The genera Geranium and Pelargonium are invariably confused by the general public and also plant sales personnel, health food shop workers and alternative medicine practitioners, especially aromatherapists. This confusion has existed before Linnaeus (1753) and his binomial system of classification, where both genera were put under the genus Geranium, and although Sweet (1820) and other botanists reclassified them under two genera, acceptance by the majority of laymen as well as nurserymen is still low. The flowers of typical Geranium and Pelargonium species are shown in Figure 1.1.
Geranium oil is extracted from the leaves of some Pelargonium species and cultivars, but its paramedical effects are often equated with those of the genus Geranium e.g. G. robertianum and G. maculatum. The latter are native to Europe and were used as herbal medicines for hundreds of years; they were written up by Gerard (1633), Culpeper (1652) and even Grieve (1937). The Pelargonium species, native to southern Africa, although introduced to European Botanic Gardens for example in Leiden as early as 1600, was used only as ornamental plants; their medicinal properties were known only to Hottentots, Zulus and the local Boers in South Africa till the early 1900s when there was some mention in the literature. The medicinal properties of the fat-soluble Geranium oil (from Pelargonium) are therefore largely unsubstantiated as
Figure 1.1 Flowers of typical Geranium (a) and Pelargonium (b) species.
they are based solely on the properties attributed to the mainly water-soluble extracts (teas) of Geranium species. A further confusion arises with the Geranium oil derived from G. macrorrhizum in Bulgaria, which is entirely different to the commercial Geranium oil from Pelargonium species in both chemical composition and also medicinal properties etc.
The main usage of Geranium species is in herbal medicine, whilst that of the Pelargonium-derived Geranium oil is in perfumery, cosmetics and aromatherapy products. The production of commercial Geranium oil, from several Pelargonium cultivars, is now mainly in Reunion, Egypt and China; however the true sales of Geranium oil are greatly in excess of that derived from plants, due to the ever-increasing production of synthetic and 'nature-identical' Geranium oil.
Geranium oil contains mainly citronellol and geraniol and their esters, therefore can be easily concocted from cheaper essential oils (EOs) and adjusted to the recommended ISO standards. The antimicrobial activity of such EOs is much greater than that of some authentic oils but has a similar pharmacological effect on smooth muscle (spasmolytic) and the actual odour can be even more appreciated by perfumers than the real EO. It remains to be seen whether aromatherapy has any actual medicinal benefits, other than stress-alleviating, and whether these are attributable only to the true EOs, especially as there is a wide difference in the actual percentage chemical composition of EOs obtained from different geographical sources and also different samples from plants grown in various countries where differences in hybridization has occurred and even the same plants grown under different climatic conditions etc.
The pharmacological activity of the water-soluble extracts of the two genera are not very different: they both have a high proportion of tannins and have an antidiarrhoeal function. The lipophylic EOs of Pelargonium species have mainly a spasmolytic effect on smooth muscle, except for P grossularioides, which was used as an abortifacient in Southern African folk medicine and has been shown to have a spasmogenic action on smooth and uterine muscle.
Pelargonium EOs from leaves of the many different species and cultivars (other than those grown to produce commercial Geranium oil) have very different odours and chemical compositions, but most of the floral-smelling ones act through cyclic AMP (cAMP) as the secondary messenger; others with odours which are more pine or menthol-like have a different mode of action. There is therefore some correlation between their mode of action and their odour and chemical composition. The numerous aromatherapeutic uses for Geranium oil are yet to be scientifically validated, although there is every reason to accept the scientific evidence that inhalation of the aroma and its action through the limbic system has a relaxing effect; theoretically, this could lead to the acceptance that many stress-related conditions like dermatitis, asthma, intestinal problems and headaches could be alleviated.
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