Spilanthol content of Acmella oleracea subtypes and their bactericide and antibiofilm activities against Streptococcus mutans

This study aimed to determine the extractive yield, the spilanthol content and the bactericide and antibiofilm activities of aqueous and hydroethanolic extracts of two regional variations (Amapa and Para) of Acmella oleracea (L.) R. K. Jansen against the cariogenic bacteria Streptococcus mutans. Aqueous extracts of leaves and hydroethanolic extracts of leaves and stems were obtained and submitted to UHPLC-ESI-QToF-MS/MS characterization. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extracts were determined using the microdilution method, while the crystal violet assay was used to access the activity over S. mutans pre-formed 1-day biofilms. The aqueous extracts of the leaves showed higher extractive yields compared to the hydroethanolic solutions. Nonetheless, the hydroethanolic mixture ensured a higher extraction of spilanthol. For instance, the leaves of Para variation (EELAO-PA) (99.97%) and the stem of Amapa variation (EESAO-AP) (99.17%) presented the highest spilanthol content. Therefore, these extracts were selected for the antimicrobial assays, presenting equally MIC and MBC of 125 mg/ml against S. mutans. In the antibiofilm assay, EELAO-PA at 500 mg/ml (4xMIC) presented an inhibition of 50.89% after a 1 minute single application, similarly (p>0.05) to that found after chlorhexidine gluconate 0.12% treatment. Accordingly, A. oleracea rich spilanthol extracts showed remarkable antibacterial activity against the cariogenic S. mutans and could become an affordable coadjuvant used in dental products to prevent and control dental caries. (C) 2021 SAAB. Published by Elsevier B.V. All rights reserved.