Garlic in Clinical Practice: An Evidence-Based Overview

The role of sulfur compounds in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease that brings about great social and economic burden, with oxidative stress and inflammation affecting the whole disease progress. Sulfur compounds such as hydrogen sulfide (H₂S), thiols, and persulfides/polysulfides have intrinsic antioxidant and anti-inflammatory ability, which is engaged in the pathophysiological process of COPD. Hydrogen sulfide mainly exhibits its function by S-sulfidation of the cysteine residue of the targeted proteins. It also interacts with nitric oxide and acts as a potential biomarker for the COPD phenotype. Thiols’ redox buffer such as the glutathione redox couple is a major non-enzymatic redox buffer reflecting the oxidative stress in the organism. The disturbance of redox buffers was often detected in patients with COPD, and redressing the balance could delay COPD exacerbation. Sulfane sulfur refers to a divalent sulfur atom bonded with another sulfur atom. Among them, persulfides and polysulfides have an evolutionarily conserved modification with antiaging effects. Sulfur compounds and their relative signaling pathways are also associated with the development of comorbidities in COPD. Synthetic compounds which can release H₂S and persulfides in the organism have gradually been developed. Naturally extracted sulfur compounds with pharmacological effects also aroused great interest. This study discussed the biological functions and mechanisms of sulfur compounds in regulating COPD and its comorbidities.

The association of garlic intake and cardiovascular risk factors: A systematic review and meta-analysis

Garlic is a common cooking ingredient and used in traditional medicine in Asian countries. There is a growing attention on garlic due to its preventive characteristics in cardiovascular diseases (CVDs). Many studies have reviewed the association between garlic intake and CVDs; however, no consistent conclusions have been drawn. New clinical trials have also been conducted and could contribute to more solid statements. In order to systematically review the reliability of previous studies regarding the implication of garlic in the management of CVDs, we performed in-depth meta-analysis using the most up-to-date randomized clinical trials (RCTs) data with more systematic controls. According to the 22 studies included, the effects of garlic intake on lowering total cholesterol (TC) and low-density lipoprotein (LDL) are more noticeable with lower dosage and longer duration, especially in patients with CVDs. In addition, subgroup analysis indicated that appropriate diet intervention could be an important control factor that should be taken into consideration in any future study designs.

An Evaluation of Traditional Persian Medicine for the Management of SARS-CoV-2

A new coronavirus causing severe acute respiratory syndrome (SARS-CoV-2) has emerged and with it, a global investigation of new antiviral treatments and supportive care for organ failure due to this life-threatening viral infection. Traditional Persian Medicine (TPM) is one of the most ancient medical doctrines mostly known with the manuscripts of Avicenna and Rhazes. In this paper, we first introduce a series of medicinal plants that would potentially be beneficial in treating SARS-CoV-2 infection according to TPM textbooks. Then, we review medicinal plants based on the pharmacological studies obtained from electronic databases and discuss their mechanism of action in SARS-CoV-2 infection. There are several medicinal plants in TPM with cardiotonic, kidney tonic, and pulmonary tonic activities, protecting the lung, heart, and kidney, the three main vulnerable organs in SARS-CoV-2 infection. Some medicinal plants can prevent "humor infection", a situation described in TPM which has similar features to SARS-CoV-2 infection. Pharmacological evaluations are in line with the therapeutic activities of several plants mentioned in TPM, mostly through antiviral, cytoprotective, anti-inflammatory, antioxidant, and anti-apoptotic mechanisms. Amongst the primarily-introduced medicinal plants from TPM, rhubarb, licorice, garlic, saffron, galangal, and clove are the most studied plants and represent candidates for clinical studies. The antiviral compounds isolated from these plants provide novel molecular structures to design new semisynthetic antiviral agents. Future clinical studies in healthy volunteers as well as patients suffering from pulmonary infections are necessary to confirm the safety and efficacy of these plants as complementary and integrative interventions in SARS-CoV-2 infection.

Herbal supplements for health promotion and disease prevention

This three-part series is designed to provide clinicians with a working knowledge of using herbal supplements for health and disease states. Common herbal preparations used for health promotion or disease prevention will be featured in this part of the series.

Quantitative ethnomedicinal survey of medicinal plants given for cardiometabolic diseases by the non-institutionally trained siddha practitioners of Tiruvallur district, Tamil Nadu, India

ETHNOBOTANICAL RELEVANCE

The burden of cardiometabolic diseases such as dyslipidemia, hyperglycemia, hypertension, visceral obesity and atherosclerotic cardiovascular diseases and the use of traditional medicine for the management of such diseases are high in India; hence there is a need to document and analyze such therapies.

AIM OF THE STUDY

This study documented and analyzed the medicinal plants prescribed for cardiometabolic diseases by the non-institutionally trained siddha practitioners of Tiruvallur district of Tamil Nadu, India.

METHODOLOGY

The field survey was conducted between December 2014 to November 2015. Successive free listing assisted with field-walks was used to interview the informants. After assessing the sampling sufficiency using rarefaction curve analysis, indices such as Informant Consensus Factor (Fic) and Index of Agreement on Remedies (IAR) were calculated for the data. The indicators of informant's medicinal plant knowledge such as Shannon's index, equitability index, etc., were regressed with the demographic profile of the informants.

RESULTS

For this study 70 non-institutionally trained Siddha medical practitioners were approached; the data from 36 practitioners who were treating cardiometabolic diseases were documented. This study recorded the use of 188 species which were used to prepare 368 formulations to treat illnesses categorized under cardiometabolic diseases. In this, 53.04% claims were singletons. Regression analysis showed that single species dominance was reduced and the diversity of medicinal plants was increased with the increase in the age and experience. Increase in the years of formal education increased the equitability in the uses. The plants such as Nelumbo nucifera Gaertn. (cardiovascular diseases), Allium sativum L. (dyslipidemia), Cuminum cyminum L. (hypertension), Macrotyloma uniflorum Verdc. (obesity) and Azadirachta indica A. Juss. (type 2 diabetes) were the highly cited medicinal plants.

CONCLUSION

This survey has identified the plants most commonly used by Siddha practitioners of Tiruvallur district, Tamil Nadu, India for cardiometabolic diseases. The prevalence of chronic, non-communicable metabolic illnesses such as type 2 diabetes, hypertension and obesity are increasing worldwide due to the rapid changes in the lifestyle. These ailments require a life-long care and in such instances, people tend to use complementary therapies in most cases, alongside with conventional therapies. In view of the high use of traditional therapies for treating cardiometabolic illnesses, this study supports the need for more research to evaluate the potential benefits of the treatments and to identify any safety concern.

Influence of pH, concentration and light on stability of allicin in garlic (Allium sativum L.) aqueous extract as measured by UPLC

BACKGROUND

Garlic is one of the most important bulb vegetables and is mainly used as a spice or flavoring agent for foods. It is also cultivated for its medicinal properties, attributable to sulfur compounds, of which allicin is the most important. However, the stability of allicin in garlic extract is not well understood. In this study, using UPLC, the stability of allicin extracted in water from garlic was evaluated in phosphate buffer at different temperatures under light and dark conditions.

RESULTS

At room temperature, allicin in aqueous extract was most stable at pH 5-6 but degraded quickly at lower or higher pH. It began to degrade within 0.5 h and was not detectable after 2 h when the pH was higher than 11 or lower than 1.5. It degraded quickly when the temperature was higher than 40 °C and especially higher than 70 °C. At room temperature, allicin in water could be stored for 5 days without obvious degradation. Higher concentrations of allicin in solution were somewhat more stable than low concentrations.

CONCLUSION

Allicin extract was sensitive to pH and temperature of storage but not to light. Higher-concentration allicin solution was more stable.

Glutathione-garlic sulfur conjugates: slow hydrogen sulfide releasing agents for therapeutic applications

Natural organosulfur compounds (OSCs) from Allium sativum L. display antioxidant and chemo-sensitization properties, including the in vitro inhibition of tumor cell proliferation through the induction of apoptosis. Garlic water- and oil-soluble allyl sulfur compounds show distinct properties and the capability to inhibit the proliferation of tumor cells. In the present study, we optimized a new protocol for the extraction of water-soluble compounds from garlic at low temperatures and the production of glutathionyl-OSC conjugates during the extraction. Spontaneously, Cys/GSH-mixed-disulfide conjugates are produced by in vivo metabolism of OSCs and represent active molecules able to affect cellular metabolism. Water-soluble extracts, with (GSGaWS) or without (GaWS) glutathione conjugates, were here produced and tested for their ability to release hydrogen sulfide (H₂S), also in the presence of reductants and of thiosulfate:cyanide sulfurtransferase (TST) enzyme. Thus, the TST catalysis of the H₂S-release from garlic OSCs and their conjugates has been investigated by molecular in vitro experiments. The antiproliferative properties of these extracts on the human T-cell lymphoma cell line, HuT 78, were observed and related to histone hyperacetylation and downregulation of GAPDH expression. Altogether, the results presented here pave the way for the production of a GSGaWS as new, slowly-releasing hydrogen sulfide extract for potential therapeutic applications.

Allicin induces apoptosis of the MGC-803 human gastric carcinoma cell line through the p38 mitogen-activated protein kinase/caspase-3 signaling pathway

Gastric cancer is one of the most common forms of malignant tumor, and the development of anti‑gastric cancer drugs with minimal toxicity is of clinical importance. Allicin is extracted from Allium sativum (garlic). Recent research, including clinical experiments, has shown that garlic has anticancer and tumor suppressive effects. The present study aimed to investigate the effects of allicin on the MGC‑803 human gastric carcinoma cell line, and to further explore the possible mechanisms of its tumor suppressor effects. The effects of allicin on the MGC‑803 cells were initially examined using an 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide assay. Hoechst staining was also used, in order to demonstrate the impact of allicin on MGC‑803 cell apoptosis. In addition, western blot analysis was performed to determine the abnormal expression levels of apoptosis‑associated proteins, following the treatment of MGC‑803 cells with allicin. Western blotting was also used to investigate the specific mechanisms underlying allicin‑induced apoptosis of MGC‑803 cells. The rate of MGC‑803 apoptosis was significantly increased, when the concentration and treatment time of allicin were increased. Hoechst staining detected an enhanced rate of apoptosis, and enhanced expression levels of cleaved caspase 3 were determined by western blotting. Notably, the protein expression levels of p38 were increased when the MGC‑803 cells were treated with allicin. The results of the present study suggest that allicin may inhibit the proliferation and induce the apoptosis of MGC‑803 human gastric carcinoma cells, and this may partially be achieved through the enhanced expression of p38 and cleaved caspase 3.

Protective effects of garlic extract, PMK-S005, against nonsteroidal anti-inflammatory drugs-induced acute gastric damage in rats

BACKGROUND

PMK-S005 is synthetic s-allyl-L-cysteine (SAC), a sulfur-containing amino acid, which was initially isolated from garlic. The antioxidant and anti-inflammation activities of SAC have been demonstrated in diverse experimental animal models.

AIMS

The purpose of this study was to investigate the gastroprotective effects of PMK-S005 against NSAIDs-induced acute gastric damage in rats.

METHODS

Eight-week SD rats were pretreated with PMK-S005 (1, 5, or 10 mg/kg) or rebamipide (50 mg/kg) 1 h before administration of NSAIDs including aspirin (200 mg/kg), diclofenac (80 mg/kg), and indomethacin (40 mg/kg). After 4 h, the gross ulcer index, histological index, and gastric mucus level were determined. Myeloperoxidase (MPO), TNF-α, IL-1β, PGE2, and LTB4 levels were estimated in the gastric mucosal tissue by ELISA. Protein expressions of cPLA2, COX-1, and COX-2 were assessed by Western blot analysis.

RESULTS

Pretreatment with PMK-S005 significantly attenuated the NSAIDs-induced gastric damage and increased the gastric mucus level. In addition, PMK-S005 attenuated increases in MPO, TNF-α, and IL-1β production. The expressions of cPLA2 and COX-2 induced by NSAIDs were decreased by PMK-S005 pretreatment. PMK-S005 did not cause suppression of PGE2 synthesis induced by NSAIDs, but LTB4 production was significantly suppressed by PMK-S005. The effects of PMK-S005 were consistently maximized at a concentration of 5 mg/kg, which were frequently superior to those of rebamipide.

CONCLUSIONS

These results strongly suggest that PMK-S005 can be a useful gastroprotective agent against acute gastric mucosal damage by suppressing proinflammatory cytokines, down-regulating cPLA2, COX-2 and LTB4 expression, and increasing the synthesis of mucus.

Garlic extract attenuates brain mitochondrial dysfunction and cognitive deficit in obese-insulin resistant rats

Oxidative stress in the obese-insulin resistant condition has been shown to affect cognitive as well as brain mitochondrial functions. Garlic extract has exerted a potent antioxidant effect. However, the effects of garlic extract on the brain of obese-insulin resistant rats have never been investigated. We hypothesized that garlic extract improves cognitive function and brain mitochondrial function in obese-insulin resistant rats induced by long-term high-fat diet (HFD) consumption. Male Wistar rats were fed either normal diet or HFD for 16 weeks (n = 24/group). At week 12, rats in each dietary group received either vehicle or garlic extract (250 and 500 mg·kg(-1)·day(-1)) for 28 days. Learning and memory behaviors, metabolic parameters, and brain mitochondrial function were determined at the end of treatment. HFD led to increased body weight, visceral fat, plasma insulin, cholesterol, and malondialdehyde (MDA) levels, indicating the development of insulin resistance. Furthermore, HFD rats had cognitive deficit and brain mitochondrial dysfunction. HFD rats treated with both doses of garlic extract had decreased body weight, visceral fat, plasma cholesterol, and MDA levels. Garlic extract also improved cognitive function and brain mitochondrial function, which were impaired in obese-insulin resistant rats caused by HFD consumption.

Thiosulfoxide (sulfane) sulfur: new chemistry and new regulatory roles in biology

The understanding of sulfur bonding is undergoing change. Old theories on hypervalency of sulfur and the nature of the chalcogen-chalcogen bond are now questioned. At the same time, there is a rapidly expanding literature on the effects of sulfur in regulating biological systems. The two fields are inter-related because the new understanding of the thiosulfoxide bond helps to explain the newfound roles of sulfur in biology. This review examines the nature of thiosulfoxide (sulfane, S0) sulfur, the history of its regulatory role, its generation in biological systems, and its functions in cells. The functions include synthesis of cofactors (molybdenum cofactor, iron-sulfur clusters), sulfuration of tRNA, modulation of enzyme activities, and regulating the redox environment by several mechanisms (including the enhancement of the reductive capacity of glutathione). A brief review of the analogous form of selenium suggests that the toxicity of selenium may be due to over-reduction caused by the powerful reductive activity of glutathione perselenide.

The effect of nutritional supplements on serum high-density lipoprotein cholesterol and apolipoprotein A-I

One of the factors contributing to the increased risk of developing premature atherosclerosis is low plasma concentrations of high-density lipoprotein (HDL) cholesterol. Multiple potential mechanisms account for the cardioprotective effects of HDL and its main protein apolipoprotein A-I (apo A-I). Diet has an important role in modulating HDL cholesterol level. The widespread use of nutritional supplements may also alter the biology of HDL. In this review, we discuss the effect of select nutritional supplements on serum HDL cholesterol and apo A-I levels. Some nutritional supplements, such as phytosterols, soy proteins, and black seed extracts, may increase HDL cholesterol levels, while others such as cholic acid and high doses of commonly used antioxidant vitamins may downregulate HDL cholesterol levels and reduce its cardioprotection. Multiple mechanisms are involved in the regulation of HDL levels, so changes in production and clearance of HDL may have different clinical implications. The clinical relevance of the changes in HDL and apo A-I caused by nutrient supplementation needs to be tested in controlled clinical trials.