Determination of the Total Alkaloid Content of Thermopsis Dry Extract by HPTLC-Densitometry

Abstract

When used to quantify alkaloids in thermopsis dry extract, acidimetric titration has several limitations, including insufficient specificity of the method and arbitrary selection of a titration endpoint. Different parts of the Thermopsis lanceolata plant produce alkaloids in different proportions: the herb is rich in thermopsine, whereas the seeds are rich in cytisine. Since thermopsine and cytisine have different pharmacological effects, it is important to identify and quantify individual alkaloids in thermopsis dry extract.The aim of the study was to develop and validate an analytical procedure for identifying and quantifying total alkaloids in thermopsis dry extract by high-performance thin-layer chromatography (HPTLC) with densitometric detection.Materials and methods. The study included samples from two pilot-scale batches of thermopsis dry extract and reference standards for cytisine and thermopsine. The authors used Merck HPTLС Silica Gel 60 F254 20×10 cm plates for chromato-graphic separation and analysed the results with a CAMAG® TLC Scanner 4 densitometer and the winCATS software.Results. The authors identified thermopsis dry extract using HPTLC separation followed by spectrodensitometry. The alkaloid-specific solution applied to chromatography plates helped to identify the three most abundant and four minor alkaloids of thermopsis. The most abundant alkaloids were thermopsine, cytisine, and an unidentified alkaloid with a retention factor of approximately 0.2. These three alkaloids accounted for almost 80% of the total alkaloid content of the dry extract. The authors quantified cytisine, thermopsine, and total alkaloids expressed as thermopsine.Conclusions. The authors developed and validated an analytical procedure for identifying and quantifying total alkaloids in thermopsis dry extract. This procedure offers the possibility of reducing the analysis time from 4–5 hours to 2–2.5 hours.

Keywords

• hptlc-densitometry
• thermopsis dry extract
• cytisine
• thermopsine
• alkaloids