THE ANALYSIS AND STANDARDISATION OF ANTHRAQUINONE DRUGS¹

Introduction

The object of analysing and standardising Crude Drugs and their Preparations is to produce a figure which will be directly related to therapeutic activity. To achieve this object it is necessary, (a) to know precisely which chemicals present are the active ones, (b) to be certain that the final analytical figure obtained represents these chemicals quantitatively and exclusively; and (c) that the analytical process is sufficiently defined so that all workers using it will get the same figure for the same sample. With anthraquinone drugs it is particularly difficult to satisfy these conditions. The active principles are anthracene derivatives but we have shown that the form in which they occur is most important. Primary glycosides are more active than secondary ones; the aglycones are less active than both, and the oxidised form of the aglycone is less active than the reduced form. At the Conference in Miinster in 1959 I described the biological and chemical evidence for these conclusions (Fairbairn 1959).

The analytical problems involved in separating these closely similar compounds are considerable. The process is therefore complicated and, since the final analytical step usually involves colorimetry, the presence of small amounts of impurities can greatly effect the results. In England, we have had a joint Committee of the Pharmaceutical Society and the Society for Analytical Chemistry working for several years on this problem but so far we have got no further than work on Senna.