Green Biotechnology for Aqueous Citric-Acid Extraction of Lawsone from Henna Leaves

Henna leaves have been used as a natural hair dye due to the presence of lawsone, a red-orange naphthoquinone pigment.In this work, we investigate three extraction techniques: conventional solvent reflux extraction, Soxhlet extraction, and ultrasonic-assisted extraction (UAE) to isolate lawsone from henna leaf powder using water (with mild acid addition) as a green solvent.The effects of extraction temperature (25-70 °C), duration (2-9 h), and solution acidity (citric acid, up to 0.01 M) on lawsone yield were examined.UV-Vis spectroscopy was used to quantify lawsone content in the extracts.Optimal extraction conditions were identified at a moderate temperature of 50 °C, an extraction time of 5 h, and citric acid pH 3.2.Under these conditions, ultrasonic extraction achieved the highest lawsone yield, followed closely by heated solvent extraction, whereas Soxhlet extraction at 100 °C yielded comparatively less lawsone.The lawsone-rich extracts showed a characteristic absorbance peak around 350 confirming the target compound's presence.This study demonstrates that ultrasonic-assisted, mildly acidic aqueous extraction is an effective and eco-friendly approach to obtain lawsone from henna leaves, outperforming traditional methods in both yield and preservation of the active dye.These findings can facilitate the sustainable production of natural henna-based hair dyes and other cosmetic applications.