Citation: Suciu, F.; Stoicescu, I.; Lupu, E.C.; Popescu, A.; Ros , ca, A.C.; Roncea, F.N.; Dumitrescu, D.-E.; Badea, V.; Badea, F.C. Antibacterial Activity of Lysimachia nummularia L. in Oro-Dental Diseases. Appl. Sci. 2023, 13, 6830. https://doi.org/ 10.3390/app13116830 Academic Editors: George Eliades and Liliana Sachelarie Received: 30 April 2023 Revised: 25 May 2023 Accepted: 3 June 2023 Published: 5 June 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). applied sciences Article Antibacterial Activity of Lysimachia nummularia L. in Oro-Dental Diseases Felicia Suciu 1,† , Iuliana Stoicescu 2, * ,† , Elena Carmen Lupu 3,† , Antoanela Popescu 4, * ,† , Adrian Cosmin Ros , ca 1,† , Florentina Nicoleta Roncea 5,† , Denisa-Elena Dumitrescu 6,† , Victoria Badea 7,† and Florin Ciprian Badea 8,† 1 Department of Analysis and Quality Control of Drugs, Faculty of Pharmacy, “Ovidius” University of Constanta, 900470 Constanta, Romania; felicia.suciu@365.univ-ovidius.ro (F.S.); cosmin.rosca@univ-ovidius.ro (A.C.R.) 2 Department of Chemistry and Quality Control of Drugs, Faculty of Pharmacy, “Ovidius” University of Constanta, 900470 Constanta, Romania 3 Department of Mathematics and Informatics, Faculty of Pharmacy, “Ovidius” University of Constanta, 900470 Constanta, Romania; clupu@univ-ovidius.ro 4 Department of Botanics, Faculty of Pharmacy, “Ovidius” University of Constanta, 900470 Constanta, Romania 5 Department of Pharmaceutical Technology, Faculty of Pharmacy, “Ovidius” University of Constanta, 900470 Constanta, Romania; florentina.roncea@univ-ovidius.ro 6 Department of Organic Chemistry, Faculty of Pharmacy, “Ovidius” University of Constanta, 900470 Constanta, Romania; denisa.dumitrescu@univ-ovidius.ro 7 Department of Microbiology and Immunology, Faculty of Dental Medicine, “Ovidius” University of Constanta, 900684 Constanta, Romania; victoria.badea@365.univ-ovidius.ro 8 Department of Dental Medicine, Faculty of Dental Medicine, “Ovidius” University of Constanta, 900684 Constanta, Romania; florin.badea@365.univ-ovidius.ro * Correspondence: iuliana.stoicescu@univ-ovidius.ro (I.S.); antoanela.popescu@univ-ovidius.ro (A.P.) † These authors contributed equally to this work. Abstract: The aim is to evaluate the antibacterial and antifungal properties of the extracts obtained from Lysimachia nummularia L. in order to be able to introduce these extracts into pharmaceutical products and obtain useful products in the infectious and antifungal pathology of the oro-dental cavity. Extracts from different parts of the studied species have been obtained and chemically characterized: the total polyphenols in 40% ethanolic extracts have been determined and the caffeic and chlorogenic acids and trans-resveratrol, bioactive compounds involved in the antimicrobial properties of the studied species, have been identified, separated, and quantitatively determined. The antibacterial and antifungal activities of the extract of Lisymachia nummularia L. were determined using the diffusion method against a set of bacteria isolated from samples from different patients with diseases of the oro-dental cavity. The extract of Lisymachia nummularia L. exhibited antimicrobial activity against Gram-positive bacteria more than Gram-negative, where the effect was weaker; however, it had no antifungal effects on Candida albicans. Another aspect that must be emphasized is that the best antibacterial results were obtained from the aerial segment of the plant, the part where the highest concentration of polyphenols was identified in the studies presented. These results indicate that the pharmacological effects of the studied bacterial species support the use of extracts in obtaining pharmaceutical products that can be used to optimize treatment schemes in oro-dental diseases. Keywords: Lisimachia nummularia L.; antibacterial activity; oro-dental diseases 1. Introduction There are many biologically active compounds from plant extracts that have been shown to have antibacterial properties and can potentially help in developing resistance against bacterial infections. These natural plant extracts can potentially be used in combi- nation with conventional antibiotics to enhance their effectiveness or as an alternative to antibiotics to reduce the risk of antibiotic resistance. Appl. Sci. 2023, 13, 6830. https://doi.org/10.3390/app13116830 https://www.mdpi.com/journal/applsci