Ginger has been known for centuries as a culinary spice and medicinal plant all over the world, and is used even more today. Arabic physicians knew it as Zanzabil and it was widely used by the Greeks and Romans.
The plant is widely cultivated in warm, moist areas of India, China, Sri Lanka, Nigeria, Jamaica and many south-east Asian countries.
It is a perennial herb with a stout, horizontal, tuberous, jointed, rootstock (Plate 70). The leaves are lanceolate, subsessile and glabrous, with a prominent midrib. The rhizome is thick and fleshy, laterally compressed, bearing short, ovate, oblique branches on the upper surface each having at its apex a depressed scar. Externally it is buff coloured with longitudinal striations. The flowers are yellowish-green, solitary, in oblong cylindrical spikes. The calyx is gamosepalous with three teeth at the apex and the corolla tube is cylindrical and three-lobed, greenish, subequal and lanceolate. The fruits are oblong capsules containing globose seeds.
The rhizome is used specifically for the treatment of rheumatism and inflammation. It is considered to be carminative, diuretic and aphrodisiac. It promotes digestive power, cleanses the throat and tongue, dispels flatulence and colic, suppresses vomiting and coughs, improves dyspnoea, anorexia, fever, constipation, swelling and dysurea. Ginger is valuable in many painful affections of the stomach and bowels and for cold, cough, asthma, dyspepsia and indigestion.
The rhizome is used in coughs and colds, eye diseases, retained placenta, bloat, diarrhoea and sprains in poultry, ruminants. The leaves and rhizome are used as a preventive for mastitis and to treat wounds, haemorrhagic septicaemia, pneumonia, asthma, coughs, swelling of the nasal mucous membranes, stomach pain, tympanitis, constipation, dysentery, loss of appetite, lumbar fracture and stoppage of urination.
The pungent components are a series of gingerols, gingerdiols and gingerdiones and their dehydration products, the shogaols.
Major constituents of the essential oil are the monoterpenes ?-phellandrene, perillaldehyde, neral and geranial and the sesquiterpenes a-zingiberene, ?-santalol, 13?bisabolene, a-curcumene, zingiberol, nerolidol, ?-eudesmol, farnesol, elemol and zingerone.
Antiemetic activity: Ginger was found to be superior to dimenhydrinate in preventing motion sickness and the gingerols and shogaols were identified as the main antiemetic principles. Studies suggest that the action of ginger modulated vestibular impulses to the autonomic centres of the central nervous system. In a study of 30 pregnant women, in a double-blind randomised cross-over trial, it was observed that powdered root ginger was superior to placebo in reducing the symptoms of hyperemesis gravidarum (morning sickness)
Antiulcer activity: ?-Sesquiphellandrene, ?bisabolene, curcumene, 6-gingesulphonic acid and 6-shogaol were identified as antiulcer active principles from the dried rhizome when tested against hydrochloric acid or ethanol-induced gastric lesions in rats. 6-Gingesulphonic acid was found to be the most potent compound. Antihepatotoxic activity: Protection by the gingerols and shogaols against carbon tetrachloride- and galactosamine-induced toxicity was observed in cultured rat hepatocytes.
Antiinflammatory activity: An ethanolic extract of the rhizome reduced carrageenan?induced paw swelling and yeast-induced fever in rats, but was ineffective in suppressing the writhing induced by acetic acid. The essential oil inhibited chronic adjuvant arthritis in rats.
Antiplatelet activity: An aqueous extract of ginger inhibited platelet aggregation induced by ADP, epinephrine, collagen and arachidonic acid in vitro and inhibited prostacyclin synthesis in rat aorta. It is thought to act by inhibiting thromboxane synthesis;IO 6-gingerol acts in a similar manner.
Antipyretic activity: Oral administration of ginger extract reduced fever in rats by 38% as compared to aspirin (where 44% reduction was observed), as did 6-shogaol and 6?gingerol. Ginger is also used for the treatment of migraine headaches and a mechanism of action via the inhibition of prostaglandin and thromboxane synthesis was proposed. However, in contrast to feverfew (Tanacetum parthenium), ginger did not inhibit serotonin release from bovine platelets.
Cardiovascular activity: Ginger decreased serum and hepatic cholesterol and inhibited cholesterol biosynthesis levels in cholesterol?fed rats. It also stimulated bile acid biosynthesis from cholesteroL Ginger had a positive inotropic effect on isolated guinea pig atria and 6-shogaol showed pressor response.
Hypolipidaemic activity: An ethanolic extract of ginger reduced hyperlipidaemia induced by an atherogenic diet. A reduction in the levels of serum and total cholesterol, serum triglycerides and phospholipids and an increased coagulation time were observed when compared with the control group. The extract of ginger was comparable to gemfibrozil.
Antioxidant activity: The pungent principles, including gingerop and zingerone, demonstrated in vitro effects in scavenging the superoxide and hydroxyl radicals and inhibiting lipid peroxidation. Immunomodulatory activity: Humoral immunity was enhanced, as shown by humoral antibody titre, and cell-mediated response was also stimulated in leucocyte migration inhibition tests.
Thermogenic activity: Studies suggest that the pungent principles of ginger stimulate thermoregulatory receptors. Zingerone induced catecholamine secretion from the adrenal medulla in vivo and thus induced a warming action. 6-Gingerol was one of the more potent compounds isolated.
Antiviral activity: ?-Sesquiphellandrene exhibited significant antirhinoviral activity against rhinovirus B in vitro.
Nematocidal activity: 6-Shogaol and 6?gingerol were lethal to Anisakis larvae at doses of 62.5 and 250 Ilg/mL A synergistic effect appeared to exist between the two compounds.
Insect repellent activity: The essential oil was found to be highly repellent to the cockroach, Periplaneta americana, and the agricultural pest Bruchus pisorum.
Molluscicidal activity: Gingerol and shogaol exhibited potent molluscicidal activity against Biomphalaria glabrata. At a concentration of 5 ppm gingerol completely abolished the infectivity of Schistosoma mansoni miracidia and cercariae in the snail host and in mice.
It is generally considered as safe (GRAS). Pregnancy has been considered to be a contraindication (although there is no evidence to support this and it has been demonstrated to be helpful in allaying nausea of pregnancy) as it could potentially induce uterine contractions.
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