Iridoids biological activities

Iridoids have shown a broad range of biological activities, such as an antibacterial, antifungal, anti-inflammatory, antitumoral, hepatoprotective, cardioprotective, antioxidative, antiprotozoal and anti-insect properties [13,14,15,16,17,18,19]. In vitro activities inhibiting the hepatitis C virus, the differentiation of the adipocyte, and PPARa activation activities have been also described [20, 21]. 

Some volatile iridoid monoterpenes with biological activity are also found in essential oils and in insect pheromonal and defensive substances. Eisner ( ) found that 17 species of insects were repelled by the iridoid monoterpene nepetalactone. Lacewings (Chrysopa septempunctata) are attracted by the leaves and fruits of Actinidia polyqama (Actinidiaceae) which contain a series of volatile iridoid monoterpenes (67). 

Several non-volatile iridoid monoterpenes occur as glycosides and have been observed to have biological activity. For example, xylomolin, from the unripe fruits of Xylocarpus moluccensis Roem. (Meliaceae) has antifeedant activity against Spodoptera exempta an African armyworm at 100 ppm ( ) and crotepoxide from Croton macrostachys (Euphorbiaceae) possesses antifeedant activity against Spodoptera exempta (85). 

ABSTRACTS The iridoid and secoiridoid derivatives of Oleaceae have been grouped regarding structural similarities. The biosynthetic routes leading to these compounds and their most relevant biological activities, described up to now, have also been reviewed. 

In this work, we want to keep the structures of the iridoids and secoiridoids which are present in Oleaceae, their biosynthesis and the biological activities, so far described, up to date. 

Terpenes.- The first total synthesis of the biologically active marine natural product metachromin A (241) has been achieved using an ( )-stereoselective olefination with the phosphonate (240) as the key step. The olefination reaction of the a-cyanophosphonate (242) with ( , )-farnesal (243) has been studied under a wide variety of conditions with a view to optimising (Z)-stereoselectivity.Excellent (Z)-stereoselectivity was achieved and the resulting procedure applied to a stereoselective synthesis of plaunotol (244). Epimerisation and P-elimination of base-sensitive substrates can cause problems in phosphonate- and phosphine oxide-based olefinations. Such reactions have been excluded in a recent report of enantiospecific syntheses of iridoid monoterpene lactones by intramolecular phosphonate-olefination through the use of mild bases such as DBU and di(wopropyl)ethyl amine/lithium chloride. 

Formation of Deoxyloganic Acid from Geraniol Formation of 8-e/ i-Deoxyloganin and Related Iridoids Iridoids Derived from 10-Hydroxycitronellol Conversion of Loganin to Secologanin Secologanin as a Precursor for Indole Alkaloids Distribution of Iridoid Monoterpenes Biological Activity... 

Many iridoid monoterpenes possess biological activity, although the role of these compounds in biological interactions has not been studied as much as many or other groups of secondary metabolites. 

Stermitz, F. R., Iridoid glycosides and aglycones as chiral syn-thons, bioactive compounds, and lepidopteran defenses, in Biologically Active Natural Products Potential Use in Agriculture (H. G. Cutler, ed.), ACS Symposium Series 380, 397-402, American Chemical Society, Washington, DC, 1988. 

The diversity of biological activity exhibited by several iridoids has generated much interest for their synthesis. Due to difficulties of glycosidation of iridoid aglycones, only a few synthetic approaches in this area have been reported. Some of these synthetic routes for stereoselective synthesis of natural iridoids are discussed here briefly to make it inspiring among the synthetic chemists for their future plans. 

Chang IM, Hur SO, Lee ES 1985 Biological activities of iridoid glycosides I. Antimicrobial activities and inhibition of RNA and protein synthesis. Abstr Internat Res Cong Nat Prod. Coll Pharm, Univ N Carolina, Chapel Hill NC. p. ABSTR-192... 

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. 

Tundis R, Loizzo MR, Menichini F, Statti GA, Menichini F. Biological and Pharmacological Activities of Iridoids Recent Developments. Mini-Reviews in Medicinal Chemistry 2008 8 399-420. 

Iridoids and secoiridoids show a wide variety of biological and pharmacological activities which have been reviewed by Ghisalbert [6] up to 1998. We report here a review of the most relevant compounds of this type isolated from Oleaceae. 

Ghisalberti, E.L. (1998) Biological and pharmacological activity of naturally occurring iridoids and secoiridoids. Phytomedicine, 5,147 163. 

---