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OBJECTIVE: To verify the efficacy of citral in inducing sedation and anesthesia in silver catfish (Rhamdia quelen) and grass carp (Ctenopharyngodon idella) and to assess the safety of essential oil (EO) of Aloysia citriodora and citral in inducing and maintaining anesthesia in silver catfish. STUDY DESIGN: Clinical study, randomized, parallel, multi-arm with control group in target species. ANIMALS: A total of 96 juvenile and 72 adult silver catfish and 80 juvenile grass carp were used. METHODS: Silver catfish and grass carp were exposed to different concentrations of citral, 15-675 and 15-600 µL L-1, respectively, during the maximum period of 30 minutes to verify sedation and anesthesia induction and recovery times. In addition, for anesthetic induction, silver catfish were exposed to the EO of A. citriodora and citral at 225 µL L-1 for 3.5 minutes. Then, fish were transferred to an anesthesia maintenance solution at 50 µL L-1 for 10 minutes to assess hematologic and biochemical variables at 60 minutes, 2 and 6 days after treatment. RESULTS: Citral only induced sedation from 15, 25 and 40 µLL-1 in both species. Anesthesia without mortality was induced in silver catfish at 50-600 µL L-1 and grass carp at 75-450 µL L-1. At 675 and 600 µL L-1, mortality was recorded in silver catfish and grass carp, respectively. The EO of A. citriodora and citral were safe in inducing and maintaining anesthesia in silver catfish, with mean corpuscular hemoglobin concentration being the only variable that varied in relation to time and treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Citral was effective in inducing sedation and anesthesia in both species. In addition, A. citriodora EO and citral were safe in inducing and maintaining anesthesia in silver catfish. Both agents are promising substances for the development of new drugs for fish.

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In vitropropagation increases the supply and commercialisation of products of interest. For this, optimising the growing conditions and the composition of the culture medium is crucial to benefit the full development of the plants. Thus, the objective was to evaluate the in vitropropagation of Aloysia triphyllaon different culture media, with varying agar and sucrose concentrations. The experiment was conducted as a completely randomised design, 3×3×3 factorial scheme, with three culture media (MS, JADS and WPM), three sucrose concentrations (8, 10 and 12 g L-1) and three agar concentrations (15, 30 and 45 g L-1), with three replicates each and experimental units composed of one plant per replicate. After 25 days of cultivation, the fresh and dry mass of the plants, numbers of leaves, numbers of nodes, plant lengths, numbers of oxidised leaves, hyperhydricity and acclimatization percentages were evaluated. The WPM medium resulted in a reduced fresh mass, reflecting in the low hyperhydricity observed in the explants, and favoured the acclimatization of the plants. Thus, the WPM medium with sucrose (15 g L-1) and agar (12 g L-1) is recommended as the medium most suitable for the in vitroregeneration of Aloysia triphylla.

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Aloysia triphylla essential oil (EO) has antimicrobial activity on Staphylococcus aureus which is a pathogen responsible for severe infections and food contamination. The target of EO is mainly in the cytoplasmic membrane. In this work the mechanisms of action of the EO of A. triphylla on S. aureus were investigated. A. triphylla was collected from La Paz. The oil was analyzed by GC-MS. The antimicrobial effects were evaluated by MIC, MBC, killing time and TEM. MIC values were 23 μg/mL for 6.3 x 104 CFU/mL, 92 μg/mL for 5.71 x 105 CFU/mL and 180 μg/mL for 9 x 106 CFU/mL. The MBC was 5920 μg/mL for all cellular concentrations and it was necessary more time to kill bigger cell populations. Multilamellar and mesosome-like structures on the membrane were seen by TEM. A. triphylla oil is an antibacterial compound against S. aureus which main mechanism of action seems to be the cytoplasmic membrane disruption.

El aceite esencial (AE) de Aloysia triphylla posee actividad antimicrobiana contra Staphylococcus aureus, patógeno responsable de infecciones nosocomiales e alimenticias. El blanco de acción de los AE es la membrana citoplasmática. El mecanismo de acción del AE de A. triphylla sobre S. aureus fue investigado. El AE de A. triphylla (La Paz, Argentina) fue analizado por CG-EM. Se evaluó́ el efecto antimicrobiano por CIM, CBM, tiempo de muerte y MET. Los valores de CIM fueron 23 μg/mL para 6.3 x 104 UFC/mL, 92 μg/mL para 5.71 x 105 UFC/mL y 180 μg/mL para 9 x 106 UFC/mL. La CBM fue 5920 μg mL para todas las concentraciones celulares estudiadas. El tiempo de muerte fue determinado; necesitando mayor tiempo para matar una población celular elevada. Fueron observados por MET estructuras multilamerales y semejantes a mesosomas. El AE de A. triphylla es un potencial compuesto antibacteriano contra S. aureus donde su principal mecanismo de acción es por disrupción de la membrana citoplasmática.

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UNLABELLED: Exposure of silver catfish to 40 µL/L of the essential oil of Aloysia triphylla (AT) during in vivo transport delayed the onset and resolution of rigor mortis as well as the degradation of IMP into HxR compared to the control. The fish that were treated with 30 or 40 µL/L of AT received lower sensory demerit scores after 10 d of storage in ice compared to the control, and the fish that were treated with 40 µL/L of AT had a longer sensory shelf life than did the control. These results indicated that using AT as a sedative in the water in which the silver catfish were transported extended their freshness and increased their shelf life during refrigerated storage. PRACTICAL APPLICATION: Interest in natural anesthetics, such as Aloysia triphylla, has increased in the field of commercial aquaculture because they reduce the number of fish lesions acquired during capture, handling, and transportation. Fish sedated with the essential oil of A. triphylla at 40 µL/L during transport before slaughter exhibited a delay in the loss of freshness and an increased shelf life in ice. In addition to improving animal welfare before slaughter, the essential oil appears to be a promising product for improving fish conservation in the food industry.

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This study investigated the chemical composition of five different extracts of Aloysia triphylla and their activity against Aeromonas sp. The extracts were obtained from the dried leaves by pressurized CO2 extraction at 30, 50 and 70ºC, and 100, 150, and 200 bar, and analyzed by GC/FID and GC-MS. The antibacterial activity was assayed by the microdilution method. The tested microorganisms comprised seven Aeromonas isolates obtained from the kidney of infected silver catfish, Rhamdia quelen. The yield, chemical composition and antibacterial activity of the extracts were dependent on the extraction conditions. Mono and sesquiterpenoids were the major constituents of all the extracts and the highest extraction yield was obtained at 70ºC and 200 bar. A. triphylla presented moderate antibacterial activity against Aeromonas sp.

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Este estudo foi realizado com o objetivo de avaliar o teor do óleo essencial de cidrão [Aloysia triphylla (L´Hérit) Britton] em diferentes horários de colheita e processamentos pós-colheita. O delineamento utilizado foi inteiramente casualizado. As colheitas foram realizadas em três horários distintos (8 h, 12 h e 16 h), com três repetições. Os processamentos pós-colheita foram cinco: T1- folhas frescas fragmentadas em 1cm; T2- folhas frescas processadas em liquidificador; T3- folhas frescas inteiras; T4- folhas secas inteiras; T5- folhas secas pulverizadas em moinho, com três repetições. O óleo essencial de cada tratamento foi extraído pela técnica de hidrodestilação, utilizando o aparelho modificado de Clevenger, por uma hora e trinta minutos. Os horários de colheita quando se detectou maior teor de óleo foram 8 h e 16 h. Os maiores teores de óleo essencial foram encontrados em folhas frescas fragmentadas em 1cm, folhas frescas processadas em liquidificador, folhas frescas inteiras e folhas secas inteiras.

This study was carried out in order to evaluate the essential oil content of lemon verbena at different harvest times and post-harvest processings. The experimental design used was completely randomized. The harvested material was collected at three different hours (8:00, 12:00 and 16:00 pm), and it was taken three times. In post-harvest processings, three replications and five treatments were us do: 1 cm fresh leaf fragments, blended fresh leaves, whole fresh leaves, whole dry leaves and dry leaves ground in mill. The essential oil was determined in Clevenger's modified apparatus for 1 hour and 30 minutes. The periods of the day that detected high essential oil content were at 8:00 am and 16:00 pm. The high essential oil level was in 1 cm fresh leaf fragments, blender processed fresh leaves, whole fresh leaves and whole dry leaves.