Most of the medicinal effects of garlic are referable to sulphur compounds thiosulphinates and sulphides, products of conversion of allin from garlic by enzyme allinase. Allicin (diallyl thiosulphinate), the main thiosulphinate from garlic (Allium sativum L., Alliaceae), has been shown to be responsible for the antimicrobial, antiprotozoal, antimutagenic, antiplatelet and antihyperlipidemic effects of garlic. Diallyl sulphide, one of the degradation compounds of allicin, was identified as a suppressing agent in the dimethylhydrazine - induced colon cancer developed in rats. In addition, immunomodulatory properties of the garlic have been attributed to this sulphide component.

In our studies the correlation between the biological effects and variation in garlic components thiosulfinates and ajoenes were analysed. Two different garlic powders were investigated. Reversed-phase HPLC/UV and HPLC/DAD were used to separate thiosulfinates and quantification of allicin (methanol/water/formic acid = 40:60:0.1, 254 nm), and ajoenes prepared by 24 hour incubation of aqueous and ethanol extract of garlic (acetonitrile/water/tetrahydrofuran = 70:27:3, 240 nm). Pure allicin was isolated by TLC (Kiesel-gel 60 F 254, hexane/ethyl acetate = 60:40) after extraction from an aqueous solution from commercial garlic powder.

A comparison of two powders revealed the differences in contents of allicine, other thiosulfinates and ajoenes indicating the importance of analysis of products used for clinical investigation.