Abstract
In view of the increasing interest in natural antimicrobial molecules, this study screened the ability of Thymus capitatus (TC) essential oil and Citrus limon var. pompia (CLP) extract as raw extracts or incorporated in vesicular nanocarriers against Streptococcus mutans and Candida albicans. After fingerprint, TC or CLP were mixed with lecithin and water to produce liposomes, or different ratios of water/glycerol or water/propylene glycol (PG) to produce glycerosomes and penetration enhancer vesicles (PEVs), respectively. Neither the raw extracts nor the nanovesicles showed cytotoxicity against human gingival fibroblasts at all the concentrations tested (1, 10, 100 μg/mL). The disc diffusion method, MIC-MBC/MFC, time-kill assay, and transmission electron microscopy (TEM) demonstrated the highest antimicrobial potential of TC against S. mutans and C. albicans. The very high presence of the phenol, carvacrol, in TC (90.1%) could explain the lethal effect against the yeast, killing up to 70% of Candida and not just arresting its growth. CLP, rich in polyphenols, acted in a similar way to TC in reducing S. mutans, while the data showed a fungistatic rather than a fungicidal activity. The phospholipid vesicles behaved similarly, suggesting that the transported extract was not the only factor to be considered in the outcomes, but also their components had an important role. Even if other investigations are necessary, TC and CLP incorporated in nanocarriers could be a promising and safe antimicrobial in caries prevention.
Highlights
As proposed in the “ecological plaque hypothesis”, a carious lesion develops under changed environmental conditions, producing a corresponding disturbance to the stability of the resident microflora [1]
In view of the increasing general interest in developing antimicrobials of natural origins, which could, be useful in caries prevention, this study aimed to assess the antimicrobial efficacy of Thymus capitatus (TC) essential oil and Citrus limon var. pompia (CLP) extract used as raw extracts or incorporated in vesicular nanocarriers in the neutralization of S. mutans and C. albicans
The results demonstrated that the inoculum of S. mutans was reduced to 11% within 3 h after the addition of raw TC essential oil; and C. albicans’ viability was inhibited to 30% after 3 h of exposure to the raw oil
Summary
As proposed in the “ecological plaque hypothesis”, a carious lesion develops under changed environmental conditions, producing a corresponding disturbance to the stability of the resident microflora [1]. Changes occur when the frequency of fermentable dietary carbohydrate intake is increased. In such a situation, the biofilm spends more time at low pH, allowing Streptococcus mutans to proliferate at the expense of the resident community. S. mutans contributes to the lowering of the pH and the growth of acidogenic species at the expense of the resident microflora [2,3]. This breakdown disrupts the de- and remineralization in teeth, pushing the equilibrium toward demineralization and tooth cavities. Candida albicans can appear in cariogenic biofilm when bonded to S. mutans, increasing the virulence of the biofilm and resulting in severe and recurrent caries in early childhood [4] and in salivary disorders [5]
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