Phytochemical screening of extracts from Spiranthera odoratissima A. St.-Hil. (Rutaceae) leaves and their in vitroantioxidant and anti-Listeria monocytogenes activities

Spiranthera odoratissima A. St.-Hil (Rutaceae), a shrub whose common name is manacá do Cerrado in Brazilian Portuguese, is about 1-m high and has been used by folk medicine to treat stomachache, kidney and liver infections, headache, rheumatism and as a blood purifier. This study aimed at preparing hexane, ethyl acetate, methanolic, hydroethanolic and aqueous extracts from S. odoratissima leaves, at carrying out preliminary phytochemical screening and at evaluating their in vitroantioxidant and anti-Listeria monocytogenesactivities. Antioxidant activity was evaluated by the DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2-azinobis-3-ethybenzothiazoline-6-sulfonate) and FRAP (ferric reducing antioxidant power) methods. Antibacterial activity was investigated against L. monocytogenesand Minimum Inhibitory Concentration (MIC) values of plant extracts were calculated by the broth microdilution method with the use of 96-well plates. In aqueous, methanolic, hydroethanolic, ethyl acetate and hexane extracts from S. odoratissima leaves, the following classes of compounds were investigated: organic acids, reducing sugars, flavonoids, saponin compounds, coumarin compounds, phenolics, tannins, purine compounds, catechins, flavonol derivatives, sesquiterpene lactonesand anthraquinones. All plant extracts, except the hexane one, exhibited high antioxidant activity. Regarding antibacterial activity, the most polar extracts showed high activity against L. monocytogenes; their MIC values ranged between 12.5 and 62.5 μg mL-1, while the hexane one exhibited low activity (MIC = 1000 μgmL-1). In short, extracts from S. odoratissima leaves may be consideredpromising sources of secondary metabolites with relevant antioxidant and antibacterial activities.

Occurrence and antimicrobial resistance patterns of Listeria monocytogenes isolated from vegetables

Although the consumption of fresh and minimally processed vegetables is considered healthy, outbreaks related to the contamination of these products are frequently reported. Among the food-borne pathogens that contaminate vegetables is Listeria monocytogenes, a ubiquitous organism that exhibits the ability to survive and multiply at refrigerated temperatures. This study aimed to evaluate the occurrence of L. monocytogenes in vegetables as well as the antimicrobial resistance of isolates. The results showed that 3.03% of samples were contaminated with L. monocytogenes, comprising 2.22% of raw vegetables and 5.56% of ready-to-eat vegetables. Multiplex PCR confirmed the virulence potential of the isolates. Antimicrobial resistance profiling showed that 50% of the isolates were susceptible to the antibiotics used. The resistance of one isolate to penicillin G, a commonly employed therapeutic agent, and the presence of serotype 4b, a serotype commonly associated with food-borne outbreaks, could be potential health hazards for consumers.(AU)