Fascinating metabolic pools of Pelargonium sidoides and Pelargonium reniforme,traditional and phytomedicinal sources of the herbal medicine Umckaloabo®

The metabolic pools of Pelargonium sidoides DC and Pelargonium reniforme CURT, associated with the origin of the herbal medicine Umckaloabo®, exhibit remarkable diversity and complexity. They comprise a variety of phenolic and polyphenolic compounds, a notable wealth of highly oxygenated simple coumarins and a number of miscellaneous uncommon metabolites. Noteworthy, the roots of both species express conspicuously distinct coumarin variations that facilitate their identification. Of the range of coumarins identified the titled species shared the ubiquitous scopoletin and the unique members 6,7,8-trihydroxycoumarin and 8-hydroxy-5,6,7-trimethoxycoumarin merely. Furthermore, the current data on the coumarin profiles suggest the occurrence of coumarin sulphates and coumarin glycosides to be apparently confined to P. sidoides, while the occurrence of conventional proanthocyanidins was a common chemical feature. An unprecedented diterpene, designated as reniformin, was encountered in the roots of P. reniforme, possessing a novel diterpene skeleton linked to a unique p-oxyphenethansulfonic moiety. Coumarins were less abundant in the aerial parts of both species. These were rich in flavonoids and hydrolysable tannins including a unique series of O-galloyl-C-glucosylflavones (P. sidoides and P. reniforme) and novel ellagitannins with a ¹C₄ glucopyranose core in P. reniforme, trivially named pelargoniins, accompanied by the new 4-allyl-2,5-dimethoxyphenol-1-β-d-glucoside. These Pelargoniums have thus represented an attractive source of fascinating secondary metabolites. A proprietary extract of the roots of P. sidoides, EPs^® 7630, has been developed from this traditional herbal medicine and introduced into modern phytotherapy in Europe. Structural examination of EPs^® 7630 constituents showed excellent agreement of the profile with that of P. sidoides.