Abstract 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.

Resumen Introducción: La resistencia a los antibióticos por parte de las bacterias está provocando gran impacto negativo en la salud humana y en la producción animal. Actualmente, Staphylococcus aureus es considerada dentro de los seis principales grupos bacterianos con mayores reportes de aparición de resistencia a nivel mundial. Por otro lado, durante décadas las plantas de uso medicinal han sido fuente importante de compuestos bactericidas; sin embargo, también se ha empezado a documentar otras moléculas con otros mecanismos antimicrobianos, como es la inhibición de la percepción de quórum (anti-percepción de quórum (APQ)). En la medicina tradicional mexicana las hojas de aguacate mexicano (Persea americana var drymifolia) han sido empleadas para tratar diversos padecimientos que involucran infecciones bacterianas, por lo que es factible contenga compuestos que posean efectos antioxidantes, bactericidas y APQ, que ayuden a combatir las infecciones de cepas resistentes. De tal manera, que el objetivo de esta investigación fue determinar el efecto de los polifenoles totales de las hojas de Persea americana var. drymifolia y su actividad APQ sobre cepas de S. aureus resistentes a meticilina (MRSA). Métodos: Se obtuvieron los polifenoles presentes en las hojas de 18 cultivares de aguacate mexicano mediante extracción asistida por ultrasonido y fueron purificados en una columna de amberlita. Estos polifenoles fueron analizados funcionalmente y evaluados contra cepas de S. aureus MRSA para determinar su efecto APQ sobre el sistema denominado Agr. Resultados: Los polifenoles extraídos de las hojas de aguacate de raza mexicana exhiben una fuerte actividad bactericida. De los 18 cultivares probados, la variedad María Elena fue la que presentó el mayor efecto, exhibiendo una CMI de 116 μg∙mL-1 y un CMB de 133 μg∙mL-1 contra la cepa de MRSA μ3. Sin embargo, también logran inhibir los niveles de expresión del operón agr (P2 y P3) con respecto al gen constitutivo de rDNA 16S. De igual manera, los polifenoles mostraron una buena actividad antioxidante, además de que se logró identificar la presencia de flavonoides y saponinas. Discusión y Conclusión: Los polifenoles extraídos de las hojas de aguacate mexicano, exhiben principalmente actividad bactericida, pero también inhiben la expresión de genes asociados a la percepción de quórum de cepas de S. aureus MRSA. De igual manera, presentan una buena actividad antioxidante, lo que en conjunto puede ayudar a contrarrestar las infecciones con cepas resistentes de manera más eficiente. Por lo tanto, las hojas de aguacate mexicano son una fuente importante de metabolitos antioxidantes, bactericidas y APQ.

The effects of the aging process and an active life-style on the autonomic control of heart rate (HR) were investigated in nine young sedentary (YS, 23 ± 2.4 years), 16 young active (YA, 22 ± 2.1 years), 8 older sedentary (OS, 63 ± 2.4 years) and 8 older active (OA, 61 ± 1.1 years) healthy men. Electrocardiogram was continuously recorded for 15 min at rest and for 4 min in the deep breathing test, with a breath rate of 5 to 6 cycles/min in the supine position. Resting HR and RR intervals were analyzed by time (RMSSD index) and frequency domain methods. The power spectral components are reported in normalized units (nu) at low (LF) and high (HF) frequency, and as the LF/HF ratio. The deep breathing test was analyzed by the respiratory sinus arrhythmia indices: expiration/inspiration ratio (E/I) and inspiration-expiration difference (deltaIE). The active groups had lower HR and higher RMSSD index than the sedentary groups (life-style condition: sedentary vs active, P < 0.05). The older groups showed lower HFnu, higher LFnu and higher LF/HF ratio than the young groups (aging effect: young vs older, P < 0.05). The OS group had a lower E/I ratio (1.16) and deltaIE (9.7 bpm) than the other groups studied (YS: 1.38, 22.4 bpm; YA: 1.40, 21.3 bpm; OA: 1.38, 18.5 bpm). The interaction between aging and life-style effects had a P < 0.05. These results suggest that aging reduces HR variability. However, regular physical activity positively affects vagal activity on the heart and consequently attenuates the effects of aging in the autonomic control of HR.

Reported here are the in situ FT-IR and 13C-NMR spectroscopic studies of the complex cis-[Ir(CO)2(py)2](PF6 ) (py = pyridine) dissolved in 80% aqueous pyridine used as a precursor in the homogeneous catalysis of the water gas shift reaction (WGSR, CO + H2O Æ CO2 + H2). These spectroscopy studies reveal the presence of aminocarbonyliridium complexes with linear and bridging carbonyls groups as reaction intermediates. The WGSR catalysis by Ir4(CO)12 complex dissolved in 80% of aqueous 4-picoline or pyridine under 1.9 atm of CO at 100 C and the FT-IR and ¹H-NMR in situ studies of the pyridine promoted disproportionation of Ir4(CO)12, are also described