Usnic acid is a naturally occurring dibenzofuran derivative found in several lichen species with the formula C18H16O7. It was first isolated by German scientist W. Knop in 1844 and first synthesized between 1933 and 1937 by Curd and Robertson. Usnic acid was identified in many genera of lichens including Usnea, Cladonia, Hypotrachyna, Lecanora, Ramalina, Evernia, Parmelia and Alectoria. Although it is generally believed that usnic acid is exclusively restricted to lichens, in a few unconfirmed isolated cases the compound was found in kombucha tea and non-lichenized ascomycetes.
The Chichibabin pyridine synthesis is a method for synthesizing pyridine rings. The reaction involves the condensation reaction of aldehydes, ketones, α,β-Unsaturated carbonyl compounds, or any combination of the above, with ammonia. It was reported by Aleksei Chichibabin in 1924. Methyl-substituted pyridines, which show widespread uses among multiple fields of applied chemistry, are prepared by this methodology.
Pseudevernia is a genus of foliose lichens in the family Parmeliaceae. The type species of the genus, Pseudevernia furfuracea, has substantial commercial value in the perfume industry.
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.
FriedrichWilhelm Zopf was a well-known German botanist and mycologist. He dedicated to his whole life with fungal biology, particularly in classification of fungi and dye production in fungi and lichens. Besides, his textbook on fungi called “Die pilze in morphologischer, physiologischer, biologischer und systematischer beziehung ” in 1890 was also an outstanding work on the subject for many decades. The unicellular achlorophic microalgae Prototheca zopfii is named after him because of his profound suggestions and contributions to Krüger's pioneering work in Prototheca. Thus, his numerous contributions gave him a special status in mycological history.
Cerevisterol (5α-ergosta-7,22-diene-3β,5,6β-triol) is a sterol. Originally described in the 1930s from the yeast Saccharomyces cerevisiae, it has since been found in several other fungi and, recently, in deep water coral. Cerevisterol has some in vitro bioactive properties, including cytotoxicity to some mammalian cell lines.
Secalonic acids are a group of xanthone derivatives closely related to ergoflavin and ergochrysin A that are collectively called ergochromes and belong to a class of mycotoxins initially isolated as major ergot pigments from the fungi Claviceps purpurea that grows parasitically on rye grasses. From early times and particularly in medieval Europe the consumption of grains containing ergot has repeatedly lead to mass poisonings known as ergotism which was caused by toxic ergot alkaloids and mycotoxins such as the ergochromes, due to contamination of flour by C. purpurea. A cluster of genes responsible for the synthesis of secalonic acids in C. purpurea has been identified. Secalonic acid D the enantiomer of secalonic acid A is a major environmental toxin, isolated from the fungus Penicillium oxalicum, and is a major microbial contaminant of freshly-harvested corn which causes toxicity through contamination of foodstuffs.
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.
Jack Rodney Laundon was a British lichenologist and became President of the British Lichen Society.
In chemistry, a transition metal chloride complex is a coordination complex that consists of a transition metal coordinated to one or more chloride ligand. The class of complexes is extensive.
Merochlorophaeic acid is a depside with the molecular formula C24H30O8 which has been isolated from the lichen Cladonia merochlorophaea.
Anziaic acid is a depside found in lichens. It gives a red reaction in the C test. The two phenolic rings have a pentyl side chain. It is an ester dimer of olivetolic acid.
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.
Thamnolic acid is a β-orcinol depside with the molecular formula C19H16O11. Thamnolic acid was first isolated from the lichen Thamnolia vermicularis, but it also occur in Cladonia species.
Lichen products, also known as lichen substances, are organic compounds produced by a lichen. Specifically, they are secondary metabolites. Lichen products are represented in several different chemical classes, including terpenoids, orcinol derivatives, chromones, xanthones, depsides, and depsidones. Over 800 lichen products of known chemical structure have been reported in the scientific literature, and most of these compounds are exclusively found in lichens. Examples of lichen products include usnic acid, atranorin, lichexanthone, salazinic acid, and isolichenan, an α-glucan. Many lichen products have biological activity, and research into these effects is ongoing.
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.
Cladonia rei, commonly known as the wand lichen, is a species of ground-dwelling, fruticose lichen in the family Cladoniaceae. It is a widely distributed species, having been reported from Africa, Asia, Australasia, Europe, and North America. It is identified by its slightly dirty-colored, rough-surfaced, slender podetia that grow up to 9 cm (3.5 in) tall. Diagnostic characters of the lichen include the continuously sorediate, green-and-brown-mottled, podetia that taper upward to a point, while chemically, it contains homosekikaic and sekikaic acids. Its reduced capacity to bioaccumulate toxic heavy metals from its surroundings, as well as its ability to switch photobiont partners, allows the lichen to colonize and survive highly polluted habitats. There are several other Cladonia species that are somewhat similar in appearance, but can be distinguished either by subtle differences in morphology, or by the secondary chemicals they contain.
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.
Placidiopsis hypothallina is a species of saxicolous (rock-dwelling) crustose lichen in the family Verrucariaceae, described as a new species in 2002. It is unique within its genus for its thallus primarily composed of a hyphal hypothallus resembling a subiculum found in some non-lichenised ascomycetes. It is found in Brazil and Taiwan.
