Context: The ‘antimicrobial resistant era’ requires advances in the approaches and technologies to find new treatments. The enhancement of the antimicrobial activity of Commercially Available Drugs (CADs) by Natural Products (NPs) has successful mixtures (e.g., clavulanic acid and amoxicillin).
Objective: To systematically review reports of synergistic effects of CADs and NPs against opportunistic microbial strains from 2010 to April 2016.
Methods: The databases and search engines PubMed, Medline, Scifinder, Scopus, Science Direct and Google Scholar were systematically searched. Among the keywords utilized were: synergistic effects natural products and antibiotics, botanicals and antibiotics bioassays, plant extracts interaction with antibiotics and antibiotic adjuvant bioassays. Only synergistic results were tabulated and analyzed according to CADs, NPs and strains.
Results: A set of 76 studies that reported in vitro synergistic effects of CADs and NPs against gram-positive or gram- negative bacteria or fungi opportunistic strains was found. From the 60 reports on antibacterial adjuvants, the most frequent designs involved beta-lactamics or aminoglycosides against Methicillin Resistant Staphylococcus aureus. The assayed NPs encompassed extracts or fractions from 22 different species distributed worldwide (45% extracted with non-polar solvents) and 33 purified compounds (flavonoids, other polyphenols and alkaloids).
Conclusion: NPs as potential drug hits for antimicrobial adjuvants had been found and should continue in the drug discovery pipeline. The field certainly would benefit of advances in purification technologies, especially for polar extracts and bioassay platforms.