Abstract
Despite intensified efforts to develop an effective antibiotic, S. aureus is still a major cause of mortality and morbidity worldwide. The multidrug resistance of bacteria has considerably increased the difficulties of scientific research and the concomitant emergence of resistance is to be expected. In this study we have investigated the in vitro activity of 15 ethanol extracts prepared from Moroccan medicinal plants traditionally used for treatment of skin infections. Among the tested species I. viscosa, C. oxyacantha, R. tinctorum, A. herba alba, and B. hispanica showed moderate anti-staphylococcal activity. However, R. alaternus showed promising growth-inhibitory effects against specific pathogenic bacteria especially methicillin-susceptible Staphylococcus aureus Panton-Valentine leucocidin positive (MSSA-PVL) and methicillin-resistant S. aureus (MRSA). The bioguided fractionation of this plant using successive chromatographic separations followed by nuclear magnetic resonance (NMR) and mass spectrometry (MS) including EIMS and HREIMS analysis yielded the emodin (1) and kaempferol (2). Emodin being the most active with MICs ranging between 15.62 and 1.95 µg/mL and showing higher activity against the tested strains in comparison with the crude extract, its mechanism of action and the structure-activity relationship were interestingly discussed. The active compound has not displayed toxicity toward murine macrophage cells. The results obtained in the current study support the traditional uses of R. alaternus and suggest that this species could be a good source for the development of new anti-staphylococcal agents.
Highlights
According to the WHO, 50,000 persons around the world are dying every day because of infectious diseases
We describe a bioguided fractionation of R. alaternus ethanolic extract leading to the isolation and characterization of anthraquinones and flavonoids, we report the compound which is most likely be involved in the antibacterial activity
The ethanolic extracts of B. hispanica and R. alaternus showed the best activity against all strains, with a more remarkable susceptibility of S. aureus (Sa) and methicillin-resistant S. aureus (MRSA) (ATCC29213) compared to SaPVL+ and MRSA348 (Table 1)
Summary
According to the WHO, 50,000 persons around the world are dying every day because of infectious diseases. In the World Health Report, more than 17 million deaths out of a total of 52 million were due to infectious diseases [1] Among many of these disorders, Staphylococcus aureus (S. aureus) is the main responsible pathogenic bacteria with a large clinical spectrum [2]. Duployez et al [3] have reported a fatal case of a young adult with COVID-19; the complication of viral infection has been linked to necrotizing pneumonia induced by S. aureus producing PVL. These toxigenic strains make S. aureus infections more dangerous requiring specific clinical treatment [4,5]. We describe a bioguided fractionation of R. alaternus ethanolic extract leading to the isolation and characterization of anthraquinones and flavonoids, we report the compound which is most likely be involved in the antibacterial activity
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