Geranium thunberghii Sieb et Zucc.
G. thunberghii, known as 'Gen-no-shoko' in Japanese, is used in Kampo (traditional Japanese medicine) particularly as a remedy for diarrhoea induced by inflammation of the small intestine and also for liver and haematological disorders (Kimura et al., 1984). It also has been used to treat cataract (Fukaya etal., 1988). The biological activity is usually ascribed to the tannin content, particularly geraniin. Extracts of the plant have been shown to reduce gastro-intestinal motility in isolated rat intestine (Kan and Taniyama, 1992); have inhibitory effects on cholera toxin-induced secretion from rat gastric mucosa and other astringent effects (Ofuji etal., 1998), giving support to the traditional usage of Geranium for diarrhoea. They also exhibit strong antimutagenic effects against direct acting mutagens (Okuda et al, 1984). Like other tannin-containing drugs, extracts reduced levels of ureamic toxins, including creatinine, methyl-guanidine and guanidinosuccinic acid, in rats with renal failure (Yokozawa et al., 1995).
A considerable amount of research has been done on isolated geraniin, which has been shown to protect against experimental hepatic injuries in rats induced by galactosamine, carbon tetrachloride and thioacetamide (Nakanishi etal, 1998a). Geraniin also prevented the accumulation of liver triglycerides and lipid peroxide levels and lowered serum levels of hepatic enzymes associated with liver damage in the rat (Nakanishi et al, 1999a). A protective effect on oxidative damage to mouse ocular lens supports the traditional use for cataract to some extent (Fukaya etal., 1988). Haematological effects of geraniin in rats have also been studied, and a decrease in serum lipid levels observed as well as a reduction in erythrocytes and leucocytes (Nakanishi etal., 1998b). The effects of geraniin on aminonucleoside nephrosis in rats included a reduction in protei-nuria, and in serum and cholesterol levels produced by puromycin (Nakanishi etal, 1999b). Macrophages are known to be affected by geraniin, and marked increases in phagocytosis observed in in vitro cultures (Ushio et al, 1991). The clinical significance of some of these findings is not clear, and few human studies on Geranium herb are to be found in the literature, however the results of these various experiments show that the tannins it contains have pharmacological effects which may support its therapeutic use.
G. thunberghii contains tannins, the most important being geraniin, corilagin, dehydrogeraniin, furosin and furosinin, ellagic and gallic acids, geraniic acids B and C and phyllanthusiin F (Kan and Taniyama, 1992; Okuda et al, 1982; Ito et al, 1999).
44 Elizabeth Williamson
Geranium wilfordii Maxim, G. pratense L. and G. nepalense Sweet
G. wilfordii, or 'Lao-kuan-tsao' is used in Chinese medicine to treat chronic rheumatism, often steeped in wine and taken orally, either alone or in combination with other antirheumatic drugs. Erodium stephanium, also known as 'Lao Guan Cao', is considered interchangeable and used in a similar way (Pei-gen, 1989). The closely related Meadow Cranesbill, G. pratense ('Cao Yuan Lao Guan Cao') is used in traditional Chinese medicine to treat acute bacillary dysentery (Yau et al, 1999). G. nepalense is used in a similar manner to G. thunberghii, which is sometimes considered a variety of it (Perry, 1980).
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