China 
Africa 
Explore chapters and articles related to this topic
Monographs of fragrance chemicals and extracts that have caused contact allergy / allergic contact dermatitis
Published in Anton C. de Groot, Monographs in Contact Allergy, 2021
Determining the quantitative composition of industrial oakmoss and other lichen extracts, either resinoids, absolutes or other extracts, is very difficult because of the intense chemical variability of the extracts and, more importantly, the lack of analytical reference compounds that are necessary to perform quantitative measurements by standardization (50). Usnic acid is one of the most common lichen substances. Whereas oakmoss resinoid may contain >15% usnic acid, the absolutes are practically free of it (50). The contents of atranol and chloroatranol in untreated oakmoss absolutes (atranol and chloroatranol not removed) have been reported to be in the ranges of 2.1–2.9% and 0.9–1.4%, respectively (50,70,80).
Secondary Metabolites from Lichen Genus (Ramalina Ach.): Applications and Biological Activities
Published in Megh R. Goyal, Durgesh Nandini Chauhan, Assessment of Medicinal Plants for Human Health, 2020
T. R. Prashith-Kekuda, K. S. Vinayaka
Species of Ramalina are capable of producing a variety of secondary metabolites, belonging to three major classes, namely: depsides, depsidones, and dibenzofurane. Usnic acid, a dibenzofurane, is the signature lichen substance found in almost all Ramalina species. Besides usnic acid, compounds, such as sekikaic acid, atranorin, and salazinic acid are among the commonly found metabolites in some Ramalina species. Some compounds are unique to certain Ramalina species.3,11,63,72,101,106 Chester and Elix15 revealed the presence of 4,4’-di-O-methylcryptochlorophaeic acid, 2-O-methylsekikaic acid, 2,4’-di-O-methylnorsekikaic acid, and 4’-O-methyl-paludosic acid in several Ramalina species. Biocompounds detected in some Ramalina species are listed in Table 13.2.
Management and prevention of drug resistant infections in burn patients
Published in Expert Review of Anti-infective Therapy, 2019
Roohi Vinaik, Dalia Barayan, Shahriar Shahrokhi, Marc G Jeschke
Similarly, fusidic acid is another potential candidate with efficacy primarily against gram-positive organisms – specifically, Staphylococcus spp., Streptococcus spp., and Corynebacterium spp. While interest in the drug declined due to discovery of more potent antibiotics, fusidic acid has become an attractive alternative due to the advent of antimicrobial resistance. Ulkür et al. demonstrate that 2% fusidic acid treatment in contaminated rat full-thickness burns is capable of eradicating MRSA [100]. Furthermore, numerous creams containing a combination of fusidic acid and antifungal agents have been developed, allowing for rapid and easy application in burn patients [99]. Usnic acid is another topical formulation that possesses antimicrobial activity against gram-positive biofilm-forming bacteria. Similar to fusidic acid, usnic acid is efficacious against MRSA and is capable of inhibiting multiple S. aureus strains at lower concentrations than other antibiotics (e.g. oxacillin, clindamycin) in vitro [101]. In addition to its antimicrobial activity, collagen-based films containing usnic acid demonstrated a diminished inflammatory reaction at 7 days post-burn and improvement in collagenization density by 14 days in a rat burn model [102].
Radiosensitizer effect of usnic acid on Biomphalaria glabrata embryos
Published in International Journal of Radiation Biology, 2018
F. T. J. Santos, W. N. Siqueira, M. L. O. Santos, H. A. M. F. Silva, J. L. F. Sá, T. S. Fernandes, N. H. Silva, E. J. França, E. B. Silva, A. M. M. A. Melo
Lichens, symbiotic associations between fungi and algae, are the source of a variety of bioactive compounds, mainly derived from their secondary metabolism and having applications in medicine, the textile industry, cosmetics and food (Kosanić et al. 2012; Manojlovic et al. 2012; Paudel et al. 2012). Usnic acid, dibenzofuran found in several species of lichens, is one of the most studied lichen metabolites and one of the few commercially available today. A number of biological activities are attributed to this metabolite, and its analgesic, antiviral, antiparasitic, antimicrobial, anti-inflammatory, antiproliferative, antitumor and antioxidant effects are reported (Shang et al. 2014; Su et al. 2014). Such characteristics make usnic acid a promising candidate for bioassays that can verify its radiosensitizing activity.
Usnic acid and its derivatives for pharmaceutical use: a patent review (2000–2017)
Published in Expert Opinion on Therapeutic Patents, 2018
Olga A. Luzina, Nariman F. Salakhutdinov
Usnic acid (1) has two optical isomers; both are isolated from many species of lichen by a simple procedure and with high optical purity. Both enantiomers possess interesting biological and pharmacological activities. The study on the biological effects of UA was initiated in the 1930s, but unfortunately, further pharmacological studies were terminated in 2008 due to its toxic side effects [17]. An analysis of the published patents about UA since 2000 indicated that this compound is employed often to treat various external imperfections (skin lesions), mostly targeting microorganisms. These studies were concerned with many kinds of diseases, including acne, scurf, seborrheic dermatitis, atopic dermatitis, and psoriasis. Many studies were conducted in order to improve the low bioavailability of UA. It has been repeatedly demonstrated that the so-called pharmacologically accessible form of the UA – sodium, potassium or copper (II) usnate – shows more pronounced antibacterial properties, with an IC50 several times lower. Often, the antibacterial action of salts takes a bactericidal character in contrast to the bacteriostatic one of UA itself. One more method designed to increase bioavailability is the use of a carrier to dissolve the UA and increase its percutaneous permeability. Several patents are devoted to this area, from the selection of the carrier to the creation of liposomes or a nanoscale pharmacological form. In addition, the successful use of UA in compositions for processing medical instruments or creating antibacterial coatings for them has been patented.