allyl-l-cysteine sulfoxide (SACS), and l-γ-glutamyl-S-allyl-l-cysteine-were identified in the plasma and/or urine. Renal clearance values (<0.01 l/h/kg) of SAC indicated its extensive renal reabsorption, which contributed to the long elimination half-life of SAC, especially in dogs (12 hours). The metabolism of SAC to NAc-SAC, principal metabolite of SAC, was studied in vitro and in vivo. Liver and kidney S9 fractions of rats and dogs catalyzed both N-acetylation of SAC and deacetylation of NAc-SAC. After i.v. administration of NAc-SAC, SAC appeared in the plasma and its concentration declined in parallel with that of NAc-SAC. These results suggest that the rate and extent of the formation of NAc-SAC are determined by the N-acetylation and deacetylation activities of liver and kidney. Also, NAc-SACS was detected in the plasma after i.v. administration of either NAc-SAC or SACS, suggesting that NAc-SACS could be formed via both N-acetylation of SACS and S-oxidation of NAc-SAC. In conclusion, this study demonstrated that the pharmacokinetics of SAC in rats and dogs is characterized by its high oral bioavailability, N-acetylation and S-oxidation metabolism, and extensive renal reabsorption, indicating the critical roles of liver and kidney in the elimination of SAC.

Murine metabolism and absorption of lancemaside A, an active compound in the roots of Codonopsis lanceolata.

Lancemaside A, a triterpenoid saponin isolated from the roots of Codonopsis lanceolata, has been reported to ameliorate the reduction of blood testosterone levels induced by immobilization stress in mice. In the present study, we investigated the metabolism and absorption of lancemaside A in mice. After oral administration of lancemaside A at 100 mg/kg body weight, the unmetabolized compound appeared rapidly in plasma (t (max) = 0.5 h). Lancemaside A has a low bioavailability (1.1%) because of its metabolism by intestinal bacteria and its poor absorption in the gastrointestinal tract. Furthermore, we identified four metabolites from the cecum of mice after oral administration of lancemaside A: codonolaside II, echinocystic acid, echinocystic acid 28-O-beta-D: -xylopyranosyl-(1 --> 4)-alpha-L: -rhamnopyranosyl-(1 --> 2)-alpha-L: -arabinopyranosyl ester, and echinocystic acid 28-O-alpha-L: -rhamnopyranosyl-(1 --> 2)-alpha-L: -arabinopyranosyl ester. Among these metabolites, codonolaside II and echinocystic acid were detected in plasma, and their t (max) values were 4 and 8 h, respectively. These findings should be helpful for understanding the mechanism of the biological effect of lancemaside A.

Simultaneous determination of seven saponins in the roots of Codonopsis lanceolata by liquid chromatography-mass spectrometry.

We developed a rapid and simple analytical method for the simultaneous determination of seven 3,28-bidesmosidic triterpenoid saponins in the roots of Codonopsis lanceolata. The saponins are lancemaside A, lancemaside B, lancemaside C, lancemaside E, lancemaside G, foetidissimoside A, and aster saponin Hb. Root samples were extracted with 50% methanol and prepared for analysis. Saponins were detected by reversed-phase high-performance liquid chromatography with electrospray ionization mass spectrometry, and ginsenoside Rb(1) was used as an internal standard. The overall recoveries of all saponins were 92-116%, and the relative standard deviation values of intra- and inter-day precision were lower than 3.7 and 7.7%, respectively. Eight root samples collected from Korea and Japan were analyzed using the developed method. Lancemaside A was the most abundant saponin in the root samples from Korea, ranging from 2.65 to 3.64 mg/g dry root. However, the maximum content of lancemaside A among Japanese samples was 0.101 mg/g dry root.

Rapid identification of triterpenoid saponins in the roots of Codonopsis lanceolata by liquid chromatography-mass spectrometry.

Liquid chromatography coupled with sequential mass spectrometry (LC-MS(n)) has been used to identify 3,28-bidesmosidic triterpenoid saponins, lancemaside A (1), foetidissimoside A (2), aster saponin Hb (3), lancemaside E (4), lancemaside B (5), lancemaside F (6), lancemaside G (7), lancemaside C (8), and lancemaside D (9) in the roots of Codonopsis lanceolata. Structural information about both the aglycone and the sugar moiety at the C-3 position of saponins was obtained in the negative-ion mode. On the other hand, positive-ion spectra mainly provide structural information about the sugar chains of saponins, especially the oligosaccharide moiety at the C-28 position. During subsequent fragmentation of the product ions derived from the oligosaccharide moiety at the C-28 position, fragments produced by sequential loss of a monosaccharide unit were observed. Furthermore, the structural features of two unknown saponins in the roots of C. lanceolata were assigned on the basis of the fragmentation patterns of the known saponins. These studies demonstrate that LC-MS(n) analysis has great potential for the identification and characterization of triterpenoid saponins in plant extracts.

Pharmacokinetics of cycloalliin, an organosulfur compound found in garlic and onion, in rats.

Cycloalliin, an organosulfur compound found in garlic and onion, has been reported to exert several biological activities and also to remain stable during storage and processing. In this study, we investigated the pharmacokinetics of cycloalliin in rats after intravenous or oral administration. Cycloalliin and its metabolite, (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid, in plasma, urine, feces, and organs was determined by a validated liquid chromatography-mass spectrometry method. When administered intravenously at 50 mg/kg, cycloalliin was rapidly eliminated from blood and excreted into urine, and its total recovery in urine was 97.8% +/- 1.3% in 48 h. After oral administration, cycloalliin appeared rapidly in plasma, with a tmax of 0.47 +/- 0.03 h at 25 mg/kg and 0.67 +/- 0.14 h at 50 mg/kg. Orally administered cycloalliin was distributed in heart, lung, liver, spleen, and especially kidney. The Cmax and AUC0-inf values of cycloalliin at 50 mg/kg were approximately 5 times those at 25 mg/kg. When administered orally at 50 mg/kg, cycloalliin was excreted into urine (17.6% +/- 4.2%) but not feces. However, the total fecal excretion of (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid was 67.3% +/- 5.9% (value corrected for cycloalliin equivalents). In addition, no (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid was detected in plasma (<0.1 microg/mL), and negligible amounts (1.0% +/- 0.3%) were excreted into urine. In in vitro experiments, cycloalliin was reduced to (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid during anaerobic incubation with cecal contents of rats. These data indicated that the low bioavailability (3.73% and 9.65% at 25 and 50 mg/kg, respectively) of cycloalliin was due mainly to reduction to (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid by the intestinal flora and also poor absorption in the upper gastrointestinal tract. These findings are helpful for understanding the biological effects of cycloalliin.

Oral administration of a zinc complex improves type 2 diabetes and metabolic syndromes.

Previously, we reported that intraperitoneal injections of the Zn(II) complex (Zn(alx)(2)) with allixin, which is isolated from dry garlic, with a Zn(O(4)) coordination environment, exhibited high anti-diabetic effects in obesity-linked type 2 diabetic KKA(y) mice. However, this complex exhibited low activity when administered orally. To improve the effect of Zn(alx)(2), we prepared a novel Zn(II) complex with the allixin-derivative bis(1,6-dimethyl-3-hydroxy-5-methoxy-2-pentyl-1,4-dihydropyridine-4- thionato)Zn(II), abbreviated as Zn(II)-thioallixin-N-methyl (Zn(tanm)(2)), having a Zn(S(2)O(2)) coordination environment; this complex has extremely high in vitro insulin-like activity. Because Zn was extensively absorbed from the gastrointestinal tract when Zn(tanm)(2) was orally administered, its anti-diabetic effects were examined in KKA(y) mice. Daily oral administrations of Zn(tanm)(2) for 4 weeks in KKA(y) mice significantly improved hyperglycemia, glucose intolerance, insulin resistance, hyperleptinemia, obesity, and hypertension. Interestingly, Zn(tanm)(2) increased depressed plasma adiponectin levels in the mice. Here, we propose that Zn(tanm)(2) will be an orally active therapeutic for obesity-linked type 2 diabetes and metabolic syndromes.

Improvement of diabetes, obesity and hypertension in type 2 diabetic KKAy mice by bis(allixinato)oxovanadium(IV) complex.

Previously, we found that bis(allixinato)oxovanadium(IV) (VO(alx)(2)) exhibits a potent hypoglycemic activity in type 1-like diabetic mice. Since the enhancement of insulin sensitivity is involved in one of the mechanisms by which vanadium exerts its anti-diabetic effects, VO(alx)(2) was further tested in type 2 diabetes with low insulin sensitivity. The effect of oral administration of VO(alx)(2) was examined in obesity-linked type 2 diabetic KKA(y) mice. Treatment of VO(alx)(2) for 4 weeks normalized hyperglycemia, glucose intolerance, hyperinsulinemia, hypercholesterolemia and hypertension in KKA(y) mice; however, it had no effect on hypoadiponectinemia. VO(alx)(2) also improved hyperleptinemia, following attenuation of obesity in KKA(y) mice. This is the first example in which a vanadium compound improved leptin resistance in type 2 diabetes by oral administration. On the basis of these results, VO(alx)(2) is proposed to enhance not only insulin sensitivity but also leptin sensitivity, which in turn improves diabetes, obesity and hypertension in an obesity-linked type 2 diabetic animal.