Garlic as a functional food I. Koca1 and B. Tasci2,a 1Faculty of Engineering, Dept. of Food Engineering, 55139, Ondokuz Mayıs University, Samsun, Turkey; 2Samsun Health High School, Dept. of Nutrition and Dietetics, 55139, Ondokuz Mayıs University, Samsun, Turkey.
Abstract Garlic has been used, for thousands of years both as a food and for medicinal purposes. Garlic can be used as a food preservative to inhibit the growth of pathogens and as a remedy for the treatment or prevention of a number of diseases. The purported health benefits of garlic are numerous, including, anticarcinogenic, antibiotic, anti-hypertensive, and cholesterol-lowering properties, the risk of cardiovascular disease lowering the effects of hypolipidemic, antithrombotic, antidiabetic, and anti-hyperhomo cysteinemia and, antioxidant, antimicrobial, immunomodulatory, antiasthmatic, antimutagenic, and prebiotic activities. The biologically active substances of garlic can be divided into two main groups; sulphur compounds and sulphur-free active substances. The main sulfur compounds are allicin and alliin. Allicin is the most biologically active compound of garlic. Allicin is not present in raw garlic, but it is rapidly produced by the action of allinase on alliin. Allinase is activated by crushing or chopping, garlic cloves. Allicin exhibits hypolipidemic, antiplatelet, and procirculatory effects and includes antibacterial, anticancer and chemopreventive activities. The group of sulphur-free active substances includes flavonols, antibiotics garlicin, allistatin, adenosine, sapogenins, and saponin. The biological effects of additional constituents of intact garlic, such as lectins, prostaglandins, adenosine, pectin, vitamins B1, B2, B6, C and E, biotin, nicotinic acid, glycolipids, fatty acids, phospholipids and essential amino acids, are well known and the importance of pharmacological activities, such as antifungal, antibacterial antitumor, anti-inflammatory and hypocholesterolemic properties of certain steroid saponins and sapogenins has recently been recorded. Also, garlic is rich in fructooligosaccharides. Fructooligosaccharides are types of prebiotics. Fructooligosaccharides contribute to the reduction of risk of many diseases. They have functional properties, such as improving blood parameters, enhancing resistance against intestinal, as well as extra-intestinal pathogens, modulating immune responses, and decreasing allergies. In this paper, the bioactive compounds of garlic and it’s physiological role on human health have been discussed. Keywords: garlic, preobiotic, functional foods, health INTRODUCTION Foods which yield health benefits apart from fundamental nutrition as a result of physiologically active food components are called functional foods (Hasler et al., 2000). By advancing the immune system and preventing diseases and degenerative disorders, functional foods produce physiological or metabolic advantages (Peshev and Van den Ende, 2014). “Functional food” have some particular characteristics such as being a traditional food or common food taken as part of the normal/usual diet; being made of natural (not synthetic) constituents occasionally in raised concentration or being existent in foods that would not typically supply them; having positive effect as well as nutritive value/basic nutrition which may increase well-being and health and/or decrease the risk of disease or bring health benefit in order to enhance the quality of life which includes psychological, physical and behavioral performances; and, having claims which are scientifically based (Roberfroid, 2002). Functional foods can be listed as: (a) common foods which have a
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Acta Hortic. 1143. ISHS 2016. DOI 10.17660/ActaHortic.2016.1143.20 Proc. VII Int. Sym. on Edible Alliaceae Ed.: A.F. Gokce
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bioactive substances that naturally occur (e.g., dietary fibre), (b) foods which are supplemented with bioactive substances (e.g., probiotics, antioxidants), and (c) derivative food ingredients which are added into traditional foods (e.g., prebiotics) (Al-Sheraji et al., 2013). Garlic (Allium sativum) is a functional food (Hasler et al., 2000). For thousands of years, it has been used for a great many different medicinal purposes and its effects can be attributed to its diverse physiologically active organosulfur components (Hasler, 2002). It has been reported that organosulfur components of garlic employ numerous physiological effects, such as hypocholesteremic activity, antithrombic effect, inhibition of platelet aggregation, antimicrobial activity, lipid-lowering effect, hypoglycemic activity, and lipoxygenase and tumor inhibition (Rodriguez et al., 2006). Clinical studies have shown garlic to have a moderate blood pressure-lowering effect and an inverse relationship has been reported between garlic consumption and certain types of cancer, especially stomach cancer, by an increasing number of epidemiologic data (Hasler, 2002). COMPOSITION OF GARLIC About 200 active substances are found in garlic including proteins, carbohydrates, vitamins, amino acids, individual chemical elements (macro-and micronutrients-calcium, phosphorus, sulfur etc.) and enzymes (Bordea et al., 2013). Fresh garlic has two main groups of biologically active substances: (a) sulphur compounds and (b) sulphur-free active substances. Sulphur compounds are very important flavor compounds and allicin, alliin, and ajoene are in this group. Sulphur-free active substances are substances such as allistatin, adenosine, sapogenins, anthocyanins, flavonols, antibiotics garlicin, and saponins (Gré grová et al., 2013). SULPHUR-CONTAINING COMPONENTS OF GARLIC Alliin (S-allyl cysteine sulfoxide) can be found in amounts of 5-14 mg g-1 of garlic. It is a precursor of allicin and it is odorless. It restricts collagen-induced platelet aggregation in human platelet-rich plasma (Agarwal, 1996). Allicin (allyl 2-propenethiosulphinate or diallyl thiosulphinate) is thought to be the main bioactive compound of raw garlic. Chopping or crushing raw garlic activates allinase enzyme and acts on alliin (present in intact garlic) to produce alicin (Banerjee et al., 2003; Baghalian et al., 2005). Allicin is known to have a great number of biological effects such as antimicrobial, anti-inflammatory, antithrombotic, anticancer, and antiatherosclerotic activities besides the capacity to lower serum lipid levels and ocular pressure. Its strong SHmodifying and antioxidant features are thought to be responsible for most of these effects (Miron et al., 2002). Pure allicin was reported to show antibacterial activity against an extensive variety of Gram-negative and Gram-positive bacteria, such as multidrug-resistant enterotoxicogenic strains of Escherichia coli; antiparasitic activity, which includes some major human intestinal protozoan parasites like Entamoeba histolytica and Giardia lamblia; antifungal activity, especially against Candida albicans; and antiviral activity. Allicin’s chemical reaction with thiol groups of various enzymes such as alcohol dehydrogenase, thioredoxin reductase, and RNA polymerase which can affect essential metabolism of cysteine proteinase activity involved in the virulence of E. histolytica is the reason for its antimicrobial effect (Ankri and Mirelman, 1999). Through a thiol-disulfide exchange reaction, allicin reacts very rapidly with free thiol groups (Miron et al., 2002). Allicin has been shown to be rapidly metabolized (half-life,
