Antimicrobial activity of Lawsonia inermis L.

Henna (Lawsonia inermis L.) is a small shrub frequently cultivated in India, Persia, and along the African coast of the Mediterranean Sea. Powdered leaves of this plant, in the form of a paste, are used both as a cosmetic and as a remedy for boils, wounds, and some mycotic infections in certain countries of the Middle East. The antibacterial activity of an aqueous extract of henna leaf and some properties of this extract are given in this paper. The following bacteria were used: Bacillus cereus, B. anthracis, Escherichia coli, Proteus vulgaris, Staphylococcus aureus, Erwinia carotovora, Agrobacterium tumefaciens, and Xanthomonas campestris. Cultures of X. canpestris and A. tumefaciens were obtained from the American Type Culture Collection. All others were from the Microbiology Department, Tehran University. A 10-ml amount of each bacterial suspension was prepared from the stock culture, and the turbidity was adjusted to give 65% light transmission at 650 mu. This dilution resulted in approximately 150 million bacteria per ml. The henna extract was prepared by adding 1 g of powdered dried leaves to 10 ml of sterile distilled water. After being shaken, the preparation was allowed to stand for 4 hr. It was filtered through cheesecloth, then through filter paper, and finally through a Sietz filter into a sterile 100-ml filter flask. Portions of the filtrate were autoclaved at 14 psi for 15 min. Test plates were prepared by adding 0.2 ml of the bacterial suspension to a test tube containing 10 ml of melted nutrient agar at 50 C and pouring into the petri plate. After solidification, a 14-mm core of agar was removed from the center of each plate with a sterile cork borer, and 0.5 ml of henna extract was placed in each hole. There were six replicates for each treatment. Daily observations were made, and the zones of inhibition were measured in millimeters when a uniform growth of bacteria covered the agar surface. Both gram-positive and gram-negative bacteria were inhibited. Inhibitory action was greatest against B. anthracis and least against S. aureus. No bacterial colonies were observed within the zone of inhibition in plates of B. anthracis and X. campestris when the plates were incubated at room temperature (23 C) for 8 to 10 days (Table 1). In determining the activity of raw and autoclaved extract against B. anthracis, 0.2 ml of the bacterial suspension with an optical density of 0.20 was added to two test tubes, each containing 9 ml of nutrient broth. The suspension was carefully shaken to insure an even distribution of the culture. Then 1 ml of the raw or autoclaved extract was added to the two tubes, and tubes were again shaken. The antimicrobial activity of the extract against B. anthracis was increased by heat (Fig. 1). This is probably the reason that