THE ROLE OF ALLIUM SATIVUM (GARLIC) IN VARIOUS DISEASES AND ITS HEALTH BENEFITS: A COMPREHENSIVE REVIEW

B. J. Divya 1 , B. Suman 2 , L. Lakshman kumar 2 , M.Venkataswamy 2 , B. Eswari 2 and * K. Thyagaraju 2 . 1. Department of Biochemistry& Academic consultant pharmacy, Sri Venkateswara University, Tirupati 517502. 2. Department of Biochemistry, Sri Venkateswara University, Tirupati 517502. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

It is used as medicine in the treatment of heart diseases, tumours, headaches and exhibits medicinal properties including immunomodulation, hepatoprotection, antioxidant, antimutagenic, antibacterial and anticarcinogenic effects (Agarwal 1996). Moreover, it has also been reported to possess antifungal (Halliwell et al., 1992), hypoglycemic (Yoshida et al.,1987), hypolipidemic, anti-atherosclerotic properties (Bordia, 1981) antidiabetic, antithrombotic, and antihypertensive, (Banerjee and Maulik 2002) and has been claimed to be effective against a number of diseases (Block et al., 1984) (Table 2).  Tariq et al., 1988 On the other hand, garlic is an herbal medicine which is used for prevention and treatment of many diseases such as diabetes, thrombosis and hypertension. A health property of garlic depends upon the bioactive compounds especially 595 the organosulfur compounds (Rahman, 2007;(Tepe et al., 2005), which are also responsible for the pungent flavor of garlic. Phenolic compounds are large groups of secondary metabolites that are able to neutralize or quench the free radicals (Picchi et al., 2012). Flavonoids and their derivatives are the largest group of polyphenols found in plants (Hounsome et al., 2009).

Anti fungal nature of garlic:-
In-vitro studies proved that garlic extract inhibited the growth of a large number of yeasts including Candida spp. and fungi such as Coccidioides immitis (Adetumbi et al., 1986;Appleton & Tansey 1975; Barone & Tansey 1977;) and dermatophytic fungi T. rubrum, T. mentagrophytes, T. verrucosum, Microsporum canis and Epidermophyton flocossum (Aala et al., 2010). Fresh aqueous garlic extract showed antifungal activity specifically against A. fumigates, A. terreus, A. nidulans and A. niger (Pai & Platt 1995). The activity of allicin against Trichophyton spp. is better than essential oils (biological compound) from Allium plants (Pyun & Shin 2006). Ajoene is an active compound found in garlic which plays a great role as topical antifungal agent. Garlic has been shown to inhibit growth of fungal diseases as equally as the drug ketoconazole, when tested on the fungi Malassezia furfur, Candida albicans, Aspergillus, Cryptococcus, pencillium funiculosum, trichoderma brevicompactum and other Candida species.

Antibacterial activity of garlic:-
The antimicrobial activity of garlic and garlic-derived organosulfur compounds was widely investigated against both food spoilage bacteria and food-borne pathogens (Leuschner and Ielsch 2003). Garlic inhibited the growth of 20 different strains of Mycobacterium avium intracellulare isolated from AIDS patients and non-AIDS patients (Deshpande et al., 1993). Garlic  The antimicrobial effects of equivalent concentrations of garlic derivatives were seen in ground camel meat. The addition of either garlic or butylated hydroxyanisole (BHA) significantly delayed lipid oxidation when compared with the control. The antioxidant activities of the various ingredients added followed the order of fresh garlic (FG), garlic powder (GP), BHA, and garlic oil (GO) were studied. The results suggested that fresh garlic and garlic powder, through their combined antioxidant and antimicrobial effects, are potentially useful in preserving meat products (Hamid et al., 2012).

Antimicrobial and Anti-proliferative activity:-
Garlic is nicknamed Russian penicillin for its widespread use as a topical and systemic antimicrobial agent (Agarwal 1996). The antimicrobial properties of garlic were first described by Pasteur (1958) by its activity against many species of bacteria, viruses, parasites, protozoan and fungi (Jaber and AlMossawi 2007).
Anti-proliferative activity of ajoene was demonstrated against a panel of human tumor cell lines (Li et al., 2002). Supercritical CO 2 extraction of garlic oil is done to effectively extract heat sensitive, easily oxidisable, volatile substances like allicin which explore the inhibitory effect on human hepatoma HepG2 cell growth. Human hepatoma HepG2 cells were cultured in vitro, and changes in growth of allicin-treated HepG2 cells were determined by MTT assay and flow cytometry (Hailin et al., 2016).
Ajoene, isolated from extracts of garlic may inhibit adhesive interaction and fusion of leukocytes (Tatarintsev et al., 1992). Antiviral activity of garlic in humans may be secondary to a direct toxic effect on viruses. It also enhanced NK-cell (Natural killer-cell) activity that destroys virus-infected cells (Tariq et al 1988).
Antiparasitic and Anti-protozoal properties:-Many folks healers and herbalists world wide recommend garlic as a treatment for intestinal parasites. In some cultures, children infested with helminths are treated with enemas containing crushed garlic (Weiss 1988). Allicin exhibits antiparasitic activity against major human intestinal parasites such as Entamoeba histolytica, Ascaris lumbricoides and Giardia lamblia (Ankri and Mirelman 1999). Many herbalists worldwide recommend garlic as a treatment for intestinal parasites (Pankaj Kashyap et al., 2016).

Antioxidant principle of garlic:-
The strong antioxidant effect of garlic extract has also recently been claimed to prevent cancer, thrombus formation, cardiovascular disease and some diseases. The antioxidant potential of garlic in vivo and in vitro has been proved (Jackson et al., 2002). Biochemical studies have demonstrated that garlic extract (GE) acts as antioxidants to protect cells against reactive oxygen species (ROS) (Chung 2006). Some previous studies have shown that garlic extract or some of its components may have potential anti-aging effects (Powolny et al., 2011). The antioxidant effect of garlic and aged black garlic was studied in animals. The antioxidant activity of garlic and aged black garlic was measured as the activity in scavenging free radicals by the trolox equivalent antioxidant capacity (TEAC) assay Consumption of aged black garlic significantly decreased hepatic thiobarbituric acid reactive substances (TBARS) level. The SOD, GSH-Px, CAT) activity of aged black garlic group was increased (Young-Min et al., 2009). Aged black garlic recently available on the market in Korea is one of the garlic products expected to have strong antioxidant capacity. It is produced by ageing whole garlic at high temperature (70 o C) and high humidity (90% RH) (Jang et al., 2008;Kang et al., 2008).
Garlic extract showed 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (Querioz et al 2009) and superoxide dismutase (SOD) activity in vitro (Jang et al., 2008). in vivo in the generation of reactive oxygen species (ROS) by heavy metals, which initiates lipid peroxidation, thereby causing oxidative damage to critical macromolecules like proteins, DNA as well as cell damage/ death (Das et al., 2001).The effect of coadministration of garlic and ezetimibe on biochemical factors and antioxidant activity in hypercholesterol mice were tested. The activity of SOD, CAT and GSH levels were markedly increased in garlic and ezetimibe and combination of garlic and ezetimibe groups compared with hypercholesterole mice (Abbas Mohammadi et al., 2014).The effect of garlic on the liver phosphatidate phosphohydrolase (PAP) activity, plasma lipid levels, malondialdehyde (MDA) and plasma antioxidant in rats fed either by normal or high-lipogenic diet with or without garlic lipogenic diet, Results showed that garlic significantly reduced (TC, TG, LDL-C, VLDL-C, liver triglyceride, MDA and plasma antioxidant in garlic treated rats (Esfandiar Heidarian et al., 2011).
The effect of Garilc Powder on feeding performance, digestibility, blood lipid profile, digestive organs and carcass cuts of broiler chickens was studied. COL, TG, HDL, LDL levels were determined. Results of this study showed that Garilc Powder had no significant effects on broilers weight gain, feed intake (FI), feed conversion ratio (FCR), carcass cuts, visceral organs. How-ever, garlic powder decreased COL, TG, LDL and increased HDL levels compared to control birds. The dry matter (DM), crude protein (CP) and ether extract (EE) digestibility were improved by feeding Garilc powder (Kamal Jamal 2012). The effect of raw garlic on patients suffering from alcoholic liver disease was studied. Blood samples were collected and the liver disease was measured by the 597 activities of liver marker enzymes (AST, ALT, ALP, GGT and LDH) which were elevated in alcoholic patients. Increased lipid peroxidation in alcoholic patients was accompanied by decreased activities of SOD, CAT, GPx. significantly lowered the activities of liver marker enzymes(Sankaran Mirunalini et al., 2010). Garlic extract exerts antioxidant action by scavenging reactive oxygen species ROS, enhancing the cellular antioxidant enzymes; SOD, CAT and Gper and increasing glutathione in the cells. Garlic inhibits lipid peroxidation, reducing ischemic/reperfusion damage and inhibiting oxidative modification of LDL. Garlic protects DNA against free radical-mediated damage and mutations (Carmia 2001). Gentamicin (GM) nephrotoxicity has been related to oxidative stress. Garlic and metformin (MF) have antioxidant activity and therefore, this study against curative effects of garlic, MF and their combination on GM induced tubular toxicity in Wistar rats was done. The results indicate that MF and garlic or their combination have curative and protective activity against GM nephrotoxicity.
Immunomodulatory effect of garlic:-Garlic has probably been most popularized as a complementary therapy for blood pressure control, as it is used by approximately 50% of patients who have hypertension (Capraz et al., 2006). Recent in vitro studies by Benavides et al., (2007) have confirmed the vasoactive ability of garlic's sulfur compounds. Aged garlic extract contains the active and stable component S-allylcysteine, which allows standardization of dosage (Lawson and Gardner 2005) In isolated strips of canine carotid arteries and in isolated rat aorta, garlic exerted direct vasodilating effects (Ozturk et al., 1994) Garlic also activates the synthesis of nitric oxide, which is a potent endogenous vasodilator (Das et al., 1996).
The effects of processed garlic (PG) on the systolic blood pressure (SBP) and the diastolic blood pressure (DBP) of spontaneously hypertensive rats (SHR) and on the BP of hypertensive humans was significant, DBP reduction was also found in the placebo group , which might be attributed to a placebo effect. After 8 weeks, PG lowered SBP. In conclusion, it had significantly lowered blood pressure in hypertensive subjects (Chuan-Hsiao et al., 2011).
Endothelial NOS (eNOS) derived NO induces relaxation of vascular smooth muscle cells leading to vasodilatation via guanylyl cyclase dependent mechanism (Forstermann and Sessa 2012). The antihypertensive properties of garlic have been linked to stimulation of intracellular nitric oxide and hydrogen sulphide production, and blockage of angiotensin II production, which in turn promote vasodilation and thus reduction in Blood Pressure (Castro et al., 2010). The study was investigated the effect of consumption of garlic powder on blood pressure and renin angiotensin system in a nitric oxide deficiency hypertension model in male rats. After different doses of injection of angiotensin I and angiotensin II, mean arterial pressure was significantly increased in the normotensive-garlic and the hypertensive-garlic groups, respectively Garlic powder consumption has reduced blood pressure, it did not have an effect on the interaction between renin angiotensin system and nitric oxide inhibition. (Aliasghar Vahidinia et al., 2015 ).

Inhibitory effect on cardiac arrest:-
Garlic and its derived compound ajoene have demonstrated inhibition of platelet aggregation in vitro as well as in experimental animals and reduction of platelet dependent thrombus formation ( Shah et al., 2014).Studies have shown that garlic has great potential in inhibiting platelet aggregation and enhancing fibrinolytic activity (Sogani and Katoch 1981). Recent in vitro studies have confirmed the vasoactive ability of garlic's sulfur compounds, where by red blood cells convert garlic's organic polysulphides into hydrogen sulphide, a known endogenous cardioprotective vascular cell-signaling molecule (Benavides et al., 2007).
Joshua Adamu et al., 2014 investigated liver function profile, hematological and biochemical effects of garlic, the liver histology revealed evidence of distorted cyto-architecture of the liver cells in animals treated with combination of garlic. The hematological parameters were tested in rats fed by giving garlic as a juice for 30 days significantly, increased the red cell count, haemoglobin concentration and the PCV when compared with the control. Also garlic fed rat showed a significant increase in total white blood count, neutrophils, monocytes and the lymphocytes. No significant changes were observed in the basophil and eosinophil counts of animal fed with garlic, when compared with control (Iranloye 2002). The effect of feeding garlic powder (GP) on the performance, digestibility, digestive organs, carcass cuts and lipid profile of broilers Cobb-500 chicks were seen, Blood samples from 3 birds per replicate were collected on 3rd, 5th and 6th week post feeding from wing vein for blood lipid profile determination. COL, TG, HDL, low density lipoprotein (LDL) were determined. Results showed that GP had no significant effects on broilers weight gain, feed intake (FI), feed conversion ratio (FCR), carcasscuts, visceral organs. However, GP 598 decreased COL, TG, LDL and increased HDL levels compared to control birds. The dry matter (DM), crude protein (CP) and ether extract (EE) digestibility were improved by feeding GP ( Kamal Jamal and Abo Omar 2012).

Anti cancer activity of garlic:-
The anticancer effect of diallyltrisulfide in human colon cancer cells HCT-15 and DLD-1 was due to disrupted microtubule network formation of the cells. There are several prognostic biomarkers like nuclear receptors whose over-expression is associated with Breast cancer characteristics. These biomarkers can be blocked by compounds with anti-cancer potential by the Docking studies and ADMET evaluation revealed twelve compounds to be active against the targets (Nabarun Roy et al., 2016). The cytotoxic activities of the ethanolic extract of bulb of Allium sativum against human cancer cells was determined by SRB assay. A comparative study was done with two other Cell Line namely Central Nervous System Cell Line and Colon Cancer Cell Line. The cytotoxic activity shown by the ethanolic extract of Allium sativum against Colon cancer cell line was more when compared to that of CNS cell line. (Ekta Prakash et al., 2016). The anti-proliferative effect of allicin was analysed on human hepatoma HepG2 cells using MTT assay and flow cytometry in order to provide data support for its clinical application. Allicin has a marked inhibitory effect on HepG2 cell growth; moreover HepG2 cell inhibition rate increases with increasing allicin concentration and treatment time (Hailin et al., 2016).
The effect of garlic oil (GO), alone or combined with low dose total body gamma (γ)-irradiation (LDR) against paracetamol (APAP)-induced hepatotoxicity was investigated in rats. GO oral administration for 14 days, LDR irradiation for 2 hours were done prior to hepatotoxicity induction by peroral APAP administration. Then the rats were sacrificed 24 hours later. GO alone or combined with LDR, ameliorated APAP-induced adverse effects which was revealed by the reduction of serum liver marker enzymes activities and the histological examination . It could thus be concluded that the hepatoprotective activity of GO and LDR and their anti-oxidant and anti-apoptotic actions could be of beneficial value in the protective management of excessive hepatic damage induced by APAP hepatotoxicity. (Rasha et al., 2014). Aged garlic extract (AGE), increases natural killer (NK) cell activity. In addition, animal studies have shown that AGE induces the release of cytokines such as IL-2, TNF-α and INF-α (Kyo et al., 1998). These effects suggest that AGE, stimulates a Th1 cellular immune response that is characteristic of effective antitumor immunotherapies. Sundaram and Milner (1996) has reported that DADS was as effective as 5fluorouracil (a potent anti-cancer drug) in inhibiting growth of tumors in transplanted human colon carcinoma cells.

Anti diabetic activity of garlic:-
The use of garlic as a folk medicine for diabetes has been reported in Europe (Mathew and Augusti, 1973) in India (Grover et al., 2002) and in the Middle East (Bailey and Day 1989). Recent studies have directed their efforts towards the protective effects of plants such as garlic on hyperlipidemia (Ortega et al., 2007). Garlic oil significantly decrease the levels of antioxidant ceruloplasmin, albumin and total thiols in the plasma of diabetic rats but SOD activities was decreased in tissue homogenates of liver and kidney (Mamdouh and Abdel-Raheim, 2003). Garlic has also been shown to have antioxidant properties, gastrointestinal neoplasias, against blood clots (anti-platelet action) due in part to the compounds alliin and ajoene, which have fibrinolytic activity (Metwally 2009) Most of the studies showed that garlic can reduce blood glucose level in diabetic mice and rabbits (Ohaeri, 2001) From a comparison study made between the action of garlic extract and glibenclamide, it was shown that the antidiabetic effect of the garlic was more effective than the glibenclamide (Eidi et al., 2006). Aqueous extract of garlic (500 mg/kg/d IP) increased total serum antioxidant levels in STZ-treated diabetic rats.
Alloxan diabetic rats with the antioxidant SACS isolated from garlic, controlled lipid Peroxidation and stimulated in vitro insulin secretion from B cells isolated from normal rats ( Augusti and Sheela 1996). Garlic extract attenuated hypoglycemia and structural nephropathy progression in streptozotocin (STZ)-induced diabetic rats (Al-Qattan et al., 2008). Consumption of diet containing 5% garlic powder significantly decreased serum glucose and total cholesterol in db/db mice, an animal model of type 2 diabetes. The anti diabetic effects of garlic were studied in alloxan induced diabetic male rabbits, compared to normal control and diabetic control male rabbits. The serum cholesterol level and body weight were also studied. the significant hypoglycaemic, hypocholesterolaemic and hypolipidaemic effects were shown. Therefore, study reinforces the findings of previous studies that garlic had a significant effect in reducing blood glucose (Mahesar et al., 2010) The hypoglycemic properties of the ethanolic extract of the bulbs of Allium sativum were evaluated in normol glycemic rats. The ethanolic extract of A. sativum bulbs reduced the blood glucose level after treatment in albino rats (Shakya et al., 2010).

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The potential immunomodulatory effect was shown by administration of allicin in the autoimmune disease process of type 1 diabetes the levels of anti-islet cell antibodies, Pan T lymphocytes marker (CD90), Pan B lymphocytes markers (CD19), and Pan innate cells marker (CD11b) were decreased in male rats with Streptozotocin-induced type 1 diabetes. The administration of allicin especially in high doses to the type1 diabetic rats leads to a significant decrease in the levels of all immunological parameters and stop the disease process (Muhamed Osman et al., 2016). The effect of garlic extract and glibenclamide on biochemical parameters, enzyme activities, and reduced glutathione content in the liver as well as on pancreas tissue in alloxan-induced diabetic rats were studied. These results suggest the potential of garlic extract as histo protective against free-radical-associated diabetes damage, preserving the ability of insulin secretion, and show a concentration-dependent antidiabetic effect(Lilia Douaouya and Noureddine 2016).

Conclusion:-
This review is useful to increase advanced knowledge on garlic therapeutic effects and improve our future experimental and clinical research plans. Several studies conducted on garlic have showed many health benefits and traditional uses worldwide over the centuries. Although it is shown that garlic may have a significant clinical potential either in their own right or as adjuvant therapy in different disorders. Garlic synthesizes series of sulfur compounds which shows multiple biological activities at nutrition and therapeutic level. Garlic contains organosulfur compounds which show cardiovascular, lipid-lowering effects, anti-platelet, hepatoprotective, antioxidant, anti diabetic, anti hypertensive, antiproliferative, anticancer, antioxidant, anti fungal, antimicrobial activity, anti parasitic and anti protozoal etc. It is rich in antioxidants which help, destroy free radicals that can damage cell membranes and DNA.
Because of its active principles role on health, garlic is attracting the interest of nutritionists, medicos, industrialists and business people.