Optimization of aqueous extraction of henna leaves (Lawsonia inermis L.) and evaluation of biological activity by HPLC-based profiling and molecular docking techniques

Abstract

Due to the antimicrobial capabilities of henna leaf extract (Lawsonia inermis L.), this study intends to identify environmentally friendly ideal conditions for extracting bioactive compounds from henna leaf powder. For this purpose, the maceration method with a 100% aqueous solvent was selected for further analysis. Optimization of the extraction method was carried out by central composite design (CCD) protocol as a subset of Response Surface Methodology (RSM). The temperature of 40–90 °C, extraction time of 2–24 h, and the solvent-plant weight ratio ranging from 10 to 100 mL/mg were all considered independent variables. Also, the amount of lawsone, as an active component, and the total phenolic content were tracked as responses. Finally, a yield of 30.59% was achieved under the best extraction condition at 40 °C, 2 h, and a solvent-plant weight ratio of 1:100. The biological activity of an aqueous extract was evaluated using an HPLC-based activity profiling and TLC bioautography method. Peaks collected as fractions between 3 and 30 min were tested for antibacterial activity against Staphylococcus aureus ATCC 25923, and micro fractions from 5, 6, 7.5, 9, 10.5, 12, 13.5, 15, 19, and 30 min exhibited significant inhibitory effects. All spotted fractions on the TLC plate inhibited the growth of Escherichia coli ATCC 25922, except for micro fractions from 3, 18, and 21 min. Moreover, molecular docking analysis of quinones in the extract identified 3a, 4a-Dihydroxy-a-tetralone (C-2) as the most potent compound in interacting with bacteria sterol 14-demethylase protein, with docking scores of − 6.715 and − 7.196 kcal/mol, respectively.