Abstract
Plant compounds are a potential source of new antimicrobial molecules against a variety of infections. Plant extracts suppose complex phytochemical libraries that may be used for the first stages of the screening process for antimicrobials. However, their large variability and complexity require fast and inexpensive methods that allow a rapid and adequate screening for antimicrobial activity against a variety of bacteria and fungi. In this study, a multi-well plate assay using the AlamarBlue® fluorescent dye was applied to screen for antimicrobial activity of several botanical extracts and the data were correlated with microbial colony forming units (CFU). This correlation was performed for three pathogenic model microorganisms: Escherichia coli (Gram negative bacteria), Staphylococcus aureus (Gram positive bacteria) and for the yeast-like fungi Candida albicans. A total of ten plant extracts from different Mediterranean plants, including several Cistus and Hibiscus species, were successfully tested. HPLC-DAD-ESI-MS/MS analysis was utilized for the characterization of the extracts in order to establish structure-activity correlations. The results show that extracts enriched in ellagitannins and flavonols are promising antibacterial agents against both Gram positive and Gram negative bacteria. In contrast, phenolic acids, anthocyanidins and flavonols may be related to the observed antifungal activity.
Highlights
Despite the numerous advances made in medicine and pharmacology, there is still a need for new antimicrobial agents, especially due to outbreak of multi-drug-resistant forms of both Gram negative and Gram positive bacteria to front-line antibiotics [1,2,3,4]
The following antibacterial agents were applied in the positive assay controls: kanamycin 50 μg/mL, tetracycline 15 μg/mL, (Sigma-Aldrich product # K-4000, T-7660), ampicillin 50 μg/mL (GIBCO-Life Technologies cat# 11593–027)
The first step was to validate microplate AlamarBlue assay (MABA) as an adequate screening method for testing antimicrobial activity based on bacterial growth monitoring
Summary
Despite the numerous advances made in medicine and pharmacology, there is still a need for new antimicrobial agents, especially due to outbreak of multi-drug-resistant forms of both Gram negative and Gram positive bacteria to front-line antibiotics [1,2,3,4]. Antibiotic resistance has become one of the major sanitary problems worldwide and disseminate rapidly amongst patients in healthcare facilities. Resistant bacteraemia rates seemed to decrease in several EU countries within the past years, the European Medicine Agency (EMA) estimates that. Screening for New Antimicrobial Compounds using a HTS Method. 30038, Fisiopatologia de la Obesidad y la Nutricion, CIBERobn, Instituto de Salud Carlos III). We would like to state that the funder Invitrotecnia S.L. only provided support in the form of salaries for author EBC, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript
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