CHEMICAL AND BIOLOGICAL ASPECTS OF IRIDOID BEARING PLANTS OF TEMPERATE REGION

Naturally occurring iridoids and their glycosides are widely distributed in plants and serve as important taxonomic markers. The iridoids were named after ants of the genus Iridomirmex, from which iridodial, iridomyrmecin, and related compounds were isolated and found to be involved in the defense mechanisms of these insects. Similar structures also exist in plants for example; nepetalactone from Nepeta cataria L. (Lamiaceae), or teucriumlactone C from Teucrium marum L. have marked properties (the effects of the former on cats earned it some evocative names; catnip, Katzenmelisse, herbe-aux-chats). Iridoids are monoterpene compounds characterized by a cyclopenta [c] pyranoid skeleton, also known as the iridane skeleton (cis-2- oxabicyclo-[4, 3, 0]-nonane). These are also found to occur in a variety of animal species. In a broad sense, it is acceptable to include in this group the secoiridoids, which arise from the latter by cleavage of the 7, 8 bond of the cyclopentane ring. This group (of about 500 known structures) chiefly comprises iridoid glycosides (>300), secoiridoid glycosides (>100), and non glycosidic compounds (>100). The group is biosynthetically homogeneous, and is represented by the number of orders and plant families within the dicotyledons. They are elaborated preferentially by gamopetalous plants e.g. Dispsacales, Gentianales, Lamiales, Scrophulariales, which makes them interesting chemotaxonomic markers [1,2]