Most of the beneficial biological effects (e.g. neurosedative, antioxidant, and antimicrobial) of black horehound (
L.) are because of its phenylpropanoid glycoside content. A rapid TLC-densitometric method with acceptable accuracy has been established for quantitative analysis of the most characteristic components of black horehound. Experiments were performed to establish the optimum conditions for densitometric measurement and for storage of extracts. Practical application of the elaborated method is reported for five plant extracts.