Functional properties include: antimicrobial, insecticidal, pharmacological, physiological and miscellaneous.
10.5.1 Pharmacological effects
Many Pelargonium species have been used in the past as traditional medicines in Southern
Africa with mainly anti-dysenteric properties (Watt and Breyer-Brandwijk, 1962), e.g. root of P. transvaalense and P. triste and the leaves of P. bowkeri and P. sidaefolium. Some Pelargonium species were also used to treat specific maladies, e.g. P. cucullatum for nephritis; P. tragacanthoides for neuralgia, P. luridum and P. transvaalense root for fever; P. minimum, P. reniform and P. grossularioides for menstrual flow (Pappe 1868; Watt and Breyer-Brandwijk, 1962). The latter was also used as an emmenagogue and abortifacient by both Zulus and Boers and has recently been studied further (Lis-Balchin and Hart, 1994) and shown to have spasmogenic properties on the uterus and smooth muscle preparations in vitro. Pelargonium reniforme and P. sidoides extracts are currently used in the herbal remedy Umckaloabo® (produced in Germany) for respiratory ailments, owing to its strong antimicrobial properties; it also has immunomodulatory properties, leishmanicidal activity and interferon-like properties (Kolodziej, 2002).
Imaseki and Kitabatake (1962) found an antispasmodic action of citronellol, geraniol and linalool on mouse small intestine, but Pelargonium EOs were not studied until recently. Results from experiments on isolated guinea pig ileum demonstrate that the majority of Pelargonium oils, and their components, produce a relaxation of smooth muscle through a mechanism involving adenylate cyclase and a rise in the concentration of the second messenger, cAMP (Lis-Balchin and Hart, 1997, 1998; Hart and Lis-Balchin, 2002); there is some evidence of calcium channel blockade, but only at concentrations higher than those required to produce a significant spasmolytic effect, in contrast to other essential oils (Hills and Aaronson, 1991). Preliminary results using more hydrophilic (methanolic) extracts of Pelargonium species and cultivars, and their teas, indicate that most have a contractile effect initially, which is followed by a relaxation (Hart and Lis-Balchin, 2002). There is also some evidence that a few methanolic extracts use calcium channels at normal concentrations.
The essential oils of P. grossularioides, as well as its water-soluble and methanolic extracts, were all spasmogenic on guinea pig ileum and on the rat uterus, in contrast to all other geranium oils and their components, such as geraniol and linalool and all other commercial oils studied, which had a spasmolytic action on the uterus. Action on skeletal muscle (chick biventer and rat phrenic nerve diaphragm) showed an increase in tone and reduction of contraction. Alkaloid extracts obtained from the zonals (Lis-Balchin, 1996,1997; Lis-Balchin et al., 1996b) were also all spasmolytic on guinea pig ileum; as were methanolic, water-soluble extracts (teas), and alkaloid fractions of P. luridum (root) and the leaves of P. inquinans and Pelargonium cultivars.
The antimicrobial action of geranium oil was reviewed recently by Deans (2002). Deans and Ritchie (1987) studied 50 commercial volatile oils at four concentrations against a range of 25 bacterial genera: 'geranium oil' was most effective against the dairy products organism Brevibacterium linens and the toxin-producing Yersinia enterocolitica but, in contrast with Klebsiella pneumoniae and Escherichia coli, its presence resulted in enhancement of growth. Pattnaik et al. (1995) tested geranium oil for antibacterial activity against 22 bacteria (Gram-positive cocci and rods, Gram-negative rods) and 12 fungi (3 yeast-like, 9 filamentous) by disc diffusion. Only 12 bacterial strains were inhibited by the geranium oil, but all the fungi were inhibited. Lis-Balchin et al. (1996c) found that antibacterial activity against 25 different bacteria varied among samples of commercial oil, ranging from 8 to 19 inhibited, which could not be correlated with the chemical composition of the samples. The action of the geranium oils against 20 strains of Listeria monocytogenes was again very variable, the number of strains affected ranging from 3 to 16 out of 20 (Lis-Balchin and
Deans, 1997a); in antifungal studies, the geranium samples showed from 0 to 94% inhibition of Aspergillus niger, 12 to 95% against A. ochraceus and 40 to 86% against Fusarium culmorum, in agreement with the results of an earlier study (Lis-Balchin et al., 1995) wherein 24 cultivars were tested for antimicrobial activity against 25 test bacteria and A.
In a study into the potential usage of mixtures of plant volatile oils as synergistic antibacterial agents in foods, Lis-Balchin and Deans (1997b) included 'geranium oil' in a mixture with nutmeg and bergamot oils, but no synergistic effect was found (similarly with other combinations). The antimicrobial activity of Pelargonium oil components (Dorman and Deans, 2000) showed the following ranking order of activity: linalool > geranyl acetate > nerol > geraniol > menthone > ß-pinene > limonene > a-pinene. Compared with more phenolic compounds, these activities are relatively modest. The bacteria showing the greatest level of inhibition were Clostridium sporogenes > Lactobacillus plantarum > Citrobacter freundii > Escherichia coli > Flavobacterium suaveolens.
Pelargonium x hortorum leaves (unscented) were reported as being most active against Candida albicans, Trichophyton rubrum and Streptococcus mutans, organisms causing common dermal, mucosal or oral infections in humans (Heisey and Gorham, 1992). Pelargonium species, including the commercial 'Geranium oil' have been shown to have antioxidative properties (Dorman et al., 2000; Fukaya et al., 1988; Youdim et al., 1999), though these properties had very variable activities in different commercial samples of 'Geranium oil' (Lis-Balchin et al., 1996a).
There is little direct scientific evidence for the physiological effectiveness of geranium oil apart from the pharmacological studies and studies in the brain (Torii et al., 1988; Manley, 1993). There are miscellaneous physiological reactions attributed to a geranium component, linalool: a hypoglycaemic effect in normal and streptozotocin-diabetic rats (Afifi et al., 1998); a hepatic peroxysomal and microsomal enzyme induction in rats (Roffey et al., 1990), as does geraniol (Chadba and Madyastha, 1984) and choleretic and cholagogic activity of a mixture of linalool and a-terpinol (Peana et al., 1994; Gruncharov, 1973). Linalool's dose-dependent, sedative effect on the central nervous system of rats could be caused by its inhibitory activity on glutamate binding in the cortex (Elisabetsky et al., 1995a,b).
Geranium oil is commonly used in aromatherapy, owing to the misinterpretation of aromatherapists of old English herbals (Culpeper 1653), which referred to the real Geranium genus (e.g. G. robertianum) and not Pelargonium. The actual usages of the Geranium extracts mentioned in old herbals are mainly (antidiarrhoeal) associated with their tannin content and other water-soluble chemicals, e.g. flavonoids, in the leaves. Essential oils, on the other hand, are steam-distilled volatiles and do not contain these components. Valnet (1982) gave geranium oil's major attributes as 'its vulnerary powers and its power to mend fractures and eliminate cancers' taken straight out of the old herbals; his directions for oral use are given as for 'Herb Robert', a real Geranium (Lis-Balchin, 2002d)! The mistake was then perpetuated. No evidence has been provided by clinical studies, e.g. in childbirth (Burns and Blaney, 1994), for the current usage of geranium oil, while there is pharmacological evidence for the decrease and even cessation of uterine contractions in animal experiments, which could prove harmful (Hart and Lis-Balchin, 2002). Other clinical studies (using mainly lavender oil) have not shown any extra benefit of using essential oils with massage, as massage in itself provides a beneficial effect, e.g. Dunn et al. (1995). Essential oil inclusion may have a detrimental effect due to sensitization (Schaller and Korting, 1995; Anderson et al., 2000). Furthermore, although 'geranium' oils are very active on many different animal tissues in vitro (Lis-Balchin et al., 1997), there is no proof as yet whether minute amounts (as used in aromatherapy massage) can have direct action on target organs or tissues rather than through the odour pathway (Vickers, 1996), despite some evidence that certain essential oil components can be absorbed either through the skin or lungs (Jager et al., 1992; Buchbauer et al., 1993).
10.5.5 Psychological and physiological effects of geranium oil
The main action of essential oils is probably on the primitive, unconscious, limbic system of the brain, which is not under the control of the cerebrum or higher centres (Kirk-Smith, 2002). Many fragrances have been shown to have an effect on mood and in general, pleasant odours generate happy memories, more positive feelings and a general sense of well-being (Warren and Warrenburg, 1993). Some essential oils have also been used in hospitals and hospices to create a more happy and positive atmosphere and also in offices and factories to enhance productivity. Many essential oil vapours have been shown to depress contingent negative variation (CNV) brain waves in human volunteers (i.e. sedative); others increase CNV (i.e. stimulant): these parameters were often in agreement with the effect on mouse motility and the direct effect of the essential oil on smooth muscle in vitro. However, geranium oil has both a sedative and stimulant effect on the CNV (Lis-Balchin, 2002d).
Geranium oil Bourbon, Algerian, Moroccan were granted GRAS (generally recognized as safe) status by FEMA (1965) and approved by the US Food and Drug Administration (FDA) for food use. The Council of Europe included geranium oil in the list of spices, seasonings, etc. deemed admissible for use with a possible limitation of the active principle in the final product.
10.5.7 Biological toxicity studies
Acute toxicity: oral LD50 in rats > 5 g/kg); dermal in rabbits, 2.5 g/kg (Moreno, 1973).
Irritation: applied undiluted to abraded or intact rabbit skin for 24 h under occlusion was found to be moderately irritant (Moreno, 1973), but applied to backs of hair-less mice, it was not irritating (Urbach and Forbes, 1972). Human patch test (closed) to 10% geranium oil in petrolatum produced no irritation after 48 h (RIFM, 1974).
Sensitization: a maximization test on 25 volunteers, using 10% in petrolatum produced no sensitization (RIFM, 1974).
Phototoxicity has not been found for geranium oil.
There are very few, scattered, references to any toxicity, and all references are to contact dermatitis and sensitization. Most of the references are to the geranium oil and the main components geraniol (Lovell, 1993). Pelargonium plants themselves have caused hand dermatitis (Anderson, 1923) and sensitization (Rook, 1961; Hjorth, 1969).
Patch tests to geraniol proved negative but dermatitis to perfumes containing geranium oil has been shown in a few cases (Klarmann, 1958). Ointments containing geraniol, e.g. 'Blastoestimulina', were reported to cause sensitization when used in the treatment of chronic leg ulcers (Romaguera et al., 1986; Guerra et al., 1987), although the patients were also sensitive to other ointments that contained no essential oils.
Sensitization to geraniol using a maximization test proved negative (Opdyke1975), but the allergen may be geraniol as cross-reactions often occurred with citronella (Keil, 1947); however, the main sensitizer in citronella is citronellal, with citronallol less reactive; geraniol was even weaker, as was citral. In two cases, strong reactions were obtained with 1% solutions of citronellal and weaker ones with citronellol, geraniol, geranyl acetate. In 23 out of 23 cases no response was found using lemon oil, suggesting specificity of the response. In a lemon oil sensitization case, a-pinene gave a greater response than P-pinene: this is because of the close similarity between limonene and a-pinene (due to an exposed methylene radical).
Recent Japanese studies, on patients with ordinary cosmetic dermatitis and pigmented cosmetic dermatitis, who showed a positive allergic responses to a wide range of fragrances (Nakayama, 1998), gave rise to a list of common cosmetic sensitizers and primary sensitizers, which included geranium oil, geraniol, sandalwood oil, artificial sandalwood, musk ambrette, jasmine absolute, hydroxycitronellal, ylang ylang oil, cinnamic alcohol, cinnamaldehyde, eugenol, balsam of Peru and lavender oil. Geraniol was found to give a positive patch test in over 1.2% cases when used at 1% in white petrolatum with 5% sorbitan sesquioleate (Frosch, 1998). D-Limonene, although present in small quantities in geranium oil has shown many sensitization reactions.
The European Council and the European Commission have now issued the 7th Amendment to their Cosmetic Directive, 2002, and have included geraniol, limonene and citronellol in its list of sensitizers (see Table 10.1).
Was this article helpful?
This eBook explains how Aromatherapy has something to do with scents and smells treating illnesses and conditions. Many people who do not like the sometimes-unpleasant side effects of prescribed medication, particularly for depression, stress, or other similar disorders, have opted to use aromatherapy to help reach the desired state of being.