Chemical Composition and Antimicrobial Activity of Essential Oil and Hydrosol Extract From Roots of Plumbago europaea and in-vitro Combinatory Antimicrobial Effect of Hydrosol Extract with Gentamicin and Amphotericin B

Background: Infectious diseases are responsible for millions of deaths a year worldwide. Antibiotics, which have saved so many lives and improved life expectancy, may become ineffective due to a worrying increase in bacterial resistance. Some of the appropriate actions that could be initiated to address this problem are to develop and search for new antimicrobial substances from medicinal plants, and combine antibiotics with antimicrobials agents isolated from a reservoir of bioactive natural products. Objectives: The purpose of this work was to study the chemical composition of the essential oil and hydrosol extract of Plumbago europaea, to evaluate their in-vitro antimicrobial activities and evaluate in-vitro combinatory antimicrobial effect of hydrosol extract with Gentamicin and Amphotericin B against a large panel of microorganisms in an effort to reduce their minimum effective dose and minimizing their side effects. Methods: The essential oil and hydrosol extract obtained from roots of Plumbago europaea were analyzed by GC/MS and tested for their antibacterial and antifungal activities against twelve different strains of microorganisms. The effectiveness, in-vitro, of the association between the hydrosol extract and both Gentamicin and Amphotericin B was also investigated using the checkerboard method. Results: The obtained results revealed that nine and four components, representing for 92.4 % and 97.4% of the total essential oil and hydrosol extract composition were identified, respectively and hydrosol extract was more active than the essential oil against all screened microorganisms, with interesting MIC values (19 μg/mL). An important effect of hydrosol extract was obtained in decreasing the MIC of Gentamicin and Amphotericin B in all tested combinations. Conclusion: The in-vitro combination of the hydrosol extract with Gentamicin and Amphotericin B led to substantial MIC reduction against all tested microorganisms. This combination can help to reduce the minimum effective dose of antimicrobial drugs used, which may help to decrease their side effects; and deliver these medicines with similar potency.