26 0009-3130/18/5401-0026  2018 Springer Science+Business Media, LLC Chemistry of Natural Compounds, Vol. 54, No. 1, January, 2018 LAWSONOL, A NEW BIOACTIVE NAPHTHOQUINONE DIMER FROM THE LEAVES OF Lawsonia alba Shammi Akhter, 1,2 Satyajit Roy Rony, 1 Muhammad Abdullah Al-Mansur, 3 Choudhury Mahmood Hasan, 4 Khondaker Miraz Rahman, 5* and Md. Hossain Sohrab 1* A new bioactive naphthoquinone dimer, lawsonol[2-(1,4-dioxo-1,4-dihydronaphthalen-2-yloxy)-3- hydroxynaphthalene-1,4-dione] (1), was isolated from the leaves of Lawsonia alba. Its structure was established on the basis of spectral data, including 2D NMR and HR-MS. Compound 1 exhibited in vitro antibacterial activity against Bacillus megaterium, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Keywords: Lawsonia alba, Lythraceae, lawsonol, antibacterial activity. Medicinal plants are ideal targets for the discovery of potential bioactive compounds or lead structures for new drug development 1. Lawsonia is a monotypic genus represented by Lawsonia alba (synonym Lawsonia inermis L.) 2. The plant belongs to the Family Lythreaceae and is native to Southwest Asia and North Africa; it is cultivated in many districts of Bangladesh 3. It contains a wide range of phytochemicals, including lawsone, isoplumbagin lawsoniaside, lalioside, lawsoniaside B, syringinoside, daphneside, daphnorin, agrimonolide-6-O--D-glucopyranoside, (+)-syringaresinol-O--D- glucopyranoside, (+)-pinoresinol di-O--D-glucopyranoside, isoscutellarin-3, hennadiol, (20S)-3-30-dihydroxylupane, lawnermis acid, 3-methylnonacosan-1-ol, laxanthones I, II, III, lacoumarin, etc. 4–10. The key coloring agent present in leaves is lawsone 8.The various in vitro and in vivo studies of L. alba reported that the plant possesses antifungal, antiparasitic, antiviral, anticancer, antidiabetic, tuberculostatic, anti-inflammatory, antifertility, and wound healing properties 2. Traditionally, a paste of leaves is used to prevent skin inflammation, as well as to cure ulcers and wounds. The leaves have also been used to treat constipation and as a hematinic and febrifuge, and to treat cough, burning sensation, hemicranias, cephalagia, diarrhea, dysentery, leucoderma, leprosy, boils, scabies, hepatopathy, anemia, hemoptysis, ophthalmia, etc. 2. Compound 1 (Fig. 1) was obtained as light orange crystals. Accurate mass measurements of 1 obtained by FT-ESI-MS yielded a parent mass at m/z 345.0408 in the negative ionization mode (calcd mass 345.0405), corresponding to the [M – H] – of a compound with a molecular formula of C 20 H 10 O 6 , accounting for 16 degrees of unsaturation. The 13 C NMR spectrum (Table 1) displayed 20 carbon resonances, while the HSQC experiment indicated that nine out of the 20 carbons were attached to protons. The 1 H NMR (Table 1) and DEPT 135 spectra revealed the presence of nine aromatic/olefinic methines.The one four-proton doublet at  8.05 ppm and two two-proton triplets at  7.74 and 7.67 ppm indicated the presence of two disubstituted aromatic rings. The coupling pattern suggested that 1 is likely a dimer. 1) Pharmaceutical Sciences Research Division, BCSIR Laboratories Dhaka, Dr. Qudrat-I-Khuda Road, Dhanmondi, Dhaka-1205, Bangladesh, e-mail: psrd_bcsir@yahoo.com; 2) Department of Pharmacy, University of Asia Pacific, 74/A, Green Road, Dhaka-1215, Bangladesh; 3) Institute of National Analytical Research and Service, BCSIR Laboratories Dhaka, Dr. Qudrat-I-Khuda Road, Dhanmondi, Dhaka-1205, Bangladesh; 4) Manarat International University, Plot No. CEN-16, Road No. 106, Gulshan-2, Dhaka, Bangladesh; 5) Kings College London, Institute of Pharmaceutical Science, Britannia House, 7 Trinity Street, London, SE1 1DB, UK, e-mail: k.miraz.rahman@kcl.ac.uk. Published in Khimiya Prirodnykh Soedinenii, No. 1, January–February, 2018, pp. 26–28. Original article submitted August 26, 2016. DOI 10.1007/s10600-018-2251-0