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Chemia i aktywność biologiczna czosnku (Allium sativum)

Kwiecień H.

Wiadomości Chemiczne

2008

[Z] 62, 9-10

901-942

Garlic (Allium sativum) has historically been one of the most common vegetables to serve as a both spice and medical herb in many countries. One of the outstanding features of the chemical composition of garlic is the large amount of unique organosulfur compounds, which provide its characteristic flavor and odor and most of its potent biological activity. Two classes of primary organosulfur compounds are found in whole garlic cloves: γ-glutamyl-S-alk(en)yl-L-cysteines and S-alk(en)yl-L-cysteine sulfoxides (alliin, metiin, propiin, isallin) (Fig. 1, 2) [5-15]. When garlic is crushed or cut, S-alk(en)yl--L-cysteine sulfoxides are exposed to the enzyme alliinase and thiosulfinates, via intermediate sulfenic acids are formed (Fig. 6) [29-33]. The major thiosulfinate, allicin is a reactive intermediate species that can be transformed, into a variety of compounds including diallyl, methyl allyl and mono- di-, tri-, tetrasulfides, vinyldithiins and ajoenes (Fig. 7-9) [37-49]. Garlic belongs to the Allium species, which accumulate only fructans as their nonstructural carbohydrates [52-59]. Garlic is also known for its production of some unique furostanol saponins, e.g. proto-eruboside-B and sativoside-B1 (Fig. 10-12) [60-63]. The Allium species also contain high levels of flavonides, including apigenin, myricetin and quercetin (Fig. 13) [64, 65], moderate levels of vitamins as well as free amino acids (Arg, Gln, Asn, Glu, and Lys) [66-69]. It was found that the amino acid fraction of Aged Garlic Extract (AGE) contain Maillard reaction products, N-fructosyl glutamine (Fru-Glu), Nα-(1-deoxy-D-fructos-1-yl)-L-arginine (Fru-Arg) (Fig. 14, 15) [74-76], as well as tetrahydro-?-carboline derivatives (Fig. 16, 17) [77-82]. Recently, allixin (Fig. 18), a novel phytoalexin, with the structure 4H-pyran-4-one, as a novel substance with neurotrophic activity has been reported to by synthesized by garlic [83-85]. Garlic has the ability to accumulate the selenium from soil and the major selenium compound in both Se-enriched and unenriched garlic was identified as γ-glutamyl-Se-methyl selenocysteine along with lesser amounts of Se-methyl selenocysteine, selenocysteine, selenomethionine among other compounds (Fig. 19) [86-96]. Pharmacological investigations have shown that garlic has a wide spectrum of actions, not only it is antimicrobial [97], but it also has beneficial effects in regard to cardiovascular and cancer diseases [2, 3, 14, 42]. A number of organosulfur substances derived from garlic such as allicin, allicin-derived organosulfur compounds including sulfides, ajoene, steroidal saponins, flavonides, Fru-Arg, Fru-Glu, organic seleno-compounds and tetrahydro-?-carboline derivatives have been found to have strong antioxidant properties. It has been suggested that garlic can prevent cardiovascular disease, inhibit platelet aggregation, decrease the synthesis of cholesterol and prevent cancer. Thus it may either prevent or delay chronic diseases associated with aging.