Neuroprotective Effects of Garlic A Review

Current studies and potential future research directions on biological effects and related mechanisms of allicin

Allicin, a thiosulfonate extract from freshly minced garlic, has been reported to have various biological effects on different organs and systems of animals and human. It can reduce oxidative stress, inhibit inflammatory response, resist pathogen infection and regulate intestinal flora. In addition, dozens of studies also demonstrated allicin could reduce blood glucose level, protect cardiovascular system and nervous system, and fight against cancers. Allicin was widely used in disease prevention and health care. However, more investigations on human cohort study are needed to verify the biological or clinical effects of allicin in the future. In this review, we summarized the biological effects of allicin from previous outstanding and valuable studies and provided useful information for future studies on the health effects of allicin.

The effect of garlic (Allium sativum) supplementation on the lipid parameters and blood pressure levels in women with polycystic ovary syndrome: A randomized controlled trial

Polycystic ovary syndrome (PCOS) is the most prevalent female endocrine-related disorder in reproductive ages. The aim of the study was to investigate the effect of garlic on the lipid parameters and blood pressure levels in women with PCOS. The present study was a randomized, double-blinded control trial, conducted on 80 PCOS patients. Participants were taught to intake either a total 800 mg/day garlic supplement or an identical placebo (starch) after lunch for 8 weeks. Physical activity, diet intake, anthropometric measures, and blood pressure were evaluated at baseline and end of the study. The blood sample was also taken to assess the change in outcomes of interest at the pre- and post-intervention. Garlic supplementation significantly reduced serum total cholesterol (change mean difference: -8.05, 95% CI: -15.47, -0.62) and LDL-C (change mean difference: -7.67, 95%CI: -14.64, -0.70) levels in comparison to the control group. In addition, a trend to a significant decrease was found in serum triglyceride levels and Systolic blood pressure; however, no significant difference was observed between two groups in HDL-C and diastolic blood pressure levels. The present study suggested that garlic supplementation might be effective on lipid markers improvement. Further studies are needed to confirm our findings.

Neuroprotective effects of garlic extract on dopaminergic neurons of substantia nigra in a rat model of Parkinson's disease: motor and non-motor outcomes

Parkinson's disease (PD) is a common and severe neurodegenerative disorder associated with a selective loss of dopaminergic neurons in substantia nigra pars compacta. The crucial role of oxidative stress and inflammation in PD onset and progression is evident. It has been proven that garlic extract (GE) protects the cells from oxidative stress, inflammation, mitochondrial dysfunction and apoptosis. That is, we aimed to investigate if GE reveals protective features on the preclinical model of PD. The study has been designed to evaluate both preventive (GE administered before 6-OHDA injection) and therapeutic (GE administered after 6-OHDA injection) effects of GE on the animal model. Forty male Wistar rats were divided into 4 groups including control, lesion, treatment I (received GE before 6-OHDA injection) and treatment II (received GE both before and after 6-OHDA injection). At the end of treatment, hanging, rotarod, open field and passive avoidance tests as well as immunohistochemistry were performed to evaluate the neuroprotective effects of garlic against PD. Our immunohistochemistry analysis revealed that the tyrosine hydroxylase positive cells (TH+) in GE treated groups were significantly higher (p˂0.001) than the lesion group. The motor deficiency significantly improved in hanging, rotarod, open-field and apomorphine-induced rotational tests. We observed an attenuation in memory impairment induced by PD on GE treated group. Therefore, we found that GE protects dopaminergic neurons in 6-OHDA-induced neurotoxicity and ameliorates movement disorders and behavioral deficits.

Internalization of Garlic-Derived Nanovesicles on Liver Cells is Triggered by Interaction With CD98

The mechanism of how plant-derived nanovesicles are uptaken by cells remains unknown. In this study, the garlic-derived nanovesicles (GDVs) were isolated and digested with trypsin to remove all surface proteins. Digested GDVs showed less uptake compared to undigested GDVs, confirming that the surface proteins played a role in the endocytosis. On the cell side (HepG2), interestingly, blocking the CD98 receptors significantly reduced the uptake of GDVs. During the cellular internalization of GDVs, we observed that some surface proteins of GDVs were co-localized with CD98. A total lysate of the GDV surface showed a high presence of a mannose-specific binding protein, II lectin. Blocking GDV II lectin (using mannose preincubation) highly reduced the GDV internalization, which supports that direct interaction between II lectin and CD98 plays an important role in internalization. The GDVs also exhibited in vitro anti-inflammatory effect by downregulating proinflammatory factors on the HepG2 cells. This work contributes to understanding a part of the GDV internalization process and the cellular anti-inflammatory effects of garlic.