Preparation of (+)-Trans-Isoalliin and Its Isomers by Chemical Synthesis and RP-HPLC Resolution

Abstract

Naturally occurring (+)-trans-isoalliin, (R(C)R(S))-(+)-trans-S-1-propenyl-L-cysteine sulfoxide, is a major cysteine sulfoxide in onion. The importance of producing it synthetically to support further research is very well recognized. The (+)-trans-isoalliin is prepared by chemical synthesis and reversed-phase (RP)-HPLC. First, S-2-propenyl-L-cysteine (deoxyalliin) is formed from L-cysteine and allyl bromide, which is then isomerized to S-1-propenyl-L-cysteine (deoxyisoalliin) by a base-catalyzed reaction. A mixture of cis and trans forms of deoxyisoalliin is formed and separated by RP-HPLC. Oxidation of the trans form of deoxyisoalliin by H2O2 produces a mixture of (-)- and (+)-trans-isoalliin. Finally, RP-HPLC is used successfully in separating (-)- and (+)-trans-isoalliin, and hence, (+)-trans-isoalliin is synthesized for the first time in this study. In addition, the (±) diastereomers of cis-isoalliin are also separated and purified by RP-HPLC.

Anti-cancerous/Anti-bacterial Activities of Allicin Generated In situ from Diastereo Pure Alliins by Alliinase

“…The yield was 76% (14.2 g) with purity of higher than 97%. The characterization data of the product were consistent with the literature results [22,[24][25][26].…”

“…The synthesis of compound 3 is a modified literature procedure which is based on earlier work by Iberl et al with precise temperature control throughout the reaction [22,23]. Lcysteine hydrochloride monohydrate (20 g, 0.11 mol) was dissolved in 20 mL of water and stirred in an ice bath; then, 20 mL of an aqueous solution of sodium hydroxide (16g, 0.4 mol) was added drop wise.…”

“…S-2-propenyl-L-cysteine sulfoxides were prepared by oxidation of the corresponding S-2propenyl-L-cysteines with hydrogen peroxide with quantitative yield following a procedure described previously which was based on earlier work by Yu et al [22,27] with modifications. To a 200 mL aqueous solution of compound 3 (7.67 g, 0.047 mol) at 0ºC, 5.4 mL of 30% H 2 O 2 (0.047 mol) was added drop wise.…”

Influence of different wild-garlic (Allium ursinum) extracts on the gastrointestinal system: spasmolytic, antimicrobial and antioxidant properties

“…The extensive analyses of the recorded 1D and 2D spectra, in two different NMR solvents, allowed a direct quantitation of six different sulphur‐containing compounds (three diastereomeric pairs): alliin and allo ‐alliin, trans ‐isoalliin and trans ‐ allo ‐isoalliin, as well as methiin and allo ‐methiin, differing in the configuration as the sulphur atom. Peak assignment was accomplished through detailed analyses of 2D NMR spectra, alongside a comparison with literature data . Specific signals of all mentioned amino acids were clearly resolved from all other signals, except in the case of alliin and its diastereomer, which were quantified from mutually overlapped multiplets, with the aid of spectral simulation (MestReNova 6.0).…”

“…Peak assignment was accomplished through detailed analyses of 2D NMR spectra, alongside a comparison with literature data. [21][22][23][24][25] Specific signals of all mentioned amino acids were clearly resolved from all other signals, except in the case of alliin and its diastereomer, which were quantified from mutually overlapped multiplets, with the aid of spectral simulation (MestReNova 6.0). Typical 1 H NMR spectra of A1-A5 are provided in the supplementary material ( Figures S6 and S7) file, along with the appropriate expansions.…”