Plant secondary metabolites – ubiquitous low molecular weight chemicals
which are not essentials for the host existence and reproduction but serve many
auxiliary functions, are frequently occurring as glycosides, for which particularly
abundant examples exist in antibiotic, saponins and flavonoid categories. Cardiac
glycosides (CG), originally isolated from Digitalis plants, also known as cardiotonic
steroids, have particularly extensive record of ethnopharmacological and medicinal
use. Although their application in treatment of dropsy is documented since 1875,
long time has elapsed before their chemical structure were determined and mechanisms
of their toxicity and cardiotonic action were recognized as inhibition of Na+
/ K+ ATP-ase pump. Contemporary molecular pharmacology has revealed that cardiac
glycosides are endogenous compounds in variety of animals, where they function
as toxins or hormones. Besides, numerous recent studies confirmed anticancer
activity of CGs at very low concentrations. These findings have been possible due to
advances in ultrasensitive analytical techniques and also due to progress in organic
synthesis, particularly total enantioselective syntheses of carbohydrates, which secured
availability of individual CG and their analogs for medicinal chemistry studies