Specific HPLC determination of toxic alkaloids in aconite roots compared with amount ot total alkaloids determined by titration

Abstract

Aconite roots are known to be very toxic due to diterpene ester alkaloids [1]. Therefore, in Chinese medicine they are only used after processing. Hydrolysis of the ester groups decreases toxicity [2]. Nevertheless, several cases of poisoning by unprocessed or improperly processed aconite roots have been reported [3]. Recently we suggested a specific sample preparation method and HPLC assay for the analysis of toxic aconite alkaloids [4]. Now, an improved method with an even better resolution is presented. Using this method, we have determined the content of mesaconitine, aconitine and hypaconitine in 30 commercial samples of processed aconite roots. In most of the samples, toxic aconite alkaloids were not detectable, or only traces were found. However, in four samples we could detect more than 0.04% of hypaconitine and mesaconitine, the highest with a content of 0.16%. Therefore, this method is suggested as a purity test for the European Pharmacopoeia. Acute toxicity of batches high in hypaconitine and mesaconitine was also confirmed in CFLP mice. In the aconite monograph of the German Homeopathic Pharmacopoeia, alkaloids are determined by a titration method. We compared the results of HPLC analysis of toxic alkaloids (mesaconitine, aconitine and hypaconitine) with the results obtained by the titration method, and found no correlation. Samples which were lacking mesaconitine, aconitine and hypaconitine, still contained up to 0.2% alkaloids determined by titration. Therefore, titration of alkaloids is not appropriate as an assay for toxic alkaloids in aconite roots.