Pharmacognostic analyses and evaluation of the in vitro antimicrobial activity of Acmella oleracea (L.) RK Jansen (Jambu) floral extract and fractions

Acmella oleracea (L) RK Jansen is a typical plant species of Northern Brazil, used in gastronomy and in the Amazonian folk medicine of Para State as analgesic, to treat diseases of the mouth and throat. In industry, extracts of this genus have been used in oral hygiene products and in food compositions, as refreshing and flavoring agent, and is also used in cosmetics and toiletry. This paper reports the pharmacognostic characteristics of the herbal drug (flowers) and the in vitro antimicrobial effect of its ethanol extract (EEFAO) and fractions on pathogenic microorganisms present both in skin and in gastrointestinal tract of domestic animals. EEFAO Hexane, Chloroform, Ethyl Acetate and Methanol fractions at different concentrations (1000, 500, 250, 125, 62.5, 31.25, 15.62, 7.81 mg/mL) were tested against microorganisms (bacteria and fungus). The phytochemical characterization of A. oleracea extract and fractions indicates the presence of, probably, Spilanthol, detected by thin layer chromatography using Dragendorff Reagent. Chloroform fraction inhibited the growth of Salmonella typhi at a Minimum Inhibitory Concentration of 31.25 mg/mL and the microscopic analyses of young flowers demonstrates the presence of undifferentiated hypanthium and involucral bracts, cypselas and vascular bundles, structures also observed in other species of this genus. Quality parameters, including phytochemical description, reported in this work allow the identification and standardization of the flowers as herbal drug, whose microscopic description is very useful because it enables its micrographic characterization. The Chloroform fraction of EEFAO can inhibit the growth of Salmonella typhi making possible the use of A. oleraceae in phytomedicines or conservatives for foods.   Key words: Antimicrobial, phytotherapy, flowers pharmacognosy, Salmonella typhi.