Über den Mechanismus der asymmetrischen katalytischen Racemisation des Amygdalins

Smith, Isobel Agnes

doi:10.1002/cber.19340670735

Cited by 2 publications

(1 citation statement)

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“…The Cyclobond I 2000 RSP with a 20:80 v/v methanol/water mobile phase was used for all kinetic studies on amygdalin epimerization. Two early, very detailed, epimerization studies, which are more than four decades old, exist in the German literature. , The authors examined some of the factors influencing amygdalin epimerization such as (i) solvent, water, methanol, ethanol, ethyl acetate, and an azeotrope of methanol/ethyl acetate; (ii) temperature; and (iii) pH. The mandelonitrile stereogenic center changes configuration as indicated (Figure ): …”

Section: Resultsmentioning

confidence: 99%

Problems and Pitfalls in the Analysis of Amygdalin and Its Epimer

Wahab

Breitbach

Armstrong

et al. 2015

J. Agric. Food Chem.

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α-[(6-O-β-d-Glucopyranosyl-β-d-glucopyranosyl)oxy]-(αR)-benzeneacetonitrile, or R-amygdalin, is the most common cyanogenic glycoside found in seeds and kernels of the Rosaceae family and other plant genera such as Passiflora. Many commercially important seeds are analyzed for amygdalin content. In "alternative medicine", amygdalin has been sold as a treatment for cancer for several decades without any rigorous scientific support for its efficacy. We have found that there are some inconsistencies and possible problems in the published analytical chemistry of amygdalin. It is shown that some analytical approaches do not account for the presence of the S-isomer; therefore, a fast reliable method was developed using a chiral stationary phase and HPLC. This approach allows "real-time" monitoring and complete and highly efficient separations. It is found that the S-amygdalin continuously forms in aqueous solutions. A striking result is that the conversion of amygdalin is glassware dependent. "Clean" vials from various vendors can show drastically different reaction rates of the conversion to the isomer (S-amygdalin, also called neo-amygdalin). The epimerization kinetics are dependent on the solvent, temperature, pH, and the nature of the container. For example, epimerization in water was complete in <15 min in a new glass vial taken from the box, whereas it can take >1 h in specially cleaned glassware. Conversely, epimerization can be significantly delayed at high temperature if high-density polyethylene is used as the container. Hence, inert plastic containers are recommended for storage of aqueous amygdalin solutions. Commercial preparations of R-amygdalin actually contain greater quantities of S-amygdalin and ∼ 5% of other degradation products.

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