Animal husbandry and experimental procedures were in accordance with the EU Directive 2010/63/EU for animal experiments and approved by the national ethical committee for care and use of animals (approval ID A16320). Every effort was made to minimize animal suffering and the number of animals used. Seven-week-old male C57Bl/6J mice from Janvier Labs (Le Genest-Saint-Isle, France) were housed in polypropylene cages and maintained in a temperature- and humidity-controlled pathogen-free facility with a 12 h light-dark cycle abd ad libitum access to food and water. Mice were handled daily for 1 week before experiment onset to minimize stress reactions due to manipulation. Mice were fed with A04 diet (Safe, Augy, France). They were supplemented by gavage (feeding probe V0105040, ECIMED, Boissy-Saint-Leger, France) with S. lavandulaefolia essential oil encapsulated with acacia gum (83.3 mg/kg/day), or S. officinalis aqueous leaf extract (166.7 mg/kg/day) or a mix of both vegetal extracts (Cognivia™; 250 mg/kg/day) or water for the control group, each morning for two weeks. S. lavandulaefolia essential oil was characterized for its content in terpenoids (as eucalyptol, camphor, α-, β-pinene and others) and S. officinalis aqueous leaf extract was characterized for its content in polyphenols (as rosmarinic acid, apigenin glucosides, luteolin glucosides and others). The encapsulation of essential oil was performed using acacia gum in solution with a specific shear stress in order to create dispersed and stabilized small oil droplets of essential oil (1 to 5 µm). Finally, the combination of both extracts was done using exactly the same materials. After the first day of gavage, mice were subjected to a Y-maze test to evaluate the impact of an acute dose on long-term memory. After two weeks of gavage, mice were submitted to a Morris water maze to evaluate the impact of a chronic dose on learning and long-term memory. At the end of the behavioral protocol, mice were sacrificed, and the brain structures implicated in memory (hippocampus, prefrontal cortex) and red blood cells were collected and frozen at −80 °C.
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