Antimicrobial properties of Lawsonia inermis : a review

Australian Journal of Medical Herbalism, Fall, 2007 by O.A. Habbal, A.A. Al-Jabri, A.G. El-Hag

The antibacterial activity of the natural naphthoquinone products alkannin and shikonin and their derivatives has been investigated (Riffel 2002). In general they are active against gram positive bacteria such as Staphylococcus aureus, Enterococcus faecium and Bacillus subtilis, but are inactive against gram negative bacteria (Papageorgiou 1999). In nosocomial infection, Staphylococcus aureus is one of the most prevalent microorganisms worldwide. Methicillin resistant strains represent 15-45% of all Staphylococcus aureus isolates (Emori 1993). This may explain the arduous search for new antimicrobial agents as an important line of research.

For the naphthoquinones to have such antimicrobial activity, active compounds must possess at least a substitution at position 2 (as is the case in lawsone Fig 1) or 3, which is either an electron releasing or weaker electron withdrawing group (Greshon 1975). This structure activity relationship is reinforced further with studies that indicated the antimicrobial activity of a family of isoxazolylnaphthoquinones requires a free keto group at position 1, and the substituent at position 2 must be a hydroxyl group (Bogdanov 1993). Such compounds were found to protect mice infected with Staphylococcus aureus, inhibiting septicaemia in vivo (Albesa 1995).

Inhibitory action of henna was shown against both gram negative and gram positive microbes. In one report the inhibitory action was greatest against B. anthracis as it stood out from other tested bacteria (Malekzadeh 1968). Lawsone, the antimicrobial agent in henna (Malekzadeh 1968, Sharma 1995) is highly soluble in water, partially soluble in 70% ethyl alcohol and heat stable. Chromatography studies demonstrated the presence of phenolic compounds in the substance (Malekzadeh 1968). Such compounds exerted inhibitory effects upon common nosocomial urinary tract pathogens such as Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeroginosa and Staphylococcus aureus at certain concentrations (Bhuvaneswari 2002).

Decoction of henna leaves has been used as a gargle in sore throats (Chopra 1958). Crude and ethonolic extract of Lawsonia inermis leaves showed dose dependent analgesic, antipyretic and anti-inflammatory effect in rats (Ali 1995). The effects of water and chloroform extracts of the leaves of henna plant against the primary invaders of burnt wounds was also investigated (Muhammad 2005). Inhibition of the growth of such microorganisms suggests that henna may be valuable in the management of burnt wound infections (Muhammad 2005).

In our own laboratory we have undergone investigations on crude extracts of fresh and dry local (Omani) henna leaves and seeds against 3 standard bacterial strains, Staphylococcus aureus, Escherichia coli and Pseudomonas aerugenosa, and eleven different bacterial strains obtained from patients attending hospital clinics. We found, as shown above, that all fresh and dry henna leaves and seeds possessed antibacterial activity against all microorganisms tested in vitro (Habbal 2005).