Chemical fingerprinting of Lawsonia inermis L. using HPLC, HPTLC and densitometry.

INTRODUCTION: Lawsonia inermis L. is a natural red colouring agent, commonly named "Henna", which is used to dye skin and hair. The aim of this study was to evaluate the quality of L. inermis that is commercially available as a raw plant material or preparation in order to guarantee good quality products.

OBJECTIVE: To develop a simple protocol for the qualification of different samples labelled as L. inermis by using the HPTLC densitometry method and to identify possible adulterations with other plants.

METHODOLOGY: Samples of leaves of L. inermis were extracted with methanol. Two chromatographic methods were developed to determine the chemical fingerprinting of L. inermis. The first was based on HPTLC identification followed by densitometric measurements at 337 nm. The second was based on RP-HPLC separation with gradient elution and photodiode array detection at 337 nm. Samples of Cassia obovata Collad., and Indigofera tinctoria L., were treated in the same way.

RESULTS: The simplicity of the sample preparation, and the possibility of analysing several samples of herbal products simultaneously in a short time, make HPTLC the method of choice. The HPTLC method was feasible for the comprehensive quality evaluation of herbal products. From the comparison of their "fingerprint", it was possible to detect substitution of plants that are different from those declared on the label.

CONCLUSION: The HPTLC may be used as a rapid method by which to control the quality of raw plant materials and formulations based on the title plant.