Resorcinol (or resorcin) is a phenolic compound. It is an organic compound with the formula C6H4(OH)2. It is one of three isomeric benzenediols, the 1,3-isomer (or meta-isomer). Resorcinol crystallizes from benzene as colorless needles that are readily soluble in water, alcohol, and ether, but insoluble in chloroform and carbon disulfide.
The Parmeliaceae is a large and diverse family of Lecanoromycetes. With over 2700 species in 71 genera, it is the largest family of lichen-forming fungi. The most speciose genera in the family are the well-known groups: Xanthoparmelia, Usnea, Parmotrema, and Hypotrachyna.
The Dakin oxidation (or Dakin reaction) is an organic redox reaction in which an ortho- or para-hydroxylated phenyl aldehyde (2-hydroxybenzaldehyde or 4-hydroxybenzaldehyde) or ketone reacts with hydrogen peroxide (H2O2) in base to form a benzenediol and a carboxylate. Overall, the carbonyl group is oxidised, whereas the H2O2 is reduced.
Topoisomerase inhibitors are chemical compounds that block the action of topoisomerases, which are broken into two broad subtypes: type I topoisomerases (TopI) and type II topoisomerases (TopII). Topoisomerase plays important roles in cellular reproduction and DNA organization, as they mediate the cleavage of single and double stranded DNA to relax supercoils, untangle catenanes, and condense chromosomes in eukaryotic cells. Topoisomerase inhibitors influence these essential cellular processes. Some topoisomerase inhibitors prevent topoisomerases from performing DNA strand breaks while others, deemed topoisomerase poisons, associate with topoisomerase-DNA complexes and prevent the re-ligation step of the topoisomerase mechanism. These topoisomerase-DNA-inhibitor complexes are cytotoxic agents, as the un-repaired single- and double stranded DNA breaks they cause can lead to apoptosis and cell death. Because of this ability to induce apoptosis, topoisomerase inhibitors have gained interest as therapeutics against infectious and cancerous cells.
A depside is a type of polyphenolic compound composed of two or more monocyclic aromatic units linked by an ester group. Depsides are most often found in lichens, but have also been isolated from higher plants, including species of the Ericaceae, Lamiaceae, Papaveraceae and Myrtaceae.
Cetrelia is a genus of leafy lichens in the large family Parmeliaceae. They are commonly known as sea-storm lichens, alluding to the wavy appearance of their lobes. The name of the genus, circumscribed in 1968 by the husband and wife lichenologists William and Chicita Culberson, alludes to the former placement of these species in the genera Cetraria and Parmelia.
Xanthoparmelia is a genus of foliose lichens in the family Parmeliaceae. This genus of lichen is commonly found in the United States, as well as Australia, New Zealand and Ecuador.
Olivetol, also known as 5-pentylresorcinol or 5-pentyl-1,3-benzenediol, is an organic compound found in certain species of lichen; it is also a precursor in various syntheses of tetrahydrocannabinol.
Parmotrema perlatum, commonly known as the powdered ruffle lichen, is a common species of foliose lichen in the family Parmeliaceae. The species has a cosmopolitan distribution and occurs throughout the Northern and Southern Hemispheres. Parmotrema perlatum is a prominent and widely recognised species within its genus across primarily temperate zones, preferring humid, oceanic-suboceanic habitats. It is found in diverse geographic areas including Africa, North and South America, Asia, Australasia, Europe, and islands in the Atlantic and Pacific oceans. It usually grows on bark, but occasionally occurs on siliceous rocks, often among mosses.
In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to ecological pressures such as pathogen and insect attack, UV radiation and wounding. As they are present in food consumed in human diets and in plants used in traditional medicine of several cultures, their role in human health and disease is a subject of research. Some phenols are germicidal and are used in formulating disinfectants.
A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical reagent on different parts of the lichen and noting the colour change associated with application of the chemical. The tests are routinely encountered in dichotomous keys for lichen species, and they take advantage of the wide array of lichen products produced by lichens and their uniqueness among taxa. As such, spot tests reveal the presence or absence of chemicals in various parts of a lichen. They were first proposed as a method to help identify species by the Finnish lichenologist William Nylander in 1866.
Remototrachyna is a genus of foliose lichens in the large family Parmeliaceae. It was separated from the genus Hypotrachyna based on the structure of the excipulum and genetic differences.
Isolichenan, also known as isolichenin, is a cold-water-soluble α-glucan occurring in certain species of lichens. This lichen product was first isolated as a component of an extract of Iceland moss in 1813, along with lichenin. After further analysis and characterization of the individual components of the extract, isolichenan was named in 1881. It is the first α-glucan to be described from lichens. The presence of isolichenan in the cell walls is a defining characteristic in several genera of the lichen family Parmeliaceae. Although most prevalent in that family, it has also been isolated from members of the families Ramalinaceae, Stereocaulaceae, Roccellaceae, and Cladoniaceae. Experimental studies have shown that isolichenan is produced only when the two lichen components – fungus and alga – are growing together, not when grown separately. The biological function of isolichenan in the lichen thallus is unknown.
Olivetolic acid is an organic compound that is an intermediate in the biosynthetic pathway of the cannabinoids in Cannabis sativa.
Cetrelia sayanensis is a species of foliose lichen in the family Parmeliaceae. Found in Europe, it was formally described as a new species in 2009 by lichenologists Tatyana Otnyukova, Nikolay Stepanov, and John Alan Elix. The type was collected along the Kulumys ridge on the West Sayan Mountains of southern Siberia. Here it was found growing on the bark of an old stem of Sorbus sibirica, at an altitude of 800 m (2,600 ft). It has also been collected in several neighbouring areas, all at altitudes between 400–930 m (1,310–3,050 ft), with the bark of Abies, Betula, Salix, and Sorbus as the typical substrates. In 2019, the lichen was recorded from Austria, its first reported occurrence in middle Europe.
Salazinic acid is a depsidone with a lactone ring. It is found in some lichens, and is especially prevalent in Parmotrema and Bulbothrix, where its presence or absence is often used to help classify species in those genera.
Lichexanthone is an organic compound in the structural class of chemicals known as xanthones. Lichexanthone was first isolated and identified by Japanese chemists from a species of leafy lichen in the 1940s. The compound is known to occur in many lichens, and it is important in the taxonomy of species in several genera, such as Pertusaria and Pyxine. More than a dozen lichen species have a variation of the word lichexanthone incorporated as part of their binomial name. The presence of lichexanthone in lichens causes them to fluoresce a greenish-yellow colour under long-wavelength UV light; this feature is used to help identify some species. Lichexanthone is also found in several plants, and some species of fungi that do not form lichens.
Barbatic acid is an organic compound that is made by some lichens. It is in the structural class known as depsides. It is particularly common in the genera Usnea and Cladonia.
Platismatia glauca is a common and widespread species of corticolous (bark-dwelling), foliose lichen in the family Parmeliaceae.
Confluentic acid is an organic compound belonging to the chemical class known as depsides. It serves as a secondary metabolite in certain lichens and plays a role in distinguishing closely related species within the genus Porpidia. In 1899, Friedrich Wilhelm Zopf isolated a compound from Lecidea confluens, which he initially named confluentin and noted for its melting point of 147–148 °C. This substance demonstrated the ability to turn litmus paper red and, when interacting with alkali, decomposed into carbon dioxide and phenol-like compounds. Zopf subsequently revised the chemical formula and melting point of the compound. Siegfried Huneck renamed it confluentinic acid in 1962, characterising it as optically inactive, with distinct colour reactions and solubility properties, and determined its molecular formula as C28H36O8.
