Chemical analysis by GC-MS and in vitro antibacterial activity of Alkanna tinctoria extracts against skin infection causing bacteria

Alkanna is a traditional medicinal plant; Bedouin of Saudi Arabia use the roots of the plant for the treatment of many skin diseases. Water and ethanol extracts of Alkanna roots were evaluated for their antibacterial activity against four pathogenic bacteria responsible for skin infections i.e. Pseudomonas areuginosa ATCC 27853, Bacillus subtilis (clinical strain), Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25928. The agar well diffusion method was employed for the antibacterial screening of crude extracts. Ethanol extract inhibited the growth of all bacteria, as depicted by the zone of inhibition of bacteria around the well filled with extract. The maximum zone of inhibition was observed against B. subtilis (28.0 mm) followed by S. aureus (24.7 mm), P. areuginosa (18.7 mm) and E. coli (15.3 mm). The water extract showed minor antibacterial activity against B. subtilis and S. aureus however, it was found ineffective against other two pathogens. The streak method was used to determine the Minimum Inhibitory Concentration (MIC). The MIC value of ethanol extract against B. subtilis and S. aureus was 2 μl/ml, whereas, against E. coli and P. areuginosa it was 4 μl/ml. The qualitative analysis of the ethanol extract was conducted by the GC-MS. The major compounds detected in the ethanolic extract of Alkanna were akanin, acetyl-alkanin, ethane, 1, 1-dichloro-, 1H-enzotriazole, 4-nitro, 2- chloroethyl (methylsulfonyl) methanesulfonate and 2, 5-cyclohexadien-1-one, 4-diazo-. Besides that several other napthoqinones and esters were detected in the extract. Results of present study manifest that extract of Alkanna has the potential to inhibit the growth of pathogens responsible for skin infections