Improved gas chromatography of amygdalin and its diastereomer

Separation and determination of amygdalin and unnatural neoamygdalin in natural food supplements by HPLC-DAD

This work is focused on separation and determination of amygdalin and its unnatural form neoamygdalin in natural food supplements. Reversed-phase high-performance liquid chromatography with a high-stability silica-based column with C₁₈ functional group has been used for solving this problem. The effect of the mobile phase composition as well as the column temperature on the separation of the amygdalin epimers has been investigated. Isocratic elution using a mobile phase composed of 0.05% aqueous formic acid and acetonitrile achieved the required separation within 17 min. Under optimum chromatographic conditions, the developed method was validated and was applied for the determination of amygdalin epimers in natural food supplements containing apricot or peach kernels. A simple extraction method using methanol as an extractant supported by an ultrasonic bath was used with recovery in the range of 94.8% to 104.3%. The limit of detection and limit of quantification values for R-amygdalin were 0.13 mg/L and 0.40 mg/L, respectively. The developed method proved to be precise with the intra-day and inter-day relative standard deviation values less than 2.23%.

Prevention of epimerization and quantitative determination of amygdalin in Armeniacae Semen with Schizandrae Fructus solution

Armeniacae Semen not only contains amygdalin, but emulsin also, which is an enzyme that hydrolyzes amygdalin. The extraction yield of amygdalin from Armeniacae Semen was low, due to the presence of emulsin, when extracted with water. When Schizandrae Fructus solution was used as the extractant; however, amygdalin was almost completely extracted, regardless of the cutting size, due to the absence of the influence of emulsin. In addition, when the crude powder or small piece forms were used with Schizandrae Fructus solution, on epimerization of the D-amygdalin into neoamygdalin occurred. D-amygdalin and its conversion product, neoamygdalin, were quantitatively analyzed by reverse-phase, high-performance liquid chromatography (HPLC), with an optimized eluent of 10 mM sodium phosphate buffer (pH 2.3), containing 11.5% acetonitrile. The concentration and detector response were linearly correlated over the range 0.05 to 2 mM. The detection limits for both D-amygdalin and neoamygdalin were approximately 5 microM for the amount injected.

Quantitative determination of amygdalin epimers from armeniacae semen by liquid chromatography

D-amygdalin and its conversion product, neoamygdalin, were quantitatively analyzed on reverse-phase, high-performance liquid chromatography with an optimized eluent of 10 mM sodium phosphate buffer (pH 3.1) containing 8.5% acetonitrile. Linearity between concentrations and detector responses was obtained in the range from 0.05 to 0.5 mM. The detection limits for D-amygdalin and neoamygdalin were approximately 5 microM per injected amount. Armeniacae semen contains not only amygdalin but also emlusin, which is an enzyme that hydrolyzes amygdalin. When extracting amygdalin from a whole piece of armeniacae semen in boiling water, there was almost no influence of emulsin; which increased the extraction efficiency. However, conversion of d-amygdalin into neoamygdalin at high temperature was found. In this report, we solved this problem by using 4% citric acid as an extractant. This solution also prevented the extraction process from being affected by emulsin. In addition, the extraction efficiency remained the same as that when methanol was used as an extractant, regardless of the cutting size.

Reverse-phase HPLC separation of D-amygdalin and neoamygdalin and optimum conditions for inhibition of racemization of amygdalin

In boiling aqueous solution, D-amygdalin usually begins to convert into neoamygdalin in 3 min and more than 30% of the initial D-amygdalin is found as neoamygdalin after 30 min. In this report, we establish methods for simple HPLC analysis and the inhibition of D-amygdalin conversion. D-Amygdalin and its conversion product, neoamygdalin, were clearly separated on reverse-phase column chromatography by an optimized eluent of 10 mM sodium phosphate buffer (pH 3.8) containing 6% acetonitrile. Linearity for analyzing D-amygdalin and neoamygdalin was observed in the range from 0.05 to 0.5 mM. The detection limits for D-amygdalin and neoamygdalin were ca. 5 microM per injected amount. We found that D-amygdalin conversion was completely inhibited by adding 0.05% citric acid to the aqueous solution before boiling. To prevent the loss of pharmaceutical potency of Tonin, we applied this method to measure the conversion rate of D-amygdalin. We confirmed that D-amygdalin conversion in Tonin is effectively inhibited by acidic boiling solution with 0.1% citric acid.