Herbal mixtures with claimed slimming activity: determination by TLC and HPLC of illegally added drugs.

A method for the detection and quantitation of several undeclared drugs in herbal preparations with slimming activity is proposed. Samples containing various anorexics, hypoglycemics and antidepressants were prepared by addition of the drugs to a synthetic mixture containing the most commonly used plant powders for those preparations. Each sample was subjected to a treatment that permitted, after a simple ethanolic extraction, the identification of the drugs by TLC using three different solvent systems. A further purification of the ethanolic solution through a polyamide column allowed for quantitative analysis of the drugs by a RP-HPLC method. The analytical recovery was good (88-97%); the calibration curves were linear over a wide range of drug concentrations (30-500 micrograms/ml) (r > 0.9995); the precision was high (CV% = 0.4-2.8) as well as the accuracy (96-102%).