Dose-dependent influence of commercial garlic (Allium sativum) on rats fed cholesterol-containing diet

Effect of garlic powder tablet on carotid intima-media thickness in patients with coronary artery disease: a preliminary randomized controlled trial

BACKGROUND/OBJECTIVES

This study was designed to investigate whether garlic powder tablets in adjunct to conventional medical treatment could have an effect on carotid intima-media thickness (CIMT) and plasma lipoproteins and lipids in patients with coronary artery disease (CAD).

SUBJECTS/METHODS

A randomized, placebo-controlled, clinical trial was conducted on 56 patients with CAD between the ages of 25 and 75 years. The patients were randomly divided into two groups: garlic group (n = 27), receiving garlic powder tablet (1200 µg allicin/tab) twice daily and the placebo group (n = 29), receiving placebo for 3 months. The rate of atherosclerosis progression was measured by B-mode ultrasonography as the increase in CIMT.

RESULTS

After 3 months of taking garlic tablets, CIMT values had minor variations (0.009 ± 0.007 mm reduction from baseline), while in the placebo group, an increase in CIMT values was observed (0.04 ± 0.01 mm increase from baseline). After 3 months of treatment, mean CIMT difference from baseline was significantly differ between the two groups (p < 0.001). Plasma lipids and lipoproteins (total cholesterol, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, Apolipoprotein A1 and Apolipoprotein B) did not differ between the two groups.

CONCLUSIONS

The results suggest that dry garlic powder tablet is superior to placebo in prevention of CIMT progression in patients with CAD and may be considered as an adjunct treatment for atherosclerosis.

Blueberry juice causes potent relaxation of rat aortic rings via the activation of potassium channels and the H₂S pathway

The objective of this study was to investigate the in vitro effects of blueberry juice on healthy rat aortic rings, and to explore the roles of potassium channels and of the hydrogen sulphide (H(2)S) pathway in mediating the effects of blueberry juice. Firstly, the antioxidant capacity of blueberry juice was compared to other popular juice drinks using the Folin-Ciocalteu and the DPPH assays. Blueberry juice had significantly higher total polyphenol content than any of the other drinks studied (p < 0.01). The effect of blueberry juice on noradrenaline-contracted aortic rings was then observed, and the juice caused significant inhibition of noradrenaline-induced contractions (p < 0.01). Voltage-gated potassium channel (Kv) blockers 4-aminopyridine (1 mM) and 3,4-diaminopyridine (1 mM), as well as the cystathionine γ-lysase (CSE) inhibitor d,l-propargylglycine (2 mM) were then utilised to elucidate the role of Kv channels and the CSE/H(2)S pathway. Kv channel blocker 3,4-diaminopyridine caused significant blockade at 1/100 and 1/50 dilutions of juice (p < 0.01), whilst 4-aminopyridine caused significant blockade of the 1/100 dilution of blueberry juice (p < 0.05). In addition, d,l-propargylglycine potently inhibited the effect of 1/100 and 1/50 dilutions of blueberry juice (p < 0.01). This study indicates that blueberry juice has potent vasorelaxing properties, and thus may be a useful dietary agent for the prevention and treatment of hypertension. This study also provides strong evidence that Kv channels and the CSE/H(2)S pathway may be responsible, at least in part, for mediating the effects of blueberry juice.

Garlic extract reduces serum angiotensin converting enzyme (ACE) activity in nondiabetic and streptozotocin-diabetic rats

The rennin-angiotensin system (RAS) has been implicated in the development of diabetic vascular complications. Peptidyl-dipeptidase A (angiotensin converting enzyme, ACE) has a major role in this system. The aim of the present study was to clarify the effect of intraperitoneal administration of aqueous garlic extract (Allium sativum) on the serum ACE activity of streptozotocin (STZ)-diabetic and nondiabetic rats. Although garlic extract administration had no significant effect on serum glucose, it significantly strongly decreased the serum ACE activity. ACE activity was higher in diabetic than nondiabetic rats, but in diabetic animals treated with garlic extract, the elevation of ACE activity did not occur. These results suggest that garlic extract might have value as ACE inhibitor to prevent some vascular complications of diabetes mellitus.

The bioactivity of processed garlic (Allium sativum L.) as shown in vitro and in vivo studies on rats

Garlic (Allium sativum L.) is widely used as an obligatory part in many cooked dishes loosing during this process a certain part of its bioactivity. Antioxidant capacity measured by the ferric-reducing/antioxidant power (FRAP) method and by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical assay was the highest in raw and in a short time processed garlic samples by cooking. 70 Wistar rats were randomly divided into 10 diet groups, each of seven. They were named Control, NPG, PG1, PG2, PG3, Chol, Chol/NPG, Chol/PG1, Chol/PG2 and Chol/PG3. The rats of the Control group were fed basal diet (BD), which included wheat starch, casein, soybean oil, cellulose, mineral and vitamin mixtures. To the BD of the nine other groups were added 25mg of lyophilized non processed garlic equivalent of 500 mg non processed garlic/kg body weight (NPG), the same quantity of processed garlic for 20, 40 and 60 min for PG1, PG2 and PG3, respectively, 1% of cholesterol (Chol), 1% of cholesterol and 25mg/kg body weight of lyophilized non processed garlic (Chol/NPG), 1% of cholesterol and the same quantity of processed garlic for 20, 40 and 60 min for Chol/PG1, Chol/PG2 and Chol/PG3, respectively. The dose of 500 mg (25mg of lyophilized garlic/kg body weight) was chosen as the most effective (Banerjee, S.K., Maulik, M., Mancahanda, S.C., Dinda, A.K., Gupta, S.K., Maulik, S.K., 2002. Dose-dependent induction of endogenous antioxidants in rat heart by chronic administration of garlic. Life Sciences 70, pp. 1509-1518). Plasma lipid profile and the total antioxidant capacity in rats significantly differed in diet groups with addition of garlic samples cooked for a long time. In summary, garlic cooked for a short time preserves a high bioactivity of non processed garlic. The diet supplemented with these samples and cholesterol improved lipid indices, decreased fibrinogen and increased antioxidant activity in plasma of rats. Therefore, for preservation of garlic bioactivity optimal regime has to be used.