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

Abstract

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 Usnea barbata (L.) Weber ex F.H. Wigg (U. barbata) from Calimani Mountains, Romania, and investigate their bioactivities. The extracts in acetone, 96% ethanol, and water with the same dried lichen/solvent ratio (w/v) were obtained through two conventional techniques: maceration (mUBA, mUBE, and mUBW) and Soxhlet extraction (dUBA, dUBE, and dUBW). 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: Staphylococcus aureus (ATCC 25923), Streptococcus pneumoniae (ATCC 49619), Pseudomonas aeruginosa (ATCC 27853), and Klebsiella pneumoniae (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 dUBW. Six polyphenols from the standards mixture were quantified only in ethanol and water extracts; mUBE has all individual polyphenols, while dUBE shows only two. Three polyphenols were detected in mUBW, but none was found in dUBW. All U. barbata extracts had antiradical activity; however, only ethanol and acetone extracts proved inhibitory activity against P. aeruginosa, S. pneumoniae, and S. aureus. In contrast, K. pneumoniae was strongly resistant (IZD = 0). Data analysis evidenced a high positive correlation between the phenolic constituents and bioactivities of each U. barbata 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.

Cereal Waste Valorization through Conventional and Current Extraction Techniques—An Up-to-Date Overview

“…The main shortcoming of the Soxhlet extraction method is that the extract is constantly heated at the solvent boiling point, which might have a negative effect on thermolabile compounds or, moreover, can led to the formation of artifacts, according to Seidel et al [ 41 ]. In line with this, recently, Popovici et al [ 42 ] showed that prolonged Soxhlet extraction (8 h at 100 °C) has diminished total phenolic content of the analyzed samples.…”

Design, Characterization, and Anticancer and Antimicrobial Activities of Mucoadhesive Oral Patches Loaded with Usnea barbata (L.) F. H. Wigg Ethanol Extract F-UBE-HPMC

“…The U. barbata dry ethanol extract was previously studied and proved to have significant pharmacological potential. Its secondary phenolic metabolites were quantified through HPLC-DAD; UBE has a total phenolic content of 573.234 ± 42.308 mg PyE/g, of which 108.742 ± 0.703 mg/g usnic acid, 0.605 ± 0.007 mg/g ellagic acid, and 0.870 ± 0.008 mg/g gallic acid [ 65 ]. Moreover, using UHPLC/ESI/MS/MS in negative mode, Salgado et al [ 89 ] identified other secondary metabolites with phenolic structures (depsides, depsidones, diphenyl ethers).…”

“…Paired t-test was used to establish the differences between samples and controls, and p < 0.05 was considered statistically significant. The principal component analysis (PCA) was performed using XLSTAT 2022.2.1. by Addinsoft (New York, NY, USA) [ 65 ].…”

In Vitro Anticancer Activity of Mucoadhesive Oral Films Loaded with Usnea barbata (L.) F. H. Wigg Dry Acetone Extract, with Potential Applications in Oral Squamous Cell Carcinoma Complementary Therapy

“…The dried lichen was ground in an LM 120 laboratory mill (PerkinElmer, Waltham, MA, USA) and passed through the no. 5 sieve [ 34 ]. The obtained moderately fine lichen powder (particle size ≤ 315 μm) was subjected to Soxhlet extraction in acetone at 55–60 °C for 8 h, followed by solvent evaporation; the method is described in a previously published study [ 34 ].…”

“…5 sieve [ 34 ]. The obtained moderately fine lichen powder (particle size ≤ 315 μm) was subjected to Soxhlet extraction in acetone at 55–60 °C for 8 h, followed by solvent evaporation; the method is described in a previously published study [ 34 ]. The U. barbata dry acetone extract (UBA) was preserved in a freezer (Sirge ® Elettrodomestici—SAC Rappresentanze, Torino, Avigliana, Italy) at −18 °C until used for mucoadhesive oral films preparation [ 34 ].…”