HPTLC fingerprint method for the detection of sennosides in Senna dry extracts

In 2015 a new HPTLC method was proposed as part of the revision of the herbal drug monographs in the European Pharmacopeia Ph.Eur. of senna leafs and pods [1]. However, the proposed method was unspecific for the active constituents and showed difficulties with the repeatability in several laboratories. Therefore, alternative methods for fingerprinting were tested. The focus has been based on a fingerprint showing the active compounds which are mainly sennoside A and B and this in a fast and simple method.

The mobile phase used for senna folium in the pharmacopoeia of the people's republic of China in combination with potassium hydroxide reagent showed the best result in the separation and characteristic visualization of the sennosides. The sennosides show u-shaped zones which broaden with increasing application amount. The addition of acid to the mobile phase was tested but showed no improvement. The zones are under control by the applied amount. The sennosides A and D (zones [d]) are suitable as system suitability test for the method. However, sennosides D is not easily obtainable as reference substance; therefore, a senna dry extract CRS was used as cost-effective alternative. The chromatograms of senna leafs and fruits are comparable to the ones of the senna dry extracts shown.

Fig. 1: Chromatograms of different senna dry extracts
SST: Senna extract CRS, R: sennoside A and B, R1/4: sennoside A and B diluted to 1/4, E1 – 7: different batches ethanolic fructus dry extract, E8/9: methanolic folia dry extracts, E10 – 12: aqueous fructus dry extracts

[1] EDQM. Draft for the revision of the monographs Senna leaf (0206), Senna pods, Alexandrian (0207) and Tinnevelly (0208) – PA/PH/Exp. 13A/T (15) 19 – 21 ANP. Pharmeuropa 27.3, 169 – 186 (2015).