Lawsone quantification in Lawsonia inermis L. by HPLC-MS: How does the temperature and pluviometry affect lawsone concentration?

Lawsonia inermis L, commonly known as Henna belongs to the family Lythraceae. It is cultivated in tropical, subtropical and warm temperate areas in particular to North Africa and Asia. It's a plant with a wide spectrum of biological activities; it's widely used in Moroccan traditions especially for cosmetic purpose in all special occasions such as weddings, birth or circumcisions. This usage is related to its brown dark colour and the main compound responsible of this coloration is lawsone a naphtoquinone. Generally, the humidity and temperature as well as the nature of the soil influence the accumulation of secondary metabolites in a plant. In this work, it was demonstrated for the first time that a small change in temperature alone induces a large change in the concentration of lawsone in henna in geographically very close regions. This study aimed to evaluate the concentration of Lawsone in planted Henna (Lawsonia inermis L) from four different cities in the South Eastern Morocco, namely Tazzarine, Foum Zguid, Zaroga and Errachidia. Quantitative analysis by High Performance Liquid Chromatography-Electrosray Ionisation-Qtrap-Mass Spectrometry (HPLC-ESI-Qtrap-MS) showed that Foum Zguid is characterized by the highest level of Lawsone (0.6 %). Errachidia has the lowest amount of Lawsone. After statistical analysis, important correlation between temperature and lawsone concentration was demonstrated. In particular 2 locations showed a very high pourcentage of lawsone; Foum Zguid and Zagora that were more in the south. In the opposite, there was no significant correlation with the precipitation. Samples with humid climate and high pluviometry showed lower content of Lawsone. The analysis method was validated and principal component analysis on quantitative data was performed, correlation between, temperature, pluviometry and Lawsone content was established.