| Hawthorn (Crataegus) was used for both medicinal materials and edibles in China, and was a very important botanic resource. Many studies indicate that hawthorn has many active compounds and pharmacological effects. Our previous research showed that the main active compounds in Chinese hawthorn fruit is the OPC, include epicatechin and their polymers. Meanwhile we have found the existence for the first time of eucomic acid which are a flavor composition in hawthorn. Based on the previous studies, this paper has completed the following research work:(1) An analytical method for the determination of eucomic acid in hawthorn fruit and their products by gas chromatography-mass spectrometry (GC-MS) was developed. Samples of hawthorn or their products were extracted with ethanol absolute and etherified in 12% H2SO4-CH3OH, followed by separated on a HP-5MS column and analyzed by GC-MS for qualitative and quantitative. The oven temperature was programmed from 60℃(held for 1 min) to 160℃at 20℃/min (held for 1 min) and finally to 250℃at 20℃/min (held for 3 min). Helium was used as carrier gas at a constant flow rate of 1 mL/min. One microliter of samples was injected in split injection mode (20:1) at an injector temperature of 250℃. Electron ionization (EI) mode was used with electron energy of 70 eV. Transfer line, MS quad and MS source were maintained at 250, 150 and 230℃, respectively. In these conditions, the retention time of eucomic acid was 12.00 min, in the meantime, the average recovery and standard debiation of method was 87%~102% and 3.1%~5.6%, respectively. Method limits of quantification (LOQ) was 0.7μg.The GC-MS method was applied to the determination of eucomic acid in hawthorn and their products. Hawthorn fruit (255 mg/kg FW), hawthorn jam (7.2 mg/kg), two hawthorn juice (17.9 and 15.4 mg/kg, respectively), hawthorn soup (5.1 mg/kg) and hawthorn jelly (7.8 mg/kg). The results shown that the content of eucomic acid was obviously lower in the hawthorn products than the fruit, therefore, we consider that the eucomic acid can be regarded as an important index for quality assessment of hawthorn products. Not only will this index contributes to the quality assessment of hawthorn products, but also provides a guidance to the hawthorn processing in order to maintain the effective ingredients of hawthorn products as much as possible.(2) The free radical scavenging capacity (RSC) of five flavanols from Chinese hawthorn fruit was studied using DPPH·method. The EC50 values of five flavanos were 1.4 ~ 1.7 mg/L, and lower than other antioxidants (VC, Trolox, TBHQ and lipophilic tea polyphenols). The higher the degree of polymerization of flavanols, the stronger the RSC was. Moreover, different link type between flavan-3-ols has different RSC: procyanidin B5 was stronger than procyanidin B2. To understand the kinetic behavior better and to determine the RSC of flavanols, the second-order constant (k2) was calculated for quenching reaction with DPPH·radical. The k2 values for five flavanols were procyanidin D1 > procyanidin C1 > procyanidin B5 > procyanidin B2 > epicatechin.The antioxidant effect of hawthorn flavanol extracts for oils shown that it was an effective antioxidant with dose-dependent for oils. The larger the dose, the better the antioxidant effect is. 0.1% hawthorn flavanol extracts was equally effective with 0.02% TBHQ. VC, citric acid, and lipophilic tea polyphenols exhibit synergism for the antioxidant of hawthorn flavanol extracts. The utilization of Natural antioxidant is a tendency of food industry, and it will be applied widely in future. |
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