Bactericidal Activity of Carvacrol against <i>Streptococcus pyogenes</i> Involves Alteration of Membrane Fluidity and Integrity through Interaction with Membrane Phospholipids
Background: Carvacrol, a mono-terpenoid phenol found in herbs, such as oregano and thyme, has excellent antibacterial properties against <i>Streptococcus pyogenes</i>. However, its mechanism of bactericidal activity on <i>S. pyogenes</i> has not been elucidated. Objectives: T...
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| Main Authors: | , , , , , |
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| Format: | Book |
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MDPI AG,
2022-09-01T00:00:00Z.
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| Summary: | Background: Carvacrol, a mono-terpenoid phenol found in herbs, such as oregano and thyme, has excellent antibacterial properties against <i>Streptococcus pyogenes</i>. However, its mechanism of bactericidal activity on <i>S. pyogenes</i> has not been elucidated. Objectives: This study investigated the bactericidal mechanism of carvacrol using three strains of <i>S. pyogenes</i>. Methods: Flow cytometry (FCM) experiments were conducted to determine carvacrol's membrane permeabilization and cytoplasmic membrane depolarization activities. Protoplasts of <i>S. pyogenes</i> were used to investigate carvacrol's effects on the membrane, followed by gel electrophoresis. The carvacrol-treated protoplasts were examined by transmission electron microscopy (TEM) to observe ultrastructural morphological changes. The fluidity of the cell membrane was measured by steady-state fluorescence anisotropy. Thin-layer chromatographic (TLC) profiling was conducted to study the affinity of carvacrol for membrane phospholipids. Results: Increased membrane permeability and decreased membrane potential from FCM and electron microscopy observations revealed that carvacrol killed the bacteria primarily by disrupting membrane integrity, leading to whole-cell lysis. Ultra-structural morphological changes in the membrane induced by carvacrol over a short period were confirmed using the <i>S. pyogenes</i> protoplast and membrane isolate models in vitro. In addition, changes in the other biophysical properties of the bacterial membrane, including concentration- and time-dependent increased fluidity, were observed. TLC experiments showed that carvacrol preferentially interacts with membrane phosphatidylglycerol (P.G.), phosphatidylethanolamine (P.E.), and cardiolipins (CL). Conclusions: Carvacrol exhibited rapid bactericidal action against <i>S. pyogenes</i> by disrupting the bacterial membrane and increasing permeability, possibly due to affinity with specific membrane phospholipids, such as P.E., P.G., and CL. Therefore, the bactericidal concentration of carvacrol (250 µg/mL) could be used to develop safe and efficacious natural health products for managing streptococcal pharyngitis or therapeutic applications. |
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| Item Description: | 10.3390/pharmaceutics14101992 1999-4923 |