Citation: Has , , I.M.; Teleky, B.-E.; Szabo, K.; Simon, E.; Ranga, F.; Diaconeasa, Z.M.; Purza, A.L.; Vodnar, D.-C.; Tit, D.M.; Nit , escu, M. Bioactive Potential of Elderberry (Sambucus nigra L.): Antioxidant, Antimicrobial Activity, Bioaccessibility and Prebiotic Potential. Molecules 2023, 28, 3099. https://doi.org/10.3390/ molecules28073099 Academic Editors: Leontina Grigore-Gurgu, Enachi Elena and Iuliana Aprodu Received: 24 February 2023 Revised: 25 March 2023 Accepted: 28 March 2023 Published: 30 March 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/). molecules Article Bioactive Potential of Elderberry (Sambucus nigra L.): Antioxidant, Antimicrobial Activity, Bioaccessibility and Prebiotic Potential Ioana Mariana Has , 1 , Bernadette-Em ˝ oke Teleky 2,3 , Katalin Szabo 2,3 , Elemer Simon 2,3 , Floricuta Ranga 3 , Zorit , a Maria Diaconeasa 3 , Anamaria Lavinia Purza 4 , Dan-Cristian Vodnar 2,3, * , Delia Mirela Tit 4, * and Maria Nit , escu 5 1 Doctoral School of Biomedical Sciences, University of Oradea, 410087 Oradea, Romania 2 Institute of Life Sciences, University of Agricultural Sciences and Veterinary Medicine, 400372 Cluj-Napoca, Romania 3 Department of Food Science and Technology, University of Agricultural Sciences and Veterinary Medicine, 400372 Cluj-Napoca, Romania 4 Department of Pharmacy, Faculty of Medicine and Pharmacy, University of Oradea, 410028 Oradea, Romania 5 Department of Preclinical–Complementary Sciences, University of Medicine and Pharmacy “Carol Davila”, 050474 Bucharest, Romania * Correspondence: dan.vodnar@usamvcluj.ro (D.-C.V.); dtit@uoradea.ro (D.M.T.) Abstract: Due to its abundance of physiologically active ingredients, one of the oldest medicinal herbs, elderberry (EB) Sambucus nigra L., is beneficial for both therapeutic and dietary purposes. This study determined the bioaccessibility of the phenolic compounds and the prebiotic potential of the polyphenols from freeze-dried EB powder (FDEBP), along with the antioxidant and antimicrobial activities of this extract. The most significant phenolic compounds in black EB are represented by anthocyanins (41.8%), predominating cyanidin-sambubiosides and cyanidin-glucosides (90.1% of the identified anthocyanins). The FRAP assay obtained the highest antioxidant activity value (185 ± 0.18 μmol Fe 2+ /g DW). The most sensitive to the antimicrobial activity of the extract was proven to be Staphylococcus aureus, and Pseudomonas aeruginosa had the lowest minimum inhibitory concentration of 1.95 mg/mL. To determine the prebiotic potential of the polyphenols, the cell growth of five probiotic strains (Lactobacillus plantarum, L. casei, L. rhamnosus, L. fermentum and Saccharomyces boulardii) was tested. The influence on cell growth was positive for all five probiotic strains used. Overall, the most significant increase (p < 0.05) was recorded at 1.5% FDEBP, on S. boulardii with a growth index (GI) of 141.02%, very closely followed by GI at 0.5% and 1% concentrations. The stability of the total phenolic compounds through simulated gastronitestinal digestion was increased (93%), and the bioaccessibility was also elevated (75%). Keywords: elderberry; polyphenols; bioaccessibility; gastrointestinal digestion; prebiotic potential 1. Introduction Since prehistoric times, plants have been used for food and as remedies [1]. In recent years, the interest in food supplements and functional foods, which contain bioactive plant-based compounds, has continuously increased. Numerous scientific studies were carried out using different methods and revealed the benefits of products rich in bioactive compounds [2,3] for preventing and treating certain diseases, including cardiovascular and metabolic diseases, pathologies responsible for millions of deaths worldwide [4–7]. An important source of bioactive compounds, relatively little studied compared to other berries, is black elderberry (EB), Sambucus nigra L.—also known as elder, black elder, European elder, European black elder, and common elder; it is part of the family Adoxaceae, genus Sambucus, being a common species. It has three subspecies: S. nigra ssp. canadensis, S. nigra ssp. Cerulea and S. nigra ssp. nigra L., the latter being the European elder [8–10]. Molecules 2023, 28, 3099. https://doi.org/10.3390/molecules28073099 https://www.mdpi.com/journal/molecules