Abstract
This study aimed to assess the analgesic and anti-inflammatory effects of lawsone isolated from henna leaves (Lawsonia inermis). 
 Methods: A total of 120 healthy adult mice (weighing about 25±5 g) were included in this study. Sixty mice out of the total were used to determine LD50, 30 mice to determine the anti-inflammatory test, and the remaining (30 mice) were used for an analgesic test. The hot plate was used to determine the analgesic effect, while the anti-inflammatory effect was determined by the ability of the compound to minimize the inflammation and edema caused by the injection of carrageenan. 
 Results: Lawsone was isolated from Lawsonia inermis. A Stuart SMP10 digital melting point apparatus was used for measuring all melting points. Infrared spectrometer FT-IR 400D was used for measuring/recording IR spectra (KBr) which the frequency of absorption was represented as cm−1. For 1H-NMR spectrum recording, a Bruk-spectrophotometer of 400 MHz was used with internal TMS standard, with deuterated Ś 2.51 ppm for acetone-d6, remained solvent signals as well as 13C.NMR was used. TLC was utilized as adsorbent, UV light, or iodine-completed visualization to verify compounds' purities.
 The LD50 of the oral lawsone was 96 mg/kg, and the highest dosage that did not kill any of the experimental animals was 80 mg/kg, which was used to investigate lawsone's analgesic and anti-inflammatory effects.
 Lawsone and aspirin possessed an analgesic effect compared to the control group (p<0.0001 and p<0.001, respectively); however, lawsone induced a potent analgesic effect compared to aspirin (p<0.1). In contrast, Lawsone and aspirin exerted an anti-inflammatory effect (p<0.05) compared to the control group and were equipotent in carrageenan-induced hind paw edema.
 Conclusion: It is concluded that lawsone possesses analgesic and anti-inflammatory effects, which endorse the practical medical importance of Lawsonia inermis. The latter is widely used traditionally for these purposes own to its cost-effectiveness and safety; however, further studies are required to determine the systemic safety of lawsone
Highlights
Lawsonia inermis Linn (Family: Lythraceae) is a plant often known as henna, predominant in tropical and subtropical regions and has been extensively investigated and used worldwide in traditional medicine and as cosmetic
Lawsone induced potent analgesic effect compared with aspirin as determine by the time of analgesic period recorded in hot plate model (p
Our study revealed that the lawsone content in henna leaves was 1.2 %, slightly higher than some researchers indicated [35, 40]
Summary
Lawsonia inermis Linn (Family: Lythraceae) is a plant often known as henna, predominant in tropical and subtropical regions and has been extensively investigated and used worldwide in traditional medicine and as cosmetic. It has been used as a dye for over 9000 years for its cosmetic value. Henna is distributed in Egypt, Africa, Ethiopia, Sudan, Somalia, Niger, Zaire, Burkina Faso, Benin, Gambia, Cote D'Ivoire, Ghana, Togo, South Africa, Guinea-Bissau, Guinea, Sierra Leone, Mali, Senegal, Liberia, Comoros, Nigeria, Seychelles as well as in Asia (Pakistan, Sri Lanka, India). Henna is commonly grown in tropical areas, including North and East Africa, the Arabian Peninsula, the Middle East's southern regions, and South Asia [2, 3]
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