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Free and Bound Volatile Compounds from Rocket, Eruca sativa (L.)

Rocket, Eruca sativa (L.) belongs to Brassicaceae family. It contains glucosinolates and O-glycosides. The glucosinolates and their aglucones are biological active compounds. Composition of the obtained aglucones depends on the structure of glucosinolates and degradation conditions such as pH-values, temperatures, Fe2+ ions and specific protein  1 . Further, chemical analysis of aglucones depends on the mode of isolation and concentration. The volatiles were isolated from fresh plant material of rocket (flowers, leaves and green beans) prior and after the autolysis  2 by two methods: simultaneous hydrodistillation-extraction and simultaneous hydrodistillation-adsorption, proposed method  3 . All isolates of volatiles were analyzed by GC and GC/MS. Isothiocyanates, nitriles, aliphatic alcohols, carbonyls, fatty acids, hydrocarbons, phenylpropane derivatives were identified. The major component in all isolates was 4-methylthiobuthylisothiocyanate. The volatiles which were isolated after the autolysis had larger number of compounds than the volatiles obtained without autolysis. The main advantages of hydrodistillation-adsorption method over hydrodistillation-extraction method are: the isolation is particular, higher yield, simultaneous separation of volatile isolate in three fractions (polar, non polar and light volatile compounds). O-glycosides of volatile compounds were isolated and purified by selective extraction and column chromatography from the same plant material. After hydrolysis of O-glycosides, using β -glucosidase, liberated volatile O-aglycones were also analyzed by GC and GC/MS. Compounds with sulphur and nitrogen (which are characteristic for glucosinolates) were not identified among these compounds. The main volatile O-aglycones were: 2-phenylethanol, benzyl alcohol, eugenol, (Z)-3-hexen-1-ol. Some of them were identified in volatile isolates together with the sulphur and nitrogen containing compounds, such as (Z)-3-hexene-1-ol, benzyl alcohol and 2-phenylethanol. The chemical composition of O-aglycones from rocket has not been reported, so far as we know.

Eruca sativa (Mill.); rocket; Brassicaceae; glucosinolates; hydrodistillation - adsorption; isothiocyanates; glycosydically bound volatiles; GC-MS.

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