Plant compounds, menthol

These observations throw light on the mechanism which governs the transformation in the plant of the compounds belonging to the menthol group. This alcohol being produced simultaneously with the green parts of the plant, is partially esterified in the leaves the esterification here... 

Isoprene metabolism in plants is very complex. Plants can synthesize many types of aromatic substances and volatile oils from isoprenoids. Examples include menthol (1= 2 ), camphor (1 = 2), and citronellal (1 = 2). These Cio compounds are also called monoterpenes. Similarly, compounds consisting of three isoprene units (1 = 3) are termed sesquiterpenes, and the steroids (1 = 6) are called triterpenes. 

Monoterpenes, 10-carbon-containing terpenoids, are composed of two isoprene units, and found abundantly in plants, e.g. (+)-limonene from lemon oil, and (—)-linalool from rose oil. Many monoterpenes are the constituents of plant volatile oils or essential oils. These compounds are particularly important as flavouring agents in pharmaceutical, confectionery and perfume products. However, a number of monoterpenes show various types of bioactivity and are used in medicinal preparations. For example, camphor is used in liniments against rheumatic pain, menthol is used in ointments and liniments as a remedy against itching, bitter-orange peel is used as an aromatic bitter tonic and as a remedy for poor appetite and thymol and carvacrol are used in bactericidal preparations. 

The organic compounds available to us today are those present in living things and those formed over millions of years from dead things. In earlier times, the organic compounds known from nature were those in the essential oils that could be distilled from plants and the alkaloids that could be extracted from crushed plants with acid. Menthol is a famous example of a flavouring compound from the essential oil of spearmint and ds-ja.smone an example of a perfume distilled from jasmine flowers. 

Terpenes have a wide variety of structures. They can be acyclic or have one or more rings. They may have only carbon and hydrogen atoms, or they may have heteroatoms as well. The most common heteroatom in terpenes is oxygen. Many essential oils, a group of compounds isolated from plant sources by distillation, are terpenes. Examples include myrcene and menthol. 

Terpenes are are a class of compounds whose chemical structures are based on a number of isoprene units , derived from the hydrocarbon CH2=C(CH3)-CH=CH2 they may themselves be hydrocarbons, but may also contain alcohol (OH), aldehyde/ketone (CO) and carboxylic acid (COOH) groups. Monoterpenes are Cm compounds derived from two isoprene units, sesquiterpenes (Cu) are derived from three isoprene units, diterpenes (C20) from four and tritepenes (C30) from six. Terpenes are widespread in plants, where they are largely responsible for the odor, and they are the major constituents of plant-derived essential oUs . Among the best known terpenes are 3-pinene (turpentine), camphor, menthol and citroneUal (aU monoterpenes) and farnesol (a sesquiterpene that is a constituent of the essential oils of many plants). Certain terpenes have important biological roles vitamin A, for example, is a diterpene, and steroid hormones have a structure related to triterpenes (and are biosynthesized by a similar route). 

Menthol is a white, waxy crystalline compound having a strong odor of peppermint. Its main source is oil of peppermint from the plant, Mentha arvensis. It is an ingredient of decongestant ointments and nasal sprays and is also used to flavour toothpaste and cigarettes. 

Abstract — (-)-Isopiperitenone (1) is a normal biosynthetic intermediate in menthol biosynthesis of M. piperita. It was hoped that feeding of this intermediate could enhance biosynthesis of memhol in the suspension cell culture of the plant. When this compound was fed to the suspension culture, it was converted to menthol as expected albeit in a lower extent. However, its major metabolites were unexpected oxygenated products, (-)-7-hydrDxy-isopiperitenone (2), and (+)-(4 6S)-6-hydroxyisopiperitenone (3 and 4), (+)-... 

A case report indicated a positive patch test result to chick-weed in a patient allergic to a number of common weeds. Analysis of the plant material used for the testing indicated the presence of borneol, menthol, linalool, and 1,8-cineole, all compounds that are not known to be present in chick-weed, bringing into doubt the identity of the material tested (Jovanovi et al. 2003). 

Two German chemists, Heinrich Otto Wieland (1877-1957) and Adolf Windaus (1876- ), worked out the structure of steroids and related compounds. (Among the steroids are a number of important hormones.) Another German chemist, Otto Wallach (1847-1931), painstakingly elucidated the structure of terpenes, important plant oils (of which menthol is a well-known example), while still another, Hans Fischer (1881-1945), established the structure of heme, the coloring matter of blood. 

The compounds menthone and menthol are fragrant substances present in an oil produced by mint plants ... 

Monoterpenes are important constituents of essential oils. These complex mixtures of compounds, as well as individual monoterpenes are used in medicine (F 2) and industry (F 4). Commercially important monoterpenes are, for instance, menthol, camphor, carvone, thymol, fenchone, and oc-pinene. Monoterpenes flavor foodstuffs and beverages (F 1). Citral, for example, is an important constituent of the smell of lemon. Thymol is involved in the flavor of mandarin oranges. Other monoterpenes, e.g., limonene and geraniol, are constituents of flower scents and attract plant pollinators (E 5.5.1). High monoterpene concentrations in plants will repel most potential predators, but my attract some animals (E 5.5.3). Animals use citronellal, citral, and oc- and jS-pinene als feeding deterrents (E 5.1) and geraniol, geranyl esters, myrcene, and terpinolene as pheromones (E 4). Some monoterpenes, e.g., 1,8-cineole and camphor, are also involved in plant-plant interactions (E 5.3). 

Menthol is a natural compound isolated from a variety of plants and it has been mostly used as analgesic. Recently, it was demonstrated by a number of studies that menthol produces cool sensation which is mediated by the activation of TRPM8 channels. Experimental work from different laboratories has demonstrated that menthol has several additional pharmacological activities that compose its pharmacological features. In this chapter, we have pointed out a scenario where menthol is posed as the main actor toward the understanding of its biological and toxicological effects. 

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