Bactericidal activity of Myrrh extracts and two dosage forms against standard bacterial strains and multidrug-resistant clinical isolates with GC/MS profiling

Myrrh is the resinous exudate obtained by the incision in Commiphora molmol trees (Family Burseraceae). The bactericidal activity of its hexane extract was compared to its essential oil (MEO) using viable count technique against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (Ps. aeruginosa). MEO exhibited a better activity with > 99.999% killing of both tested strains after 2 h contact time. MEO was tested using the same technique against four multidrug resistant isolates: S. aureus (MRSA, sputum), Escherichia coli (E. coli, urine), Ps. aeruginosa (wound) and Klebsiella pneumonia (K. pneumonia, sputum). Highest bactericidal activity was observed against Ps. aeruginosa while lowest was against K. pneumonia (99.59 and 54.04% killing, respectively after 2 h contact time). A cream and mouthwash were formulated using 5% v/v MEO. The cream showed a better activity against Ps. aeruginosa than S. aureus (95.11 and 86.76% killing, respectively after 2 h contact time). The in vitro treatment of ca 10(7) CFU/ml S. aureus cells suspended in 10% saliva with the mouthwash produced ca 46% killing within the first 15 min reaching ca 99.999% after 30 min. Cytotoxic studies of both the essential oil and hexane extract on human liver cancer (Hep G2), human breast cancer (MCF-7) and colon cancer cell lines (HCT-116) revealed a promising in vitro activity. Highest activity was recorded for the essential oil on MCF-7 with IC(50) 10.93 ± 0.32 μg/ml. GC/MS analysis allowed the identification of 17 and 9 compounds representing 92.01 and 99.99% of the hexane extract and essential oil, respectively. Furano-eudesma-1,3-diene (15.99%) and 2-acetoxy-furano-diene (26.82%) were the major identified compounds in the hexane extract and essential oil, respectively. These results indicate that Myrrh essential oil is a promising antibacterial and cytotoxic agent that can be formulated in suitable dosage forms.