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.