Stability and Decomposition Products of Allicin in the Aqueous Solution

Abstract:

The stability of allicin in an aqueous solution is extremely important for the processing of garlic products. In this paper，the effects of temperature，concentration and pH value on the stability of allicin were investigated. Results show that the higher the temperature and concentration，the lower the stability of allicin in the aqueous solution. When temperature was relatively low or allicin concentration was high，decomposition products of allicin tended to be ring compounds such as 3-vinyl 1，2-disulfide cyclohex-4-ene and 3-vinyl 1，2- disulfide cyclohex-5-ene；conversely，the products primarily contained straight-chain compounds such as diallyl disulfide. The stronger the solution acidity was，the more stable allicin became. For this phenomenon，hydrogen bonding interaction of allicin with deuterated acetic acid was characterized by NMR. Theoretical calculations found that the main bond length between O（13） and H（5） of allicin obviously elongated and the molecular energy decreased in the protonated acid solution，which revealed the mechanism for the higher stability of allicin in an acidic solvent.