Iridoid valepotriates

N.A. Galium aparine L. Iridoid valepotriates, polyphenolic acids, anthraquinones, tannins.99107 For vitamin C deficiency. 

Valerian is used in the treatment of insomnia and stress and anxiety. The important active compounds of valerian are the valepotriates (iridoid molecules) and valeric acid. These compounds are found exclusively in valerian. Originally, it was thought that just the valepotriates were responsible for valerian s sedative effects but, recently, an aqueous extract of valerian has also been shown to have a sedative effect. As the valepotriates are not soluble in water, it was concluded that valeric acid also possesses sedative action and is the chemical factor responsible for the sedative effect noted in human clinical trials with aqueous extracts of valerian (Murray, 1995). Valerian inhibits the uptake of GABA and enhances the release of GABA. 

Note Valerian consists of the dried rhizome and roots of Valeriana officinalis Linne (Fam. Valerianaceae). It has been employed as an antianxiety agent and sleep aid for more than 1000 years. The drug contains from 0.3 to 0.7% of an unpleasant-smelling volatile oil containing bornyl acetate and the sesquiterpenoids, valerenic acid, and acetoxyvalerenolic acid. Also present is a mixture of lipophilic iridoid principles known as valepotriates. These bicyclic monoterpenoids are quite unstable and occur only in the fresh plant or in material dried at temperatures under 40°C. Although the specific active principals of valerian have not been determined, it is possible that a combination of the sesquiterpenoids and the valepotriates may be involved. The drug may be administered as a tea prepared from 2 to 3 g of the dried herb or equivalent amounts of a tincture or extract may be employed. 

The structure for valerosidate is incorrect in the previous Report (Vol. 5, p. 17). A new valepotriate has been isolated from Valeriana officinalis and shown spectroscopically to be 7-epideacetylisovaltrate (103) 193 it is also shown to be related to didrovaltrate (104) stereochemically, but in view of the recently reported absolute configuration of didrovaltrate (104)192 this assignment must be questioned. The occurrence of iridoids in the Argentine ant Iridomyrmex humilis has been re-investigated.194... 

The CNS-depressant component of valerian is still unknown. Thus far, three major constituents of valerian have been identified the volatile or essential oil, containing sesquiterpenes and monoterpenes, nonglycosidic iridoid esters (valepotriates), and a small number of alkaloids (2). Valepotriates are unstable compounds and are easily hydrolyzed by heat and moisture (22). In addition, valepotriates are not water soluble, and aqueous extracts contain... 

The CNS depressant component of valerian is still unknown. Thus far, three major constituents of valerian have been identified the volatile or essential oil, containing sesquiterpenes and monoterpenes, nonglycosidic iridoid esters (valepotriates), and a small number of alkaloids (Anonymous, 1991). Valepotriates are unstable compounds and are easily hydrolyzed by heat and moisture (Wagner et al., 1998). In addition, valepotriates are not water soluble, and aqueous extracts contain small amounts (Wagner et al., 1998). For example, the aqueous extract used in the study by Balderer and Borbely, described previously, was analyzed using thin-layer chromatography (TLC), and no valepotriates were detectable. Furthermore, valepotriates are not well absorbed orally (Tyler, 1993). Therefore, the likelihood that valepotriates are a major contributor to valerian s effects is questionable. Because of the low amount of alkaloid present in preparations, their contribution is also questionable (Houghton,... 

Generally iridoids are divided in two categories, iridoids and secoiridoids and these mostly exist as glycosides. Iridoids are also found in aldehydes, alcohols (iridodial (1) iridodiol (2)), alcoholic esters (valepotriates), lactones (irridomyrmecin (3), nepetalactone (4)) and alkaloids (actinidine (5), skytanthine (6)) forms. Secoiridoids on the other hand are formed by cleavage of cyclopentane ring of iridoid. 

Most plant iridoids are bitter substances. They may repel predators, but attract certain specialized animals (E 5.5.3). Some are used in the production of liquors (F 1) and in medicine (F 2). Nonglycosylated iridoids, e.g., iridodial and doli-chodial, are constituents of the defense secretions of ants (E 5.1). Iridoid epoxides, the valepotriates, e.g., valtrate, are sedative components of Valeriana officinalis (F2). 

The bitter iridoid monoterpenes usually occur as glycosides (see Chapter 4). Non-glycosidic iridoids include the sedative valepotriates found in valerian—Valeriana spp. (Valerianaceae). They are closely related to nepetalactone, the volatile component of essential oil of catnip, Nepeta cataria (Lamiaceae), responsible for attracting cats to the plant. 

Another group of iridoids, the valepotriates ocurring in the Valerianaceae exhibited an inhibitory activity on the alternative pathway of the complement system in a dose-dependent manner [35]. 

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