Kalanchoe brasiliensisCambess., a Promising Natural Source of Antioxidant and Antibiotic Agents against Multidrug-Resistant Pathogens for the Treatment ofSalmonellaGastroenteritis

Abstract

Kalanchoe brasiliensisCambess. is a native Brazilian plant popularly known as “saião”, and the juice of its fresh leaves is traditionally used to treat several disorders, including inflammatory and infectious processes such as dysentery. The goals of this study were to characterize the phytochemical composition and investigate the antioxidant activity, the antibiotic effect, and the mode of action againstSalmonellaof the hydroethanolic extracts fromK. brasiliensisleaves collected in the summer and spring Brazilian seasons. These extracts had their chemical composition established by high-performance liquid chromatography with diode-array detection. Total phenolic and flavonoid contents were spectrophotometrically determined. 2,2-Diphenyl-1-picryl-hydrazyl radical scavenging, phosphomolybdenum reducing power andβ-carotene bleaching assays were carried out to evaluate the antioxidant capacity. Antibiotic potential was assessed by minimal inhibitory concentration against 8 bacterial ATCC® and 5 methicillin-resistantStaphylococcus aureusand 5Salmonellaclinical strains. The mode of action was investigated by time-kill, bacterial cell viability, and leakage of compounds absorbing at 280 nm assays againstSalmonella. Chromatographic profile and UV spectrum analyses suggested the significant presence of flavonoid type patuletin and eupafolin derivatives, and no difference between both periods of collection was noted. Significant amounts of total phenolic and flavonoid contents and a promising antioxidant capacity were observed. Hydroethanolic extracts (70%, summer and spring) were the most active against the tested Gram-positive and Gram-negative bacterial strains, showing the bacteriostatic action of 5000μg/mL. Time-kill data demonstrated that these extracts were able to reduce theSalmonellagrowth rate. Cell number was reduced with release of the bacterial content. Together, these results suggest thatK. brasiliensisis a natural source of antioxidant and antibacterial agents that can be applied in the research and development of new antibiotics for the treatment ofSalmonellagastroenteritis because they are able to interfere in theSalmonellagrowth, probably due to cell membrane damage.