Introduction

Garlic (Allium sativum) is one of the most researched plants, with a long history of medicinal use¹. Many of its constituents contribute to its medicinal properties and potential to lower the risk of diseases². Various formulations of garlic exist, which include raw garlic homogenate³, garlic powder⁴, aged garlic extract², steam-distilled garlic⁵, etc. Aqueous extract of garlic is a form of raw garlic homogenate⁶. The important components, among others, include allicin (allyl 2-propenethiosulfinate or diallyl thiosulfinate) which is thought to be the chief bioactive compound present in aqueous garlic extract; allyl methyl thiosulfonate, 1-propenyl allyl thiosulfonate and γ-L-glutamyl-S-alkyl-L-cysteine⁶. Garlic preparations are known for their cardioprotective effects^7,8, ability to lower blood pressure⁹ in people with high blood pressure, lower lipid levels, reduce the risk of atherosclerosis⁶, increase blood levels of antioxidant enzymes, and also offer some benefits in conditions like diabetes mellitus and cancer¹⁰. Although many positive health effects have been attributed to the use of garlic, the effects tend to be undesirable on testicular functions, as many studies have observed some adverse effects on reproductive functions. Although the mechanisms of this action of garlic are not very clear, apoptosis has been suggested to be a likelihood¹¹. Allium sativum is an antioxidant and a detoxifying agent, which scavenges the reactive oxygen species (ROS), enhancing the ^{cellular antioxidant enzymes, (such as superoxide dismutase, catalase, glutathione peroxidase, etc) thereby protecting the cells against disease-causing oxidative damage2. Administration of garlic can alter the activities of endogenous antioxidants, depending on the dosage as well as the type of antioxidants12. Studies by Banerjee et al12 showed that use of garlic at low doses could significantly increase superoxide dismutase (SOD), whereas at higher doses, the activity of SOD is reduced. Garlic causes a dose-dependent increase in the percentage of empty seminiferous tubules, thereby altering spermatogenesis and reducing testosterone secretion13,11. Meanwhile, studies by Oi et al14 found an increased testicular testosterone with garlic supplementation. Also associated with garlic use is the inhibition of Leydig steroidogenic enzyme expression and Sertoli cell markers, which are capable of inducing apoptosis in testicular germ cells (spermatocytes and spermatids), characterised by increased levels of active Caspase 3 (CASP3)11.}

In the present study, the effect of orally administered aqueous extract of Allium sativum was studied on some semen parameters in wistar rats and its effect on erythrocyte superoxide dismutase (SOD).

Materials and Methods

Preparation of Garlic Aqueous Extract

Experimental Animals

Experimental Pharmacological Protocol

Animal Sacrifice and Sample Collection

Assay of Superoxide Dismutase (SOD) Activity

Epididymal Sperm Concentration

Sperm Motility

Sperm Morphology

Statistical analysis

Results

There were no statistically significant changes in the body weight difference of the experimental animals in all the groups, and the ratio of the testis weight to that of the body weight of each animal (Table 1:p>0.05). Semen parameters in all the treatment groups (Groups B and C) decreased when compared with the control group. Only a minimal decrease was observed in the percentage sperm motility of the treated groups, and in the percentage of morphologically normal spermatozoa of the low dose group (Table 2). The percentage of normal spermatozoa was markedly reduced in the animals exposed to 1000 mg/kg/d (high dose) of garlic (69.00 ± 1.22) compared with animals that received a lower dose of 500 mg/kg/d (85.50 ±1.66) and the control animals (86.25 ± 1.75) given distilled water. There was a decrease in sperm motility in the treatment groups (Control: 92.17±0.66; Low dose group: 90.87±0.76; High dose group:90.27±1.13), but this was not statistically significant (p>0.05). Sperm concentration decreased in the treated groups with the animals treated with 1000 mg/kg/d aqueous garlic extract having the lowest value (63.85 ± 3.03) compared with those that received 500 mg/kg/d of the extract (65.35 ± 3.13) and the control group (72.15 ±0.74) that received distilled water. Superoxide dismutase enzyme was markedly reduced in the low dose group (279.75 ± 05.02 IU/ml; p<0.05) compared with the control animals (490.00 ± 20.10 IU/ml), with a much more decreased activity in the group that received a higher dose of 1000 mg/kg/d (188.00 ± 09.82 IU/ml; p<0.05).

Figure 1

Table 1: Weight Of Testes Following Administration Of Extract

Figure 2

Table 2: Semen Parameters and SOD activity

Discussion

The effects of garlic on male gonads, and by extension, the male reproductive function, may appear somewhat different from the usual cytoprotective activities observed by various workers in other tissues and organs of the body^19,3; although, the amount of garlic administered, to some extent, could be a factor¹². Administration of garlic augments the activities of SOD and also protects the cells against the damaging effects of free radicals, as given by some biochemical and histopathological evidences³. However, on the testes, use of garlic has been noted to compromise some male reproductive functions, as it affects spermatogenesis and testosterone levels, which are vital to reproduction¹¹.

Both at a lower and higher doses of garlic extract, the activity of SOD was noted in this study to decrease with increasing dosage. The endogenous antioxidative functions of the enzyme was compromised, thereby predisposing the cells of the testes to the detrimental effects of various oxygen radicals and other chemically-induced oxidative stress. In this study, both the percentage morphology and sperm count were significantly reduced, although sperm motility was only slightly reduced. Irrespective of the motility, in the event of increasing number of abnormal spermatozoa morphologically, spermatogenesis and other reproductive capability of an intact spermatozoon, could still be compromised. This is because previous studies have shown that use of Allium sativum is associated with increased percentage of empty seminiferous tubules and consequent reduction in testosterone secretion and altered spermatogenesis. The effects of garlic on semen parameters may not be unconnected to the suggested mechanism of apoptosis¹¹.