Phenolic Secondary Metabolites and Antiradical and Antibacterial Activities of Different Extracts of <i>Usnea barbata</i> (L.) Weber ex F.H.Wigg from Călimani Mountains, Romania

• Main Authors: Violeta Popovici (Author), Laura Bucur (Author), Cerasela Elena Gîrd (Author), Antoanela Popescu (Author), Elena Matei (Author), Georgeta Camelia Cozaru (Author), Verginica Schröder (Author), Emma Adriana Ozon (Author), Ancuța Cătălina Fița (Author), Dumitru Lupuliasa (Author), Mariana Aschie (Author), Aureliana Caraiane (Author), Mihaela Botnarciuc (Author), Victoria Badea (Author)
• Format: Book
• Published: MDPI AG, 2022-07-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 10.3390/ph15070829; 1424-8247
• Keywords: <i>Usnea barbata</i> (L.) Weber ex F.H. Wigg extracts; phenolic secondary metabolites; usnic acid; polyphenols; DPPH free-radical scavenging activity; antibacterial activity; Medicine; R; Pharmacy and materia medica; RS1-441
• Source: Pharmaceuticals, Vol 15, Iss 7, p 829 (2022)

Phenolic compounds represent an essential bioactive metabolites group with numerous pharmaceutical applications. Our study aims to identify and quantify phenolic constituents of various liquid and dry extracts of <i>Usnea barbata</i> (L.) Weber ex F.H. Wigg (<i>U. barbata</i>) from Calimani Mountains, Romania, and investigate their bioactivities. The extracts in acetone, 96% ethanol, and water with the same dried lichen/solvent ratio (<i>w</i>/<i>v</i>) were obtained through two conventional techniques: maceration (<i>m</i>UBA, <i>m</i>UBE, and <i>m</i>UBW) and Soxhlet extraction (<i>d</i>UBA, <i>d</i>UBE, and <i>d</i>UBW). High-performance liquid chromatography with diode-array detection (HPLC-DAD) was performed for usnic acid (UA) and different polyphenols quantification. Then, the total phenolic content (TPC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging activity (AA) were determined through spectrophotometric methods. Using the disc diffusion method (DDM), the antibacterial activity was evaluated against Gram-positive and Gram-negative bacteria known for their pathogenicity: <i>Staphylococcus aureus</i> (ATCC 25923), <i>Streptococcus pneumoniae</i> (ATCC 49619), <i>Pseudomonas aeruginosa</i> (ATCC 27853), and <i>Klebsiella pneumoniae</i> (ATCC 13883). All extracts contain phenolic compounds expressed as TPC values. Five lichen extracts display various UA contents; this significant metabolite was not detected in <i>d</i>UBW. Six polyphenols from the standards mixture were quantified only in ethanol and water extracts; <i>m</i>UBE has all individual polyphenols, while <i>d</i>UBE shows only two. Three polyphenols were detected in <i>m</i>UBW, but none was found in <i>d</i>UBW. All <i>U. barbata</i> extracts had antiradical activity; however, only ethanol and acetone extracts proved inhibitory activity against <i>P. aeruginosa</i>, <i>S. pneumoniae</i>, and <i>S. aureus</i>. In contrast, <i>K. pneumoniae</i> was strongly resistant (IZD = 0). Data analysis evidenced a high positive correlation between the phenolic constituents and bioactivities of each <i>U. barbata</i> extract. Associating these extracts' properties with both conventional techniques used for their preparation revealed the extraction conditions' significant influence on lichen extracts metabolites profiling, with a powerful impact on their pharmacological potential.