2.4 Garlic (Allium sativum)
2.4.1 Introduction
Garlic (Allium sativum) is one of the oldest medicinal plants used by different cultures. Already in antiquity it was used for treatment and prevention of some diseases (Rivlin, 2001). Garlic is a member of the Alliaceae and is related to onions (Allium cepa), chives (Allium schoenoprasum) and ornamentals like star of Persia (Allium cristophii). Although many plants include “garlic” as part of their common names, only plants in the genus Allium with the specific epithet sativum are true garlics (Foster, 1996).
Many laboratory studies have confirmed garlic medicinal properties such as anticancer, antibacterial, antifungal, antivirus, immunostimulating, and antioxidant properties of garlic (Weisberger
Unlike oily sulfur compounds, water-soluble compounds are odourless and have more delicate and less characteristic flavour (Kodera et al., 2002). These compounds are also formed during aqueous garlic extraction, when the initial compound GSAC is transformed into SAC and this reaction is catalyzed by g-glutamyltranspeptidase (gGT). SAC along with its derivatives, S-methylcysteine (SMC) and SAMC are components of aqueous extracts of garlic and possess biological activity both in vitro and in
They have reported an inhibitory effect of DADS on growth of human colon tumour cells (HCT-15) implanted in nude mice. Studies from the laboratory of Singh et al. have shown that DADS suppressed growth of H-ras oncogene- transformed tumour xenografts in nude mice without any side effects (Singh et al, 1996). Similarly, DATS significantly inhibited growth of PC-3 human prostate cancer xenografts in male nude mice (Xiao et al., 2006).
All above-presented studies carried out on animal models suggest that garlic oil and oil-soluble organosulfur compounds (most of all allyl sulfides) are effective in affording protection against some types of cancer, mostly gastrointestinal, induced by a variety of chemical carcinogens.
Concerning in vivo studies, it may be doubtful whether all doses of allyl sulfides used in literature, apart from positive effects inhibiting cancer growth, indeed did not cause adverse side effects on normal cells. Some studies have suggested that normal cells were more resistant to apoptosis induction by OSCs compared with cancer cells (Karmakar et al., 2007; Kim et al., 2007). On the other hand, other studies have demonstrated toxicity of higher doses of fresh garlic extract in normal cells of the gastrointestinal tract (Nakagawa et al., 1980; Joseph et al., 1989).
2.4.4.2 Garlic anticancer activity