Antibacterial activity of Lippia alba, Myrcia lundiana and Ocimum basilicum essential oils against six food-spoiling pathogenic microorganisms / Actividad antibacteriana de los aceites esenciales de Lippia alba, Myrcia lundiana y Ocimum basilicum contra seis microorganismos patógenos que estropean los alimentos

The aim of this study was to undertake a screening experiment on essential oils (EO) of Myrcia lundiana, Ocimum basilicum and Lippia alba against six food-spoiling pathogenic bacteria. Seventy-two (72) samples were initially analyzed fo antimicrobial activity based on the agar diffusion test. The minimum inhibitory (MIC) and bactericidal (MBC) concentrations were determined for the 12 samples which showed greatest antimicrobial potential in this stage. Two samples of L. alba, three samples of M. lundiana and seven samples of O. basilicum showed a MIC of 0.12-125 µL/mL for the six tested bacteria. Of these, the EO of O. basilicum cultivar Maria Bonita stood out with the lowest MIC and MBC. Thus, a mixture simulating this essential oil was prepared from commercial standards of the compounds (±)-linalool, geraniol and 1,8-cineole. Significantly higher MIC and MBC were detected in the simulation compared to the respective EO, suggesting a synergistic effect between compounds.

El objetivo de este estudio fue realizar un experimento de detección en aceites esenciales (AE) de Myrcia lundiana, Ocimum basilicum y Lippia alba contra seis bacterias patógenas que estropean los alimentos. Setenta y dos (72) muestras fueron analizadas inicialmente para la actividad antimicrobiana basada en la prueba de difusión en agar. Se determinaron las concentraciones mínimas inhibitoria (CMI) y bactericida (CMB) para las 12 muestras que mostraron el mayor potencial antimicrobiano en esta etapa. Dos muestras de L. alba, tres muestras de M. lundiana y siete muestras de O. basilicum mostraron un CMI de 0.12-125 µL/mL para las seis bacterias analizadas. De estos, el AE de O. basilicum cultivar Maria Bonita se destacó con el CMI y CMB más bajos. Por lo tanto, se preparó una mezcla que simula este aceite esencial a partir de los estándares comerciales de los compuestos de (±)-linalol, geraniol y 1,8-cineol. Se detectaron CMI y CMB significativamente más altos en la simulación en comparación con el AE respectivo, lo que sugiere un efecto sinérgico entre los compuestos.

Chemical characterization of the essential oil from leaves of basil genotypes cultivated in different seasons / Caracterización química del aceite esencial de hojas genotipos de albahaca cultivados en diferentes estaciones del año

The aim of this study was to evaluate the concentration and chemical composition of the essential oil the leaves of basil cultivars and hybrids cultivated in different cropping seasons: dry season and rainy season. The variables evaluated were the content and composition of essential oils in the two seasons. The essential oil content ranged from 0.66% to 3.21% in the dry season and from 0.80% to 4.20% in the rainy season. The major compounds found among the genotypes were linalool, methyl chavicol, neral, geranial, eugenol, and methyl (E)- cinnamate, defining the formation of five groups in each season, classified in the following chemotypes: methyl chavicol (Group 1), citral (neral+geranial) (Group 2), methyl cinnamate (Group 3), linalool (Group 4), and intermediate linalool (Group 5). All the traits evaluated had heritability (h ) greater than 95% and high CVg/CVe ratio values. The cropping season affected the content and chemical compositions of basil essential oil.

El objetivo de este estudio fue evaluar la concentración y composición química del aceite esencial las hojas de cultivares de albahaca e híbridos cultivados en diferentes temporadas de cultivo: estación seca y estación lluviosa. Las variables evaluadas fueron la contenido y la composición de los aceites esenciales en las dos estaciones. La contenido de aceite esencial varió de 0.66% a 3.21% en la estación seca y de 0.80% a 4.20% en la estación lluviosa. Los principales compuestos encontrados entre los genotipos fueron linalool, metilchavicol, neral, geranial, eugenol y metil (E)-cinamato, definiendo la formación de cinco grupos en cada estación, clasificados en los siguientes quimiotipos: metil chavicol (Grupo 1), citral (neral + geranial) (Grupo 2), cinamato de metilo (Grupo 3), linalool (Grupo 4) y linalol intermedio (Grupo 5). Todos los rasgos evaluados mostraron una heredabilidad (h ) mayor que el 95% y altos valores de relación CVg/CVe. La temporada de cultivo afectó la contenido y las composiciones químicas del aceite esencial de albahaca.

Water deficit and seasonality study on essential oil constituents of Lippia gracilis Schauer germplasm.

The aim of this study was to analyze the chemical composition of the essential oil from leaves of Lippia gracilis genotypes, in the dry and rainy seasons, and with and without irrigation. The extraction of essential oil was realized by hydrodistillation in a Clevenger apparatus. The chemical composition analysis was performed using a GC-MS/FID. The leaves of the L. gracilis genotypes provide essential oil with content between 1.25% and 1.92% in the rainy season and 1.42% and 2.70% in the dry season; when irrigation was used the content was between 1.42% and 2.87%, without irrigation contents were between 1.60% and 3.00%. The chemical composition of L. gracilis showed high levels of terpenes. The major constituent of genotypes LGRA-106 was thymol and carvacrol was the major constituent for the other genotypes. Concentrations showed little variation between seasons, demonstrating the stability of the chemical composition of L. gracilis even with different climatic conditions.

Acaricidal activity of Lippia gracilis essential oil and its major constituents on the tick Rhipicephalus (Boophilus) microplus.

The present study aimed to evaluate the activity of Lippia gracilis Schauer essential oil obtained from different L. gracilis genotypes and their major components, carvacrol and thymol against Rhipicephalus (Boophilus) microplus (cattle tick) larvae and engorged females. The larval test was performed parallel to the adult immersion test for engorged females for four L. gracilis genotypes. Similar tests were further performed for their major compounds carvacrol and thymol. Carvacrol (LC50 of 0.22 and 4.46 mg/mL, to larvae and engorged females, respectively) was more efficient than thymol (LC50 of 3.86 and 5.50 mg/mL, to larvae and engorged females, respectively). The lethal concentrations obtained for the isolated essential oil from genotypes LGRA-201 against larvae (1.31 mg/mL) and LGRA-106 against engorged females (4.66 mg/mL) confirmed the acaricidal activity of L. gracilis essential oil and its effectiveness in controlling the southern cattle tick.