Isolation and characterization of 2-hydroxy-1,4-naphthoquinone (lawsone) from the powdered leaves of henna plant marketed in Ahwaz city of Iran

Regarding the therapeutic effects and traditional applications of henna, it was tried to isolate and purify Lawsone from the leaves of henna marketed in Ahwaz city of Iran by various methods of maceration and Soxhlet extraction techniques in different polar and non-polar solvents. Maceration of the powdered leaves in hot water with stirring for around 6 hours was carried out followed by addition of solid NaHCO3.The suspension was filtered by gravity. The filtrates were combined and acidified to pH 3 by addition of 0.12 M HCl. The filtrate was extracted with diethyl ether. The combined ethereal phases were washed with water and dried over anhydrous MgSO4. After the removal of ether on a rotary evaporator, a reddish solid material was obtained as crude product. The progress of the isolation of Lawsone was monitored by IR spectroscopy and TLC on silica gel. Column chromatography on silica gel 60 with a mixture of EtOH:EtOAc (1:2 v/v) as the mobile phase resulted in the formation of different colour zones. The crude product (0.5 g) was dissolved in 10 mL of the eluent and placed at the top of the column and the elution was started. Fractions of 10 mL were taken. Almost 50 fractions were collected. The compositions of all fractions were monitored by TLC. Fractions 25 -40 had the same Rf and contained Lawsone. The yield was very low (around 30 mg) (m.p. 191-194 °C).