In continuation of our studies with chemoprevention potential of plant-derived naphthoquinone derivatives, leaf powder of the
medicinal plant Lawsonia inermis L, commonly known as ‘henna’, was evaluated by its inhibition of the Epstein-Barr virus early antigen
(EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Lawsone (2-hydroxy-
1,4-naphthoquinone), the reddish orange pigment artifact formed during the extraction or preparation of the dye from henna leaves and
believed to be the active component, was also assessed in this in vitro assay. Both showed a profound inhibition (>88%) of EBV-EA
activation. In the in vivo two-stage mouse skin carcinogenesis study using UV-B radiation for initiation and TPA for tumor promotion,
oral feeding of henna (0.0025%) in drinking water ad libitum decreased tumor incidence by 66% and multiplicity by 40% when
compared to the positive control at 10 weeks of treatment. Similarly, in the above mouse model, orally fed lawsone (0.0025%) decreased
tumor incidence by 72% and multiplicity by 50%. The tumor inhibitory trend continued throughout the 20-week test period. Similar
antitumor activities were observed when henna (0.5 mg/ml) was applied topically on the back skin in the UV-B initiated, TPA promoted
and peroxynitrite initiated, TPA promoted mouse skin carcinogenesis models. Topically applied lawsone (0.015 mg/ml) also exhibited
similar protection against tumor formation in the 7,12-dimtehylbenz(a)anthracene induced and TPA promoted skin cancer in mice. Also,
there was a delay of 1 to 2 weeks in tumor appearance in both henna and lawsone treated groups compared to control in all three test
models. This study ascertains the skin cancer chemopreventive activity of henna leaf powder and lawsone when administered by either
oral (through drinking water) or topical (by application on the back skin) routes. Further, it emphasizes the need for the evaluation of
these henna-derived green chemopreventive candidates in combination with currently used sunscreen agents for complementary
anticancer potential against UV-induced skin carcinogenesis.
Chemoprevention, epstein-Barr virus antigen assay, henna leaf powder, lawsone, mouse skin cancer models.
College of Pharmacy, Howard University, 2300 4th Street, NW, Washington, DC 20059, USA.