New insights into the chemical composition and biological activities of Lawsonia inermis seeds and leaves: a comparative study

Lawsonia inermis (henna) is a cosmetic popular plant and is used to dye hair, as well as decorate the skin. Nevertheless, this plant has also a great number of bioactive compounds that have great therapeutic potential. In this study, a comparative investigation of the chemical composition and biological activities of seeds and leaves of L. inermis collected from southern Morocco was conducted in order to explore their valorization potential. The chemical analysis fatty acids of henna seed oil showed a composition of 56.3% linoleic acid, 21.4% palmitic acid and 10.6% oleic acid. The unsaponifiable portion revealed a predominance of β-sitosterol (61.24%), while the tocopherol profile was dominated by γ-tocopherol (123.4 mg/100g), making it an excellent nutricosmetic product due to the composition of nutrients found in henna seed oil. The antioxidant activity of the leaf extracts was also noteworthy with IC50 values of 9.1 µg/mL and IC50 of 80.1 µg/mL being obtained in the case of DPPH and ABTS respectively although the seeds registered a little lower value, indicating the abundance of phenolic compounds. In addition, seed and leaf extracts had good antimicrobial activities with minimum inhibitory concentrations (MIC) that fell below 10 mg/mL against bacterial strains including Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae. Correlation analysis suggested a strong relationship between phenolic content and antioxidant activity, although this analysis was conducted on a limited dataset. These results indicate that Moroccan L. inermis seeds and leaves have high concentrations of bioactive compounds. They also highlight the potential of henna seeds as a novel source of bioactive ingredients for cosmetics or pharmacy products and have a good potential of natural therapeutic and cosmetic use.