Chemical composition and biological activities of the extracts and secondary metabolites of lichens belonging to the genus Usnea, Parmeliaceae

Lichens represent a promising source of antimicrobial, cytotoxic and antioxidant agents. Their great pharmacological potential lies in the fact that they represent specific symbiotic organisms and thus possess natural roles allowing them to be highly adaptable to different environmental conditions. On the other hand, stated biological activities of lichens with prospective medicinal significance may be connected to their long-term use in traditional treatment of various ailments. Genus Usnea from the Parmeliaceae family is certainly one of the best studied in terms of chemical composition and biological properties of its extracts and/or isolated compounds. In the first part of the study, a detailed review of literature has been performed yielding a detailed report on the investigations of biological activities of the lichens belonging to this genus. In the second part of the study, chemical composition of the lichens from the genus was described and, additionally, a survey of the biological properties of the most representative secondary metabolites in these lichens has been reported. It could be concluded that the extracts and/or isolated compounds from the lichens belonging to the genus Usnea may be considered a valuable source of prospective drug candidates with potential clinical relevance

Evaluation of Anticancer and Antioxidant Activity of a Commercially Available CO2 Supercritical Extract of Old Man's Beard (Usnea barbata)

There is a worldwide ongoing investigation for novel natural constituents with cytotoxic and antioxidant properties. The aim of this study was to investigate chemical profile and stated biological activities of the supercritical CO2 extract (SCE) of old man's beard compared to the extracts obtained using the conventional techniques (Soxhlet extracts and macerate). The most abundant compound identified was usnic acid, which content was inversely proportional to the polarity of the solvent used and was the highest in the SCE, which was the sample revealing the highest cytotoxic activity in tested tumor cell lines (B16 mouse melanoma and C6 rat glioma), with lower IC50 values compared to pure usnic acid. Further investigations suggested both SCE and usnic acid to induce apoptosis and/ or autophagy in B16 and C6, indicating higher cytotoxicity of SCE to be related to the higher degree of ROS production. A good correlation of usnic acid content in the extracts and their antioxidant capacity was established, extricating SCE as the most active one. Presented results support further investigations of SCE of old man's beard as a prospective therapeutic agent with potential relevance in the treatment of cancer and/ or in oxidative stress-mediated conditions

Emulzija stabilizovana alkil poliglukozidnim emulgatorom kao potencijalni nosač za CO2-natkritični ekstrakt vrste Usnea barbata - procena stabilnosti, bezbednosti i efikasnosti topikalne formulacije

Antimicrobial activity of Usnea barbata especially against bacteria involved in pathogenesis of various skin conditions has been well documented in literature. Nevertheless, there are no papers dealing with formulation of its isolates into topical preparations for treatment of skin infections. In present study, alkyl polyglucoside (APG)-based vehicle was developed as carrier of U. barbata CO2-supercritical extract (U-SE) that demonstrated the best anti- microbial potential in preliminary screening. For comparison, chosen extract in the same concentration and using the same procedure was incorporated into a pharmacopoeial vehicle. Comparative evaluation of physicochemical stability, efficiency and safety proved APG-based vehicle to possess certain preferential features as carrier of U-SE compared to the reference one, composing a topical formulation with potential clinical relevance in treatment of skin infections.Antimikrobna aktivnost vrste Usnea barbata naročito protiv bakterija koje učestvuju u patogenezi različitih bolesti kože, dobro je dokumentovana u naučnoj literaturi. Uprkos tome, ne postoje radovi koji se bave formulacijom topikalnih preparata na bazi ovog lišaja namenjenih lečenju kožnih infekcija. U ovoj studiji, razvijena je podloga stablizovana alkil poliglukozidnim (APG) emulgatorom, kao potencijalni nosač za ekstrakt vrste U. barbata koji je pokazao najbolji antimikrobni potencijal u preliminarnom istraživanju nekoliko ekstrakata dobijenih upotrebom različitih ekstragenasa/postupaka. Radi poređenja, odabrani CO2-natkritični ekstrakt je inkorporiran u istoj koncentraciji (koja odgovara 2 mas.% usninske kiseline) i istim postupkom izrade u često korišćenu podlogu farmakopejskog kvaliteta, a zatim je sprovedeno uporedno istraživanje fizičko-hemijske stabilnosti, efikasnosti i bezbednosti na obe grupe uzoraka. Rezulati našeg istraživanja pokazali su da se razvijena podloga stabilizovana APG emulgatorom može smatrati pogodnim nosačem za CO2-natkritični ekstrakt vrste U. barbata, čineći topikalnu formulaciju sa potencijalnim kliničkim značajem u terapiji kožnih infekcija. Reološka istraživanja pokazala su zadovoljavajuću sposobnost emulzije stabilizovane APG emulgatorom da ostane fizički stabilna nakon dodatka CO2-natkritičnog ekstrakta vrste U. barbata, u poređenju sa farmakopejskom. Međutim, konduktometrijska merenja su pokazala određena neslaganja sa reološkim nala- zima, namećući potrebu za dodatnim istraživanjima radi konačne procene fizičke stabilnosti testiranih emulzionih sistema. Izmerene vrednosti pH tokom perioda od 90 dana čuvanja uzoraka na sobnoj temperaturi ukazale su na zadovoljavajuću preliminarnu hemijsku stabilnost svih uzoraka. Dalja istraživanja efikasnosti i bezbednosti pokazala su bolji antimikrobni potencijal uzoraka sa podlogom stabilizovanom APG emulgatorom u odnosu na tradicionalno upotrebljavanu farmakopejsku bazu poznatog kvaliteta. Zadovoljavajući preliminarni bezbedonosni profili su pokazani kako za uzorke stabilizovane APG emulgatorom tako i za referentne krem uzorke. Na osnovu navedenog, može se zaključiti da je istraživana podloga bazirana na APG emulgatoru pokazala određene povoljnije karakteristike kao nosač za CO2-natkritični ekstrakt vrste U. barbata u poređenju sa konvencionalno korišćenom podlogom, naročito uzimajući u obzir njene poboljšane senzorne karakteristike, kao osobinu koja je često odlučujuća za komplijansu pacijenata

Usnea barbata CO2-supercritical extract in alkyl polyglucoside-based emulsion system: contribution of Confocal Raman imaging to the formulation development of a natural product

Topical treatment of skin infections is often limited by drawbacks related to both antimicrobial agents and their vehicles. In addition, considering the growing promotion of natural therapeutic products, our objective was to develop and evaluate naturally-based emulsion system, as prospective topical formulation for skin infections-treatment. Therefore, alkyl polyglucoside surfactants were used for stabilization of a vehicle serving as potential carrier for supercritical CO2-extract of Usnea barbata, lichen with well-documented antimicrobial activity, incorporated using two protocols and three concentrations. Comprehensive physicochemical characterization suggested possible involvement of extract's particles in stabilization of the investigated system. Raman spectral imaging served as the key method in disclosing extract's particles potential to participate in the microstructure of the tested emulsion system via three mechanisms: (1) particle-particle aggregation, (2) adsorption at the oil-water interface and (3) hydrophobic particle-surfactant interactions. Stated extract-vehicle interaction proved to be correlated to the preparation procedure and extract concentration on one hand and to affect the physicochemical and biopharmaceutical features of investigated system, on the other hand. Thereafter, formulation with the best preliminary stability and liberation profile was selected for further efficiency and in vivo skin irritation potential evaluation, implying pertinent in vitro antimicrobial activity against G+ bacteria and overall satisfying preliminary safety profile