The stability of gingerol and shogaol in aqueous solutions.
Gingerols, pungent principles of ginger (the rhizome of Zingiber officinale), are biologically active components that may make a significant contribution towards medicinal applications of ginger and some products derived from ginger. Gingerols, however, are thermally labile due to the presence of a beta-hydroxy keto group in the structure, and undergo dehydration readily to form the corresponding shogaols. This study investigated the stability of [6]-gingerol [5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)decan-3-one] at temperatures ranging from 37 to 100 degrees C in aqueous solutions, at pH 1, 4, and 7. Quantitative measurements of [6]-gingerol and its major degradation product [6]-shogaol [1-(4-hydroxy-3-methoxyphenyl)decan-4-ene-3-one] were performed by HPLC. Kinetics of [6]-gingerol degradation was characterized by least square fitting of a rate equation. It was found that gingerol exhibited novel reversible kinetics, in which it undergoes dehydration-hydration transformations with shogaol, the major degradation product. Degradation rates were found to be pH dependent with greatest stability observed at pH 4. The reversible degradation of [6]-gingerol at 100 degrees C and pH 1 was relatively fast and reached equilibrium within 2 h. Activation energies for the forward and reverse reactions for [6]-gingerol were calculated from the Arrhenius equation using reaction rates obtained at temperatures ranging from 37 to 100 degrees C.
Bhattarai
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Faculty of Pharmacy, University of Sydney, NSW 2006, Australia.
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Duke
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D002396:Catechols / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism*; D004355:Drug Stability; D005233:Fatty Alcohols / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism*; D020939:Zingiber officinale / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010936:Plant Extracts / Q000737:chemistry; D012996:Solutions; D014867:Water / Q000737:chemistry
D002396:Catechols; D005233:Fatty Alcohols; D010936:Plant Extracts; D012996:Solutions; D014867:Water; C040115:shogaol; C007845:gingerol