Procyanidin content of Hawthorn berries sourced from either Crataegus monogyna Jacq. (Lindm.) or C. laevigata (Poir.) DC. is defined in the European Pharmacopoeia monograph[1]. Procyanidin content is determined by the HCl-butanol spectrophotometric method which has a long history of use. More recent work has shown that this method tends to underestimate the procyanidin content and can be improved by the addition of acetone to the solubilisation step [2]. More detailed data can also be obtained using thiolysis and subsequent HPLC-MS analysis [3].
Comparing a suite of commercial berry (6) and leaf (4) C. monogyna samples analysed by the BP method and the modified acetone-HCl-butanol method confirmed that the former underestimated procyanidin content by at least one order of magnitude. Leaf samples by the BP method ranged from 0.25-0.30% whilst the same samples gave 4.1-6.8% by the acetone-HCl-butanol modified method. Similarly, the procyandin content of berry samples was in the range 0.035-0.23% by the BP/EP method but much higher by the modified acetone-HCl-butanol method (0.8-2.1%).
Results on the same suite of samples by the thiolysis-HPLC-MS method were consistent across the leaf samples (3.6-4.5% procyanidin), but significantly and consistently lower for the berry samples (0.2-1.5%). Thiolysis-HPLC-MS analysis also provides more detailed chemical information on the mean degree of polymerisation, procyanidin:prodelphinidin ratio, cis:trans flavan-3-ol ratio as well as information on various aspects of A-type procyanidins present.
We conclude that the current EP method greatly underestimate the concentration of procyanidins in Crataegus and suggest the method be revised.
[1]. Ph. Eur. monograph 1220
[2]. Grabber, J.H., Zellert, W.E., Mueller-Harvey, I. J. Agric. Food Chem., 61, (2013), 2669-2678
[3]. Ropiak, H.M., Ramsay, A. and Mueller-Harvey, I. J. Pharm. Biomed. Anal., 121, (2016) 225-231.