Enantioselective activity of usnic acid: a comprehensive review and future perspectives

Abstract

This review is focused on the comparison of the biological and pharmacological activities of usnic acid enantiomers. Most of the available data refer to (?)-usnic acid, while the left-handed isomer has been less often significantly studied. Special attention was paid to the experiments comparing both (?)-and (-)-usnic acid at the same time, the results of which indicated interesting differences, however no tendency as to which enantiomer was more potent could be observed. Nevertheless, more studies, especially on (-)-usnic acid, are needed to give a final explanation for the similarities and differences between both usnic acid enantiomers. These should be especially directed to steric structure-activity relationship of the enantiomers, tested under the same experimental conditions, which may help to explain the possible mechanisms of their actions.

Cladonia uncialis as a valuable raw material of biosynthetic compounds against clinical strains of bacteria and fungi

“…The antibacterial activity of C. uncialis extracts has been proven for the first time in our previous studies, in which we demonstrated a high activity of the C. uncialis acetone extract (CUE) on methicillin-resistant Staphylococcus aureus (MRSA) strains (Studzińska-Sroka et al, 2015). These interesting findings, as well as previous information about antimicrobial activity of UA (Galanty et al, 2012;Alahmadi et al, 2017;Galanty et al, 2019), prompted us to expand the study on the activity of CUE against clinical pathogenic strains responsible for skin and wound infections, which demonstrate resistance to antibiotics. In our research we also compared the cytotoxic effect of the tested substances by employing in vitro studies with human keratinocyte cell cultures (HaCaT).…”

“…The most known lichenic compound is usnic acid (UA), existing in two enantiomeric forms of which (+)-UA occurs more frequently (Cetin et al, 2008). Results of research carried out so far indicate a high antibacterial activity of UA, mainly against Gram-positive strains (Galanty et al, 2019). Most of studies on antibacterial activity of UA were focused on its (+) enantiomer, which usually demonstrated an increased activity in comparison to its (-) form (Galanty et al, 2012).…”

Nano- and Microcarriers as Drug Delivery Systems for Usnic Acid: Review of Literature

“…Further coating with sbPCL 50 was performed by physical adsorption of the polymer onto the surface of magnetic nanoparticles yielding a sample designated sbPCL 50 -MnFe 2 O 4 . Nanoparticle coating with pAcDED was carried out using two methods: (1) physical adsorption (same procedure as in the case of sbPCL 50 ), designated as pAcDED-MnFe 2 O 4 and (2) in situ polymerization and cross-linking of the monomer AcDED (previously adsorbed onto nanoparticles) with N,N methylenebisacrylamide, designated as pAcDED CL -MnFe 2 O 4 . For drug encapsulation, the uncoated and coated nanoparticles were kept in contact with an alkaline solution of usnic acid.…”

“…Investigations of biological activities of lichens and their secondary metabolites with potential medical relevance over the past decades have singled out usnic acid as one of the most prominent lichen substances. Usnic acid was the subject of a vast majority of studies, including the ones discussing this substance as an isolated compound [1] or as a part of the usnic acid-containing lichens extracts [2][3][4][5], as well as investigations dealing with chemical derivatives of usnic acid [6]. As the stated studies suggested, usnic acid or its derivatives possess various biological activities, such as antimicrobial against various bacteria, fungi and parasites, as well as antioxidant, cytotoxic (antitumor), neuroprotective, gastroprotective, cardioprotective, cytoprotective, immunostimulatory, anti-inflammatory and wound healing properties [1].…”

“…A renewed interest in usnic acid in recent years has been reflected not only in the growth of the number of publications (Figure 1), but also in several review articles dealing with its chemical [6] and biological properties, its toxicity [1,7] and also its potential pharmaceutical use [8]. With respect to the later, the present review focuses on the development of drug delivery systems (DDSs) aiming to stress the ways to overcome stated drawbacks, thereby increasing the therapeutic index of this drug by improving the efficacy and/or reducing the toxicity.…”