CJCU

Chem. J. Chinese Universities ›› 2017, Vol. 38 ›› Issue (9): 1549.doi: 10.7503/cjcu20170147

• Analytical Chemistry • Previous Articles     Next Articles

Spectroscopic Studies on Alkaline Autoxidation of Curcumin and Antioxidative Activities of the Product†

YANG Xin1, ZHANG Di2, SONG Limin1, XU Qian2, XU Hui2,3,4,*(), LIU Ke5   

  1. 1. School of Chemistry and Chemical Engineering, Yantai 264005, China
    2. School of Pharmacy, Yantai 264005, China
    3. Key Laboratory of Molecular Pharmacology and Drug Evaluation, Ministry of Education, Yantai 264005, China
    4. Collaborative Innovation Center of Advanced Drug Delivery System and Biotech Drugs in Universities of Shandong, Yantai University, Yantai 264005, China
    5. Suzhou Nanomedicine R&D Co. Ltd., Suzhou 215123, China
  • Received:2017-03-13 Online:2017-09-10 Published:2017-08-17
  • Contact: XU Hui E-mail:xuhui33@sina.com
  • Supported by:
    † Supported by the National Major Scientific and Technological Special Project for “Significant New Drugs Development” during the Twelfth Five-year Plan Period, China(No.2014ZX09301306-006) and 2017 Graduate Science and Technology Innovation Fund of Yantai University, China(No;YDYB1725)

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Abstract:

Curcumin is a natural antioxidant with strong biological and chemical activity. The curcumin degradation was carried out under weak alkaline conditions at room temperature, integrated used by means of column chromatography, UV, IR, NMR, MS and other spectral analysis techniques, the chemical structure of the major degradation products was isolated and identified. For the reaction process, the qualitative and quantitative studies were carried out from two aspects: substrate elimination and product formation by HPLC-DAD spectroscopy analysis technology. Ascorbic acid was used as a positive control, and its antioxidant activities were evaluated in vitro, by 1,1-diphenl-2-picrylhyrazyl free radical(DPPH·), hydroxyl radical(·OH) and superoxide radical(O2-·) scavenging assays, and compared with curcumin quantitatively. The results showed that the main degradation of curcumin at room temperature under weak alkaline conditions was autoxidation reaction, both of which conformed to the first order kinetics. the structure of heptadiene -3,5-diketone in curcumin[(1E,6E)-1,7-bis-(4-hydroxy-3-methoxy-phenyl)-1,6-heptadiene-3,5-dione] forms a quinone methide intermediate in the presence of alkaline environment, after a series of oxygenation, hydration, dehydration and rearrangement, the target compounds bicyclopentadiones was a cyclization product with a tetrahydrofuran ring and cyclopentanedione structure in the molecule, we named CURC[6-hydroxy-1-(4-hydroxy-3-methoxyphenoxy)-3-(4- hydroxy-3-methoxyphenyl)-1,3,3a,6a-tetrahydro-4H-cyclopenta[c]furan-4-one]. Based on the established stable and reliable spectrophotometric system, the results of in vitro free radical scavenging activity of CURC and curcumin are as follows. CURC has a certain scavenging activity on DPPH·, ·OH and O2-·, but the action intensity is significantly lower than that of curcumin. The EC50 values were 0.17 mmol/L and 0.022 mmol/L in the DPPH assay, 0.33 mmol/L and 0.098 mmol/L in the ·OH assay as well as 0.38 mmol/L and 0.056 mmol/L in the O2-· assay, respectively. The obtained results suggest that the pH condition should be strictly controlled during the application of curcumin and avoid the autoxidation reaction.

Key words: Curcumin, Alkaline autoxidation, Bicyclopentadiones, Antioxidant activity, Spectral analysis

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