Introduction:

Bacteria resistant to antibiotics are important due to great negative impact on both, human health and animal production. Currently, Staphylococcus aureus is considered one of the six main bacterial groups with the highest reports of emergence resistance around the world. On the other hand, for decades the use of medicinal plants, have been important source of bactericidal compounds; however, there are other kind of molecules with many antimicrobial mechanisms such as phenolic compounds; which as antiquorum sensing (AQS) effect. In the mexican traditional medicine the creole avocado leaves (Persea americana var drymifolia), have been used to treat various diseases involving bacterial infections. In this sense, it is possible to find compounds with antioxidant, bactericidal and AQS effects, which could help to eradicate infections of resistant strains. Thus, the aim of this study was to determine the effect of the total polyphenols of Persea americana var. drymifolia and its AQS activity on methicillin-resistant S. aureus strains (MRSA).

Methods:

Polyphenols were extracted by ultrasound-assisted extraction from leaves of 18 cultivars of mexican avocado and purified with Amberlite XAD-16. These polyphenols were functionally analyzed and evaluated against strains of S. aureus MRSA to determine their AQS effect on the Agr system.

Results:

Polyphenols extracted from mexican avocado leaves showed strong bactericidal activity. From the 18 cultivars tested, the Maria Elena variety had the highest effect, exhibiting a MIC of 116 μg∙mL-1 and MBC of 133 μg∙mL-1 against the MRSA μ3 strain. However, they also inhibit expression levels of the agr operon (P2 and P3) with respect to 16S rDNA gene. Futhermore, polyphenols showed good antioxidant activity and the presence of flavonoids and saponins was recorded.

Discussion and Conclusion:

Polyphenols extracted from mexican avocado leaves, mainly exhibit an important bactericidal activity, but also inhibited the expression of genes associated with the quorum sensing of S. aureus MRSA strains. In addition, they have a good antioxidant activity, which together could help counteract infections with resistant strains more efficiently. Hence, mexican avocado leaves are an important source of antioxidant, bactericidal and AQS metabolites.