Antibacterial and Anticancer Properties of Boswellia carteri Birdw. and Commiphora molmol Engl. Oleo-Resin Solvent Extractions

Abstract

Background: Boswellia carteri Birdw. (frankincense) and Commiphora molmol Engl. (myrrh) oleo-resins have traditionally been used for the growth inhibition of bacteria associated with skin diseases, urinary tract infections, respiratory infections, wound healing, dental disease and gastrointestinal disorders. Despite this, many bacterial pathogens are yet to be screened for susceptibility to frankincense and myrrh extracts. This study was undertaken to test extracts prepared from frankincense and myrrholeo-resins for the ability to inhibit microbial and cancer cell growth. Materials and Methods: Frankincense and myrrhresins were extracted and tested for antimicrobial activity using modified disc diffusion and MIC methods. Inhibitory activity against CaCo2 and HeLa cancer cell lines was evaluated using colorimetric cell proliferation assays. Toxicity was evaluated using an Artemia franciscana nauplii bioassay. The most promising inhibitory extracts were investigated using non-targeted GC-MS head space analysis (with screening against a compound database) for the identification and characterisation of individual components in the crude plant extracts. Results: The frankincense and myrrh extracts displayed broad spectrum antibacterial activity, inhibiting the growth of all of the bacteria screened against. The frankincense extracts were generally more potent growth inhibitors than were the corresponding myrrh extracts. The growth inhibition of the methanolic, ethyl acetate and hexane frankincense extracts against Salmonella salford was particularly noteworthy, with MIC values of 462, 258 and 293 µg/mL respectively. The frankincense and myrrh extracts were both approximately equally effective against gram positive and gram negative bacteria. The majority of the extracts also proved effective at blocking the proliferation of the colorectal cancer cell line CaCo2 and HeLa cervical cancer cell growth, although the aqueous and ethyl acetate frankincense extracts generally had the greatest efficacy (IC50 values 1600-1900 µg/mL). All extracts were non-toxic, with LC50 values substantially > 1000 µg/mL. Conclusion: These studies validate traditional usage of frankincense and myrrh in the treatment of several bacterial illnesses and some cancers, and indicate that they are safe for therapeutic usage.