Iridoids sedative activity

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. 

The relevance of these compounds is in their properties, namely antiinflamatory, muscular relaxing, sedative, antihistaminic hypoglucemical and hypotensive, along with those attributed to iridoids. Therefore, the hydrolysis reaction does not mean the loss of pharmacological activities but it originates a dialdehylde-hemiketal intermediate with much more bioactive strength. The aldehyde may be considered as an amine acceptor in the formation of a Shiff base. 

Iridoids have been isolated from several folk medicinal plants which are used as bitter tonics, sedatives, antipyretic, cough medicine, remedies for arthritis, lumbago and muscular pains, wounds and skin disorders, etc. A good number of research papers on the bioactive iridoids isolated from several folk medicinal plants have been published in the last few decades. We have summarized here only some of the fundamental pharmacological activities of iridoids to create an interest oti the importance of this class of natural products and for their wide applications in the formulations of several prospective herbal drugs. 

Southeast Asia, and about 15 species are distributed in Japan [2], There is a long history of the folk medicinal use of Viburnum species. For example, the dried bark of V. opulus L., which is known as Cramp Bark, is used to alleviate painful menstrual cramps as well as a sedative [3], Native American women took black haw (V. prunifolium L.) to treat the menopause and menstrual cramps [4], The genus Viburnum has been documented to contain a variety of compounds such as iridoids, terpenoids, and aromatic compounds [5,6]. Among the chemical contents of Viburnum species, vibsane-type diterpenoids are considered to be characteristic of the Viburnum species because they have not been fotmd in other higher plants. In this review [7], we focus on the structural diversity, biological activities, and synthesis of vibsane-type diterpenoids, in particular, synthetic studies and neurotrophic activity of neo-vibsanin A and B are emphasized. 

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