S-allylcysteine scavenges singlet oxygen and hypochlorous acid and protects LLC-PK1 cells of potassium dichromate-induced toxicity

Advances in the study of vascular related protective effect of garlic (Allium sativum) extract and compounds

Garlic (Allium sativum) is a functional food containing multiple bioactive compounds that find widespread applications in culinary and medicinal practices. It consists of multiple chemical components, including allicin and alliin. This article offers a comprehensive review of the protective effects of garlic extracts and their active constituents on the vascular system. In vitro and in vivo experiments have shown that garlic extracts and their active ingredients possess various bioactive properties. These substances demonstrate beneficial effects on blood vessels by demonstrating anti-inflammatory and antioxidant activities, inhibiting lipid accumulation and migration, preventing lipid peroxidation, promoting angiogenesis, reducing platelet aggregation, enhancing endothelial function, and inhibiting endothelial cell apoptosis. In clinical studies, garlic and its extracts have demonstrated their efficacy in managing vascular system diseases, including atherosclerosis, diabetes, and high cholesterol levels. In summary, these studies highlight the potential therapeutic roles and underlying mechanisms of garlic and its constituents in managing conditions like diabetes, atherosclerosis, ischemic diseases, and other vascular disorders.

Elephant Black Garlic's Beneficial Properties for Hippocampal Neuronal Network, Chemical Characterization and Biological Evaluation

Garlic has been used for decades as an important food and additionally for its beneficial properties in terms of nutrition and ancestral therapeutics. In this work, we compare the properties of fresh (WG) and aged (BG) extract obtained from elephant garlic, harvested on Chiloe Island, Chile. BG was prepared from WG with a 20-day aging process under controlled temperature and humidity conditions. We observed that in BG, compounds such as diallyl disulfide decrease, and compounds of interest such as 5-hydroxymethylfurfural (69%), diallyl sulfide (17%), 3H-1,2-Dithiole (22%) and 4-Methyl-1,2,3-trithiolane (16%) were shown to be increased. Using 2,2-diphenyl-1-picrylhydrazyl (DPPH, BG: 51 ± 5.7%, WG: 12 ± 2.6%) and 2,20-azino-bis-(3-ethylbenzothiazoline-6 sulfonate) diammonium salt (ABTS, BG: 69.4 ± 2.3%, WG: 21 ± 3.9%) assays, we observed that BG possesses significantly higher antioxidant activity than WG and increased cell viability in hippocampal slices (41 ± 9%). The effects of WG and BG were shown to improve the neuronal function through an increased in intracellular calcium transients (189 ± 4%). In parallel, BG induced an increase in synaptic vesicle protein 2 (SV-2; 75 ± 12%) and brain-derived neurotrophic factor (BDNF; 32 ± 12%) levels. Thus, our study provides the initial scientific bases to foster the use of BG from Chiloe Island as a functional food containing a mixture of bioactive compounds that may contribute to brain health and well-being.

The Pharmacological Activity of Garlic (Allium sativum) in Parkinson's Disease: From Molecular Mechanisms to the Therapeutic Potential

Parkinson's disease (PD), one of the most common neurological diseases worldwide, is mainly characterized neuropathologically by the dopaminergic neurodegeneration in the substantia nigra pars compacta of the brainstem. Genetic and environmental factors contribute to PD pathophysiology through modulation of pleiotropic cellular mechanisms. The currently available treatment options focus only on replenishing dopamine and do not alter disease progression. Interestingly, garlic (Allium sativum), globally famed for its flavor and taste-enhancing properties, has shown protective activity in different PD models. Numerous chemical constituents of garlic, mainly the organosulfur compounds, have been shown to exhibit anti-Parkinsonian effects by targeting oxidative stress, mitochondrial impairment, and neuroinflammation-related signaling. However, despite its therapeutic potential against PD, the major bioactive components of garlic display some stability issues and some adverse effects. In the present review, we explore the therapeutic potential of garlic and its major constituents in PD, the molecular mechanisms responsible for its pharmaceutical activity, and the associated limitations that need to be overcome for its future potential use in clinical practice.

Garlic (Allium sativum L.) as an Ally in the Treatment of Inflammatory Bowel Diseases

For centuries, garlic (Allium sativum) has been used both as a traditional remedy for most health-related ailments and for culinary purposes. Current preclinical investigations have suggested that dietary garlic intake has beneficial health effects, such as antioxidant, anti-inflammatory, antitumor, antiobesity, antidiabetic, antiallergic, cardioprotective, and hepatoprotective effects. Its therapeutic potential is influenced by the methods of use, preparation, and extraction. Of particular importance is the Aged Garlic Extract (AGE). During the aging process, the odorous, sour, and irritating compounds in fresh raw garlic, such as allicin, are naturally converted into stable and safe compounds that have significantly greater therapeutic effects than fresh garlic. In AGE, S-allylcysteine (SAC) and S-allylmercaptocysteine (SAMC) are the major water-soluble organosulfurized compounds (OSCs). SAC has been extensively studied, demonstrating remarkable antioxidant, anti-inflammatory, and immunomodulatory capacities. Recently, AGE has been suggested as a promising candidate for the maintenance of immune system homeostasis through modulation of cytokine secretion, promotion of phagocytosis, and activation of macrophages. Since immune dysfunction plays an important role in the development and progress of various diseases, given the therapeutic effects of AGE, it can be thought of exploiting its immunoregulatory capacity to contribute to the treatment and prevention of chronic inflammatory bowel diseases (IBD).

S-allylcysteine potently protects against PhIP-induced DNA damage via Nrf2/AhR signaling pathway modulation in normal human colonic mucosal epithelial cells

SCOPE

This study aimed to investigate whether S-allylcysteine (SAC) exerts chemoprophylactic effects on foodborne carcinogenicity caused by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in normal human colonic mucosal epithelial cells.

METHODS AND RESULTS

Cellular thermal shift assays showed that SAC had an affinity for the Keap1 protein. Moreover, SAC may also dampen the binding of Keap1 and NF-E2-related factor 2 (Nrf2) by inhibiting p-p38 and increasing the phosphorylation of ERK1/2 and AKT, thereby inducing Nrf2/HO-1 signaling and upregulating the ratio of GSH to GSH/GSSG, which inhibits PhIP-induced oxidative stress and DNA damage. In addition, SAC significantly downregulates the aryl hydrocarbon receptor signaling pathway, suggesting that SAC may potentially impede the metabolic transformation of carcinogens.

CONCLUSION

Collectively, these findings suggest that SAC protects against PhIP-induced reactive oxygen species production and DNA damage by modulating the Nrf2/AhR signaling pathway, which may have significant potential as a novel chemopreventive agent. This article is protected by copyright. All rights reserved.

Antioxidant Interactions between S-allyl-L-cysteine and Polyphenols Using Interaction Index and Isobolographic Analysis

This work aims to study the antioxidant interactions between S-allyl-L-cysteine (SAC) and six natural polyphenols (quercetin, caffeic acid, sinapic acid, catechin, ferulic acid, and 3,4-dihydroxybenzoic acid) through the measurement of free-radical-scavenging activity of 1,1-diphenyl- 2-picryl-hydrazyl (DPPH), the radical-cation-scavenging activity of 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and reducing power. Among the six natural polyphenols, caffeic acid showed the strongest synergistic effect with SAC according to DPPH and reducing power assays. Further investigations based on the results of interaction index and isobologram analysis showed that the antioxidant activity (DPPH, ABTS, and reducing power) of the combination of caffeic acid with SAC presented an increase with the raising of their individual concentrations in their mixture and along with a dose–response manner. The best synergistic effect between caffeic acid and SAC based on DPPH, ABTS, and reducing power assays were observed at the ratio of 1:20, 1:35, and 1:70, respectively. The excellent synergic antioxidant activity of the combination of caffeic acid with SAC in our study suggests SAC has a more broad and effective application prospects in food field.

Beneficial Effects of N-Acetyl-L-cysteine or Taurine Pre- or Post-treatments in the Heart, Spleen, Lung, and Testis of Hexavalent Chromium-Exposed Mice

Hexavalent chromium[Cr(VI)] compounds may induce toxic effects, possibly via reactive intermediates and radicals formed during Cr(VI) reduction. In this study, we probed the possible effects of N-acetyl-L-cysteine (NAC) and taurine pre- or post-treatments on Cr(VI)-induced changes in lipid peroxidation and nonprotein thiols (NPSH) in mice heart, lung, spleen, and testis tissues. The mice were randomly assigned to six groups, consisting of control, Cr(VI)-exposed (20 mg Cr/kg, intraperitoneal ,ip), NAC (200 mg/kg, ip) as pre-treatment and post-treatment, and taurine (1 g/kg, ip) pre-treatment and post-treatment groups. Lipid peroxidation and NPSH levels were determined and the results were compared with regard to tissue- and antioxidant-specific basis. Exposure to Cr(VI) significantly increased lipid peroxidation in all tissues as compared to the control (p < 0.05); and consistent with this data, NPSH levels were significantly decreased (p < 0.05). Notably, administration of NAC and taurine, either before or after Cr(VI) exposure, was able to ameliorate the lipid peroxidation (p < 0.05) in all tissues. In the case of NPSH content, while the decline could be alleviated by both NAC and taurine pre- and post-treatments in the spleen, diverging results were obtained in other tissues. The effects of Cr(VI) on the lung thiols were abolished by pre-treatment with NAC and taurine; however, post-treatments could not exert significant effect. While thiol depletion in the heart was totally replenished by NAC and taurine administrations, NAC pre-treatment was partially more effective than post-treatment. In contrast with lipid peroxidation data, NAC treatment could not provide a statistically significant beneficial effect on NPSH content of the testis, whereas the effect in this tissue by taurine was profound. Thus, these data highlight the importance of tissue-specific factors and the critical role of administration time. Overall, our data suggest that NAC and taurine may have potential in prevention of Cr(VI)-induced toxicity in the heart, lung, spleen, and testis tissues.

S-allyl-l-cysteine (SAC) protects hepatocytes from alcohol-induced apoptosis

Hepatocyte apoptosis is frequently observed in alcohol‐related liver disease (ARLD), which ranks among the 30 leading causes of death worldwide. In the current study, we explored the impact of S‐allyl‐l‐cysteine (SAC), an organosulfur component of garlic, on hepatocyte apoptosis induced by alcohol. Rat liver (BRL‐3A) cells were challenged by ethanol with or without SAC treatment. Cell death/viability, reactive oxygen species (ROS) generation, mitochondrial Cytochrome C release, and caspase 3 activity were then examined. We found that ethanol remarkably induced apoptosis of hepatocytes, while SAC treatment rescued ethanol‐induced hepatocyte injury, as demonstrated by cell counting kit‐8 (CCK8) assay, TUNEL assay, and annexin V/PI staining assay. Ethanol evoked ROS generation in BRL‐3A cells, and this was abated by SAC pretreatment, as indicated by 2′,7′‐dichlorofluorescin diacetate (DCFDA) staining assay. Moreover, ethanol suppressed cellular anti‐apoptotic protein B‐cell lymphoma‐2 (Bcl‐2) expression, increased pro‐apoptotic protein Bcl‐2‐associated X protein (Bax) expression, induced mitochondrial Cytochrome C release, and activated the caspase 3‐dependent apoptosis pathway in BRL‐3A cells. SAC was sufficient to abolish all these changes induced by ethanol, thereby revealing the molecular mechanisms underlying its protective effects. In conclusion, SAC protects hepatocytes from ethanol‐induced apoptosis and may be suitable for use as a novel anti‐apoptotic agent for treating ARLD.

Structure-function relationships of hydroxyl radical scavenging and chromium-VI reducing cysteine-tripeptides derived from rye secalin

The aim of the study was to determine the activity of four rye peptides and molecular descriptors responsible for the detected biological function. The activity was determined using hydroxyl radical scavenging and chromium-VI (Cr(VI) reducing assays while the density functional theory (DFT) was used for molecular descriptors (i.e. structure-activity relationships). It was found that at pH 7.4, peptide CQV had the highest Cr(VI) reducing activity (76%) followed by QCA (30.8%) while other peptides had less than 25% reduction. All tested peptides were less active at pH 3.0 and this was due to poor spatial proximity of thiol and amine on the glutamine side chain. In the hydroxyl radical scavenging assay, CQV had the highest activity with 28.9 ± 1.3% inhibition of the formation of HO radicals compared to 19.0-13.6% for other peptides. Cysteine at the N-terminal was important for both the reduction of chromium (pH 7.4) and the HO activity because S-H bond energies at that position were lower based on DFT calculations.

Aged garlic extract and S-allylcysteine prevent apoptotic cell death in a chemical hypoxia model

Background

Aged garlic extract (AGE) and its main constituent S-allylcysteine (SAC) are natural antioxidants with protective effects against cerebral ischemia or cancer, events that involve hypoxia stress. Cobalt chloride (CoCl₂) has been used to mimic hypoxic conditions through the stabilization of the α subunit of hypoxia inducible factor (HIF-1α) and up-regulation of HIF-1α-dependent genes as well as activation of hypoxic conditions such as reactive oxygen species (ROS) generation, loss of mitochondrial membrane potential and apoptosis. The present study was designed to assess the effect of AGE and SAC on the CoCl₂-chemical hypoxia model in PC12 cells.

Results

We found that CoCl₂ induced the stabilization of HIF-1α and its nuclear localization. CoCl₂ produced ROS and apoptotic cell death that depended on hypoxia extent. The treatment with AGE and SAC decreased ROS and protected against CoCl₂-induced apoptotic cell death which depended on the CoCl₂ concentration and incubation time. SAC or AGE decreased the number of cells in the early and late stages of apoptosis. Interestingly, this protective effect was associated with attenuation in HIF-1α stabilization, activity not previously reported for AGE and SAC.

Conclusions

Obtained results show that AGE and SAC decreased apoptotic CoCl₂-induced cell death. This protection occurs by affecting the activity of HIF-1α and supports the use of these natural compounds as a therapeutic alternative for hypoxic conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s40659-016-0067-6) contains supplementary material, which is available to authorized users.

Kinetics and Mechanism of Oxidation of d-Penicillamine in Acidified Bromate and Aqueous Bromine

The oxidation of the biologically active compound d-penicillamine (Depen) by acidic bromate has been studied. The stoichiometry of the reaction is strictly 1 : 1, in which Depen is oxidized only as far as the sulfonic acid with no cleavage of the C–S bond to yield sulfate. Electrospray ionization spectroscopy shows that Depen is oxidized through addition of oxygen atoms on the sulfur centre to successively yield sulfenic and sulfinic acids before the product sulfonic acid. In conditions of excess Depen over the oxidant, sulfenic acid was not observed. Instead, nearly quantitative formation of the dimer was obtained. The dimer, which is the d-penicillamine disulfide species, was formed from a reaction of the putative highly electrophilic sulfenic acid with unreacted Depen in a condensation-type reaction and not through a radical-mediated pathway. Further oxidation of the dimer is slow because it is the most stable intermediate in the oxidation of Depen. In excess oxidant conditions, negligible dimer formation is observed. The reaction of bromine with Depen gives a stoichiometry of 3 : 1 with the same sulfonic acid product. This reaction is so fast that it is essentially diffusion controlled. Our stopped-flow instrument could not capture the oxidation by the first 2 moles of bromine, only the section of the reaction in which the sulfinic acid is oxidized to sulfonic acid.

Met inactivation by S-allylcysteine suppresses the migration and invasion of nasopharyngeal cancer cells induced by hepatocyte growth factor

Purpose

Past studies have reported that S-allylcysteine (SAC) inhibits the migration and invasion of cancer cells through the restoration of E-cadherin, the reduction of matrix metalloproteinase (MMP) and Slug protein expression, and inhibition of the production of reactive oxygen species (ROS). Furthermore, evidence is emerging that shows that ROS induced by radiation could increase Met activation. Following on these reports of SAC and Met, we investigated whether SAC could suppress Met activation.

Materials and Methods

Wound healing, invasion, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium (MTT), soft agar colony forming, western blotting, and gelatin zymography assays were performed in the human nasopharyngeal cancer cell lines HNE1 and HONE1 treated with SAC (0, 10, 20, or 40 mM) and hepatocyte growth factor (HGF).

Results

This study showed that SAC could suppress the migration and invasion of HNE1 and HONE1 cell lines by inhibiting p-Met. An increase of migration and invasion induced by HGF and its decrease in a dose dependent manner by SAC in wound healing and invasion assays was observed. The reduction of p-Met by SAC was positively correlated with p-focal adhesion kinase (p-FAK) and p-extracellular related kinase (p-ERK in both cell lines). SAC reduced Slug, MMP2, and MMP9 involved in migration and invasion with the inhibition of Met-FAK signaling.

Conclusion

These results suggest that SAC inhibited not only Met activation but also the downstream FAK, Slug, and MMP expression. Finally, SAC may be a potent anticancer compound for nasopharyngeal cancer treated with radiotherapy.

Hypoglycemic, antihyperglycemic, and antioxidant effects of the edible plant Anoda cristata

ETHNOPHARMACOLOGICAL RELEVANCE

Some studies refer that the entire plant of Anoda cristata is consumed as food and medicine; in particular for treating diabetes, inflammation, fever, cough, and wounds. The aim of this study was to establish the preclinical efficacy of Anoda cristata as hypoglycemic and/or antihyperglycemic agent using well-known animal models.

MATERIALS AND METHODS

The acute toxicity was analyzed by the Lorke method. Acute hypoglycemic as well as oral glucose and sucrose tolerance tests were used to determine the hypoglycemic and antihyperglycemic action of Anoda cristata. Several preparations of the plant, including a mucilage (M), an aqueous (T-AE), a free mucilage aqueous (FM-AE), and an organic (OE) extracts, were tested in healthy and NA-STZ-hyperglycemic mice. Glibenclamide (15mg/kg), acarbose (5mg/kg ) and metformin (200mg/kg) were used as positive controls. The major compounds acacetin (1) and diosmetin (2), isolated from an infusion of the plant applying chromatographic methods, were evaluated as hypoglycemic agents using the same assays. The FM-AE was tested also in rats with metabolic syndrome induced by a high-fructose fed. Finally some assays were performed to determine the antioxidant capacity of the FM-AE in vitro.

RESULTS

The results demonstrated that the extracts and compounds from Anoda cristata were effective for reducing blood glucose levels in healthy and NA-STZ-hyperglycemic mice when compared with vehicle groups (p<0.05). The FM-AE exerted also positive effect over different biochemical parameters altered in rats with metabolic syndrome induced by a fructose diet. FM-AE has also antioxidant action effectively trapping ONOO(-) and ROO(•) radicals. The major flavonoids isolated from the plant, namely acacetin (1) and diosmetin (2), caused significant hypoglycemic effect and possessed antioxidant activity.

CONCLUSION

Anoda cristata is effective to diminish glucose levels in vivo and to ameliorate different disorders related with the metabolic syndrome in rats. According to the results, the efficacy of Anoda cristata preparations could be due to the presence of active principles with different mode of actions at the molecular level, including α-glycosidases inhibitors, insulin secretagogues, glucose entrapment and radical trapping agents.

Chemical and biochemical mechanisms underlying the cardioprotective roles of dietary organopolysulfides

Foods that are rich in organosulfides are highly regarded for their broad range of functions in disease prevention and health promotion since ancient time yet modern scientific study, particularly clinical studies could not agree with traditional wisdom. One of the complexities is due to the labile nature of organosulfides, which are often transformed to different structures depending on the processing conditions. The recent evidence on polysulfides as H₂S donors may open up a new avenue for establishing structure and health promotion activity relationship. To put this development into perspective, we carried out a review on the recent progress on the chemistry and biochemistry of organopolysulfides with emphasis on their cardioprotective property. First, we briefly surveyed the foods that are rich in polysulfides and their structural diversity. This is followed by in-depth discussion on the chemical transformations of polysulfides under various processing conditions. We further reviewed the potential action mechanisms of polysulfides in cardioprotection through: (a) hydrogen sulfide releasing activity; (b) radical scavenging activity; and (c) activity in enzyme inhibition and intervention of gene regulation pathways. Based on the literature trend, we can conclude that the emerging concept of organopolysulfides as naturally occurring H₂S donors is intriguing and warrants further research to establish the structure and activity relationship of the organopolysulfides as H₂S donors.

Computational evidence to design an appropriate candidate for the treatment of Alzheimer's disease through replacement of the heptamethylene linker of bis(7)tacrine with S-allylcysteine

Due to the multiple pathogens of Alzheimer's disease, multitarget-directed ligand (MTDL) design has been highly regarded in recent years.

Garlic-derived compound S-allylmercaptocysteine inhibits cell growth and induces apoptosis via the JNK and p38 pathways in human colorectal carcinoma cells

S-allylmercaptocysteine (SAMC) is an active compound that is derived from garlic and has been demonstrated to possess antitumor properties in vitro. The present study aimed to investigate the effect of SAMC and determine the underlying mechanism of this effect on human colorectal carcinoma cells. The SW620 cells were cultured with various concentrations of SAMC and cell viability was detected using an MTT assay. Analysis of apoptosis was performed using terminal deoxynucleotidyl-transferase-mediated deoxyuridine triphosphate nick end labeling. The c-Jun N-terminal kinase (JNK) and p38 mitogen activated protein kinase (p38) signaling pathways were investigated by polymerase chain reaction. SAMC was observed to reduce cell viability in a dose- and time-dependent manner, partially through the induction of apoptosis in human colorectal carcinoma cells. At the molecular level, SAMC induces apoptosis through JNK and p38 signaling pathways, increasing tumor protein p53 (p53) and Bax activation in the SW620 cells. The most effective concentration of SAMC for the induction of SW620 cell apoptosis was found to be 400 μM, which was confirmed through cell viability assays and apoptosis analysis. The current study indicated that SAMC inhibits cell proliferation and induces apoptosis of SW620 cells via the JNK and p38 pathways. The results from the current study demonstrated that SAMC must be further investigated as a novel preventive or therapeutic agent for the treatment of colorectal carcinoma, and potentially for use in other tumor types.

Anticonvulsant and antioxidant effects of Tilia americana var. mexicana and flavonoids constituents in the pentylenetetrazole-induced seizures

Tilia genus is commonly used around the world for its central nervous system properties; it is prepared as tea and used as tranquilizing, anticonvulsant, and analgesic. In this study, anticonvulsant activity of the Tilia americana var. mexicana inflorescences and leaves was investigated by evaluating organic and aqueous extracts (100, 300, and 600 mg/kg, i.p.) and some flavonoids in the pentylenetetrazole-induced seizures in mice. Moreover, antioxidant effect of these extracts and flavonoids was examined in an in vitro study by using spectrophotometric technique. Significant activity was observed in the methanol extract from inflorescences. An HPLC analysis of the methanol extract from inflorescences and leaves of Tilia allowed demonstrating the respective presence of some partial responsible flavonoid constituents: quercetin (20.09 ± 1.20 μg/mg and 3.39 ± 0.10 μg/mg), rutin (3.52 ± 0.21 μg/mg and 8.94 ± 0.45 μg/mg), and isoquercitrin (1.74 ± 0.01 μg/mg and 1.24 ± 0.13 μg/mg). In addition, significant but different antioxidant properties were obtained among the flavonoids and the extracts investigated. Our results provide evidence of the anticonvulsant activity of Tilia reinforcing its utility for central nervous system diseases whose mechanism of action might involve partial antioxidant effects due to the presence of flavonoids.

The protective role of antioxidants in the defence against ROS/RNS-mediated environmental pollution

Overproduction of reactive oxygen and nitrogen species can result from exposure to environmental pollutants, such as ionising and nonionising radiation, ultraviolet radiation, elevated concentrations of ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, asbestos, particulate matter, pesticides, dioxins and furans, polycyclic aromatic hydrocarbons, and many other compounds present in the environment. It appears that increased oxidative/nitrosative stress is often neglected mechanism by which environmental pollutants affect human health. Oxidation of and oxidative damage to cellular components and biomolecules have been suggested to be involved in the aetiology of several chronic diseases, including cancer, cardiovascular disease, cataracts, age-related macular degeneration, and aging. Several studies have demonstrated that the human body can alleviate oxidative stress using exogenous antioxidants. However, not all dietary antioxidant supplements display protective effects, for example, β-carotene for lung cancer prevention in smokers or tocopherols for photooxidative stress. In this review, we explore the increases in oxidative stress caused by exposure to environmental pollutants and the protective effects of antioxidants.

3,4-Dihydroxy-5-nitrobenzaldehyde (DHNB) is a potent inhibitor of xanthine oxidase: a potential therapeutic agent for treatment of hyperuricemia and gout

Hyperuricemia, excess of uric acid in the blood, is a clinical problem that causes gout and is also considered a risk factor for cardiovascular disease. The enzyme xanthine oxidase (XO) produces uric acid during the purine metabolism; therefore, discovering novel XO inhibitors is an important strategy to develop an effective therapy for hyperuricemia and gout. We found that 3,4-dihydroxy-5-nitrobenzaldehyde (DHNB), a derivative of the natural substance protocatechuic aldehyde, potently inhibited XO activity with an IC₅₀ value of 3 μM. DHNB inhibited XO activity in a time-dependent manner, which was similar to that of allopurinol, a clinical XO inhibitory drug. DHNB displayed potent mixed-type inhibition of the activity of XO, and showed an additive effect with allopurinol at the low concentration. Structure-activity relationship studies of DHNB indicated that the aldehyde moiety, the catechol moiety, and nitration at C-5 were required for XO inhibition. DHNB interacted with the molybdenum center of XO and was slowly converted to its carboxylic acid at a rate of 10⁻¹⁰ mol/L/s. In addition, DHNB directly scavenged free radical DPPH and ROS, including ONOO⁻ and HOCl. DHNB effectively reduced serum uric acid levels in allantoxanamide-induced hyperuricemic mice. Furthermore, mice orally given a large dose (500 mg/kg) of DHNB did not show any side effects, while 42% of allopurinol (500 mg/kg)-treated mice died and their offspring lost their fur. Thus, DHNB could be an outstanding candidate for a novel XO inhibitory drug that has potent activity and low toxicity, as well as antioxidant activity and a distinct chemical structure from allopurinol.

The antioxidant mechanisms underlying the aged garlic extract- and S-allylcysteine-induced protection

Aged garlic extract (AGE) is an odorless garlic preparation containing S-allylcysteine (SAC) as its most abundant compound. A large number of studies have demonstrated the antioxidant activity of AGE and SAC in both in vivo--in diverse experimental animal models associated to oxidative stress--and in vitro conditions--using several methods to scavenge reactive oxygen species or to induce oxidative damage. Derived from these experiments, the protective effects of AGE and SAC have been associated with the prevention or amelioration of oxidative stress. In this work, we reviewed different antioxidant mechanisms (scavenging of free radicals and prooxidant species, induction of antioxidant enzymes, activation of Nrf2 factor, inhibition of prooxidant enzymes, and chelating effects) involved in the protective actions of AGE and SAC, thereby emphasizing their potential use as therapeutic agents. In addition, we highlight the ability of SAC to activate Nrf2 factor--a master regulator of the cellular redox state. Here, we include original data showing the ability of SAC to activate Nrf2 factor in cerebral cortex. Therefore, we conclude that the therapeutic properties of these molecules comprise cellular and molecular mechanisms at different levels.

Natural antioxidant dihydroxybenzyl alcohol blocks ritonavir-induced endothelial dysfunction in porcine pulmonary arteries and human endothelial cells

Background

Patients with HIV have an increased incidence of pulmonary artery hypertension. This study was designed to determine if the naturally occurring antioxidant dihydroxybenzyl alcohol (DHBA) could counteract the deleterious effects of ritonavir (RTV), an HIV-protease inhibitor known to impair endothelial function and increase oxidative stress.

Material/Methods

Antioxidant assays were performed on DHBA in a cell free system. Glutathione (GSH) levels were measured in human pulmonary artery endothelial cells (HPAEC) to determine the effect of DHBA on the level of oxidative stress in cells treated with RTV. Myograph analysis was performed on porcine pulmonary artery (PA) rings after treatment with RTV and/or DHBA. Likewise, reactive oxygen species (ROS) production was assessed in porcine PA rings after RTV +/− DHBA using a lucigenin reaction. Immunohistochemical staining for endothelial nitric oxide synthase (eNOS) was also performed in porcine PAs treated as above.

Results

DHBA demonstrated significant antioxidant activity in a cell free system that surpassed that of vitamin C. Also, treatment with DHBA reduced RTV-induced reduction in endothelium-dependent vasorelaxation and eNOS staining and increased superoxide anion levels. Meanwhile, there was a reversal in RTV-induced oxidative stress leading to reduced GSH levels in HPAECs after treatment with DHBA.

Conclusions

These findings suggest that the naturally occurring antioxidant DHBA reduces the impairment of vasomotor functions caused by RTV in porcine PAs and reduces oxidative stress caused by RTV in HPAEC and porcine PA rings. This study indicates that DHBA may have clinical applications in the prevention or treatment of antiretroviral drugs-associated vascular complications in patients with HIV.

Role of allyl group in the hydroxyl and peroxyl radical scavenging activity of S-allylcysteine

S-Allylcysteine (SAC) is the most abundant compound in aged garlic extracts, and its antioxidant properties have been demonstrated. It is known that SAC is able to scavenge different reactive species including hydroxyl radical (•OH), although its potential ability to scavenge peroxyl radical (ROO•) has not been explored. In this work the ability of SAC to scavenge ROO• was evaluated, as well as the role of the allyl group (-S-CH(2)-CH═CH(2)) in its free radical scavenging activity. Two derived compounds of SAC were prepared: S-benzylcysteine (SBC) and S-propylcysteine (SPC). Their abilities to scavenge •OH and ROO• were measured. A computational analysis was performed to elucidate the mechanism by which these compounds scavenge •OH and ROO•. SAC was able to scavenge •OH and ROO•, in a concentration-dependent way. Such activity was significantly ameliorated when the allyl group was replaced by benzyl or propyl groups. It was shown for the first time that SAC is able to scavenge ROO•.

Protective effect of sulforaphane pretreatment against cisplatin-induced liver and mitochondrial oxidant damage in rats

In the present work was analyzed whether sulforaphane (SFN) may protect against cisplatin (CIS)-induced hepatic damage, oxidant stress and mitochondrial dysfunction. Four groups of male Wistar rats were studied: control, CIS, CIS+SFN and SFN. SFN was given i.p. (500 μg/kg/d × 3 days) before CIS administration (single i.p. injection, 10mg/kg). Rats were sacrificed 3 days after CIS injection to evaluate hepatic damage (histological analysis, liver/body weight ratio and serum activity of aspartate aminotransferase and alanine aminotransferase), oxidant stress (lipid peroxidation and protein carbonyl and glutathione content), antioxidant enzymes (catalase, glutathione reductase, glutathione peroxidase, glutathione-S-transferase and superoxide dismutase) in liver homogenates and isolated mitochondria and mitochondrial function (oxygen consumption using either malate/glutamate or succinate as substrates and the activity of mitochondrial complex I, II, II-III, IV and V). Furthermore it was evaluated if SFN is able to scavenge some reactive oxygen species in vitro. It was found that SFN prevents CIS-induced (a) hepatic damage, (b) oxidant stress and decreased activity of antioxidant enzymes in liver and mitochondria and (c) mitochondrial alterations in oxygen consumption and decreased activity of mitochondrial complex I. It was also found that the scavenging ability of SFN for peroxynitrite anion, superoxide anion, singlet oxygen, peroxyl radicals, hydrogen peroxide and hydroxyl radicals was very low or negligible. The hepatoprotective effect of SFN was associated to the preservation of mitochondrial function, antioxidant enzymes and prevention of liver and mitochondrial oxidant stress.

S-Allylcysteine, a garlic compound, protects against oxidative stress in 1-methyl-4-phenylpyridinium-induced parkinsonism in mice

S-Allylcysteine (SAC), the most abundant organosulfur compound in aged garlic extract, has multifunctional activity via different mechanisms and neuroprotective effects that are exerted probably via its antioxidant or free radical scavenger action. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mouse has been the most widely used model for assessing neuroprotective agents for Parkinson's disease. 1-Methyl-4-phenylpyridinium (MPP(+)) is the stable metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and it causes nigrostriatal dopaminergic neurotoxicity. Previous studies suggest that oxidative stress, via free radical production, is involved in MPP(+)-induced neurotoxicity. Here, we report on the neuroprotective effect of SAC against oxidative stress induced by MPP(+) in the striatum of C57BL/6J mice. Mice were pretreated with SAC (125 mg/kg ip) daily for 17 days, followed by administration of MPP(+) (0.72 mg/kg icv), and were sacrificed 24 h later to evaluate lipid peroxidation, different antioxidant enzyme activities, spontaneous locomotor activity and dopamine (DA) content. MPP(+) administration resulted in a significant decrease in DA levels in the striatum. Mice receiving SAC (125 mg/kg ip) had significantly attenuated MPP(+)-induced loss of striatal DA levels (32%). The neuroprotective effect of SAC against MPP(+) neurotoxicity was associated with blocked (100% of protection) of lipid peroxidation and reduction of superoxide radical production - indicated by an up-regulation of Cu-Zn-superoxide dismutase activity - both of which are indices of oxidative stress. Behavioral analyses showed that SAC improved MPP(+)-induced impairment of locomotion (35%). These findings suggest that in mice, SAC attenuates MPP(+)-induced neurotoxicity in the striatum and that an antioxidant effect against oxidative stress may be partly responsible for its observed neuroprotective effects.

S-allylcysteine reduces the MPTP-induced striatal cell damage via inhibition of pro-inflammatory cytokine tumor necrosis factor-α and inducible nitric oxide synthase expressions in mice

We have recently demonstrated that S-allylcysteine (SAC) induces protection on neurochemical, biochemical and behavioral markers of striatal damage in different neurotoxic animal models - including a murine model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridinium (MPTP) injection to mice - indicating that pro-oxidant reactions underlie neurotoxicity in these models (García et al. 2008). In this work we investigated whether SAC can protect the striatum of mice from the morphological alterations in the MPTP toxic model, and if this response is correlated with a reduction in pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) expressions, and further reduction in astrocyte activation (glial fibrillary acidic protein (GFAP) expression). The striatal tissue from MPTP injected animals (30 mg/kg, i.p., ×5 days) showed a significant degree of cell damage and enhanced immunoreactivities to GFAP, TNF-α and iNOS, as well as an enhanced number of apoptotic nuclei. Treatment of mice with SAC (120 mg/kg, i.p., ×5 days) in parallel to MPTP significantly reduced or prevented all these markers. Our results suggest that MPTP-induced morphological alterations recruit a pro-inflammatory component triggered by cytokine TNF-α release and nitric oxide formation, which is sensitive to the antioxidant properties of SAC. This antioxidant is an effective experimental tool to reduce the brain lesions associated with oxidative damage and inflammatory responses.

Hypochlorous acid scavenging activities of thioallyl compounds from garlic

The hypochlorous acid (HOCl) scavenging capacities of 10 garlic compounds containing modifications in the thioallyl group (-S-CH2CH ═ CH2) were determined by a catalase protection assay, and the corresponding structure-activity relationships using molecular descriptors were calculated. This scavenging activity was enhanced by increasing the number of S atoms or by the alanyl group (-CH2CH-NH2-COOH) and decreased in the absence of the C ═ C bond or in the presence of a sulfoxide group in the thioallyl group. Interestingly, S-allylcysteine and its corresponding sulfoxide (alliin) showed the highest and lowest HOCl-scavenging capacities, respectively. Quantitative modeling by multiple regression analysis and partial least-squares projections showed that the topological descriptor polar surface area and two electronic properties, namely, highest occupied molecular orbital and total energy, contributed mainly to variations in the HOCl scavenging activity of thioallyl compounds. These observations provide new insights on the antioxidant mechanism of garlic derivatives in processes involving HOCl production.

Aged garlic extract delays the appearance of infarct area in a cerebral ischemia model, an effect likely conditioned by the cellular antioxidant systems

Experimental evidence has shown that some garlic-derived products have a protective effect against ischemic brain injury. The present study was designed to investigate the effect of aged garlic extract (AGE), establish the therapeutic window, and determine its protective mechanism in a cerebral ischemia model. Animals were subjected to middle cerebral artery occlusion (MCAO) for 2h and treated with 1.2ml/kg body wt.(i.p.) of AGE 30min before, at the beginning of (0R), or 1h after reperfusion. The 0R treatment significantly reduced the size of the infarct area after 2h of reperfusion. Repeated doses subsequent to the 0R treatment (at 1, 2, or 3h after reperfusion) had no effect on the temporal window of protection. The protective 0R treatment with AGE prevented the increase in nitrotyrosine and the decrease in total superoxide dismutase, glutathione peroxidase, and extracellular superoxide dismutase activities induced by MCAO. These data indicate that AGE delays the effects of ischemia/reperfusion-induced neuronal injury. However, this treatment itself was not associated with a noticeable improvement in the neurological outcome, or with an effect on the inflammatory response. We conclude that the neuroprotective effect of AGE in the 0R treatment might be associated with control of the free-radical burst induced by reperfusion, preservation of antioxidant enzyme activity, and the delay of other pathophysiological processes.

Antioxidant strategy to rescue synaptosomes from oxidative damage and energy failure in neurotoxic models in rats: protective role of S-allylcysteine

The functional preservation of nerve endings since the early stages of toxicity in a given damaging insult-either acute or chronic-by means of antioxidant and neuroprotective agents is a primary need to design therapeutic strategies for neurodegenerative disorders, with particular emphasis on those diseases with excitotoxic and depleted energy metabolism components. S-allylcysteine (SAC), a well-known antioxidant agent, was tested as a post-treatment in different in vitro and in vivo neurotoxic models. Quinolinic acid (QUIN) was used as a typical excitotoxic/pro-oxidant inducer, 3-nitropropionic acid (3-NP) was employed as a mitochondrial function inhibitor, and their combination (QUIN + 3-NP) was also evaluated in in vitro studies. For in vitro purposes, increasing concentrations of SAC (10-100 microM) were added to isolated brain synaptosomes at different times (1, 3 and 6 h) after the incubation with toxins (100 microM QUIN, 1 mM 3-NP or the combination of QUIN (21 microM) + 3-NP (166 microM). Thirty minutes later, lipid peroxidation (LP) and mitochondrial dysfunction (MD) were evaluated. For in vivo studies, SAC (100 mg/kg, i.p.) was given to QUIN- or 3-NP-striatally lesioned rats for 7 consecutive days (starting 120 min post-lesion). LP and MD were evaluated 7 days post-lesion in isolated striatal synaptosomes. Circling behavior was also assessed. Our results describe a differential pattern of protection achieved by SAC, mostly expressed in the 3-NP toxic model, in which nerve ending protection was found within the first hours (1 and 3) after the toxic insult started, supporting the concept that the ongoing oxidative damage and energy depletion can be treated during the first stages of neurotoxic events.

Chemical and molecular mechanisms of antioxidants: experimental approaches and model systems

Free radicals derived from oxygen, nitrogen and sulphur molecules in the biological system are highly active to react with other molecules due to their unpaired electrons. These radicals are important part of groups of molecules called reactive oxygen/nitrogen species (ROS/RNS), which are produced during cellular metabolism and functional activities and have important roles in cell signalling, apoptosis, gene expression and ion transportation. However, excessive ROS attack bases in nucleic acids, amino acid side chains in proteins and double bonds in unsaturated fatty acids, and cause oxidative stress, which can damage DNA, RNA, proteins and lipids resulting in an increased risk for cardiovascular disease, cancer, autism and other diseases. Intracellular antioxidant enzymes and intake of dietary antioxidants may help to maintain an adequate antioxidant status in the body. In the past decades, new molecular techniques, cell cultures and animal models have been established to study the effects and mechanisms of antioxidants on ROS. The chemical and molecular approaches have been used to study the mechanism and kinetics of antioxidants and to identify new potent antioxidants. Antioxidants can decrease the oxidative damage directly via reacting with free radicals or indirectly by inhibiting the activity or expression of free radical generating enzymes or enhancing the activity or expression of intracellular antioxidant enzymes. The new chemical and cell-free biological system has been applied in dissecting the molecular action of antioxidants. This review focuses on the research approaches that have been used to study oxidative stress and antioxidants in lipid peroxidation, DNA damage, protein modification as well as enzyme activity, with emphasis on the chemical and cell-free biological system.

A gas chromatography-mass spectrometry method for the quantitation of N-nitrosoproline and N-acetyl-S-allylcysteine in human urine: application to a study of the effects of garlic consumption on nitrosation

Biomarkers in urine can provide useful information about the bioactivation of chemical carcinogens and can be used to investigate the chemoprotective properties of dietary nutrients. N-Nitrosoproline (NPRO) excretion has been used as an index for endogenous nitrosation. In vitro and animal studies have reported that compounds in garlic may suppress nitrosation and inhibit carcinogenesis. We present a new method for extraction and sensitive detection of both NPRO and N-acetyl-S-allylcysteine from urine. The latter is a metabolite of S-allylcysteine, which is found in garlic. Urine was acidified and the organic acids were extracted by reversed-phase extraction (RP-SPE) and use of a polymeric weak anion exchange (WAX-SPE) resin. NPRO was quantified by isotope dilution gas chromatography-mass spectrometry (GC-MS) using [13C5]NPRO and N-nitrosopipecolinic acid (NPIC) as internal standards. This method was used to analyze urine samples from a study that was designed to test whether garlic supplementation inhibits NPRO synthesis. Using this method, 2.4 to 46.0 ng NPRO/ml urine was detected. The method is straightforward and reliable, and it can be performed with readily available GC-MS instruments. N-Acetyl-S-allylcysteine was quantified in the same fraction and detectable at levels of 4.1 to 176.4 ng/ml urine. The results suggest that 3 to 5 g of garlic supplements inhibited NPRO synthesis to an extent similar to a 0.5-g dose of ascorbic acid or a commercial supplement of aged garlic extract. Urinary NPRO concentration was inversely associated with the N-acetyl-S-allylcysteine concentration. It is possible that allyl sulfur compounds found in garlic may inhibit nitrosation in humans.

Garlic: nature's protection against physiological threats

Currently reliance on natural products is gaining popularity to combat various physiological threats including oxidative stress, cardiovascular complexities, cancer insurgence, and immune dysfunction. The use of traditional remedies may encounter more frequently due to an array of scientific evidence in their favor. Garlic (Allium sativum) holds a unique position in history and was recognized for its therapeutic potential. Recent advancements in the field of immunonutrition, physiology, and pharmacology further explored its importance as a functional food against various pathologies. Extensive research work has been carried out on the health promoting properties of garlic, often referred to its sulfur containing metabolites i.e. allicin and its derivatives. Garlic in its preparations are effective against health risks and even used as dietary supplements such as age garlic extract (AGE) and garlic oil etc. Its components/formulations can scavenge free radicals and protect membranes from damage and maintains cell integrity. It also provides cardiovascular protection mediated by lowering of cholesterol, blood pressure, anti-platelet activities, and thromboxane formation thus providing protection against atherosclerosis and associated disorders. Besides this, it possesses antimutagenic and antiproliferative properties that are interesting in chemopreventive interventions. Several mechanisms have been reviewed in this context like activation of detoxification phase-I and II enzymes, reactive oxygen species (ROS) generation, and reducing DNA damage etc. Garlic could be useful in preventing the suppression of immune response associated with increased risk of malignancy as it stimulates the proliferation of lymphocytes, macrophage phagocytosis, stimulates the release of interleukin-2, tumor necrosis factor-alpha and interferon-gamma, and enhances natural killer cells. In this paper much emphasis has been placed on garlic's ability to ameliorate oxidative stress, core role in cardiovascular cure, chemopreventive strategies, and indeed its prospective as immune booster.

Anti-hypertensive nutraceuticals and functional foods

Epidemiological studies have demonstrated that elevated blood pressure is one of the major risk factors for stroke and coronary heart disease (CHD). A close association between blood pressure and the incidence of cardiovascular diseases is well established if systolic/diastolic blood pressure is above 140/90 mmHg. In recent years, nutraceuticals and functional foods have attracted considerable interest as potential alternative therapies for treatment of hypertension, especially for prehypertensive patients, whose blood pressure is marginally or mildly high but not high enough to warrant the prescription of blood pressure-lowering medications. This review summarizes the findings of recent studies on the chemistry, production, application, efficacy, and mechanisms of popular blood pressure-lowering nutraceuticals and functional foods including the Dietary Approaches to Stop Hypertension (DASH) diet plan, L-arginine, chlorogenic acid, fermented milk, garlic, onion, tea, soybean, ginger, hawthorn, and fish oil.

Lipid peroxidation, mitochondrial dysfunction and neurochemical and behavioural deficits in different neurotoxic models: protective role of S-allylcysteine

Experimental evidence on the protective properties of S-allylcysteine (SAC) was collected from three models exerting striatal toxicity. In the first model, SAC (120 mg kg(-1)x5) prevented lipoperoxidation (LP) and mitochondrial dysfunction (MD) in synaptosomal fractions from 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridinium-treated mice (30 mg kg(-1)), but without complete restoration of dopamine levels. In the second model, SAC (300 mg kg(-1)x 3), prevented LP and MD in synaptosomes from rats infused with 6-hydroxydopamine (8 microg microl(-1)) into the substantia nigra pars compacta, but again, without total reversion of depleted dopamine levels. In the third model, SAC (100 mg kg(-1)x 1) prevented MD in synaptosomes from rats injected with 3-nitropropionic acid (10 mg kg(-1)), but in contrast to the other models, it failed to prevent LP. SAC also prevented the aberrant motor activity patterns evoked by the three toxins. Altogether, the results suggest that the antioxidant properties of SAC are responsible for partial or total preservation of neurochemical, biochemical and behavioural markers, indicating that pro-oxidant reactions underlie the neurotoxicity in these models.