The anti-inflammatory effects of ginger may be due to its effects on the arachidonic acid cascade, as COX-1 and -2 and lipoxygenase inhibition has been shown in vitro (Kobayashi et al 1987) and high oral doses of an aqueous extract of ginger (500 mg/kg) significantly lowered serum PGE2 and thromboxane B2 levels in rats (Thomson etal 2002).
Ginger also suppresses leukotriene biosynthesis by inhibiting 5-lipoxygenase, thus distinguishing ginger from NSAIDs. Additionally, ginger extract has been shown to inhibit thromboxane synthase (Langner et al 1998) and a ginger extract (EV.EXT.77) has been found to inhibit the induction of several genes involved in the inflammatory
response. These include genes encoding cytokines, chemokines, and the inducible enzyme COX-2, thus providing evidence that ginger modulates biochemical pathways activated in chronic inflammation (Grzanna et al 2005).
No one single constituent seems to be responsible for the anti-inflammatory effect of ginger. An acetone extract containing gingerols, shogaols and minor compounds like gingerenone A, -gingerdiol, hexahydrocurcumin and zingerone have been shown synergistically to produce dose-dependent anti-inflammatory effects (Schuhbaum & Franz 2000). Other studies have identified the gingerols and diarylheptanoids and gingerdione as the key compounds responsible (Flynn et al 1986, Kiuchi et al 1992).
Gingerol and 8-gingerol have been found to evoke capsaicin-like intracellular Ca2 + transients and ion currents in vitro and it has been suggested that gingerols represent a novel class of naturally occurring vanilloid receptor agonists that contribute to ginger's medicinal properties (Dedov et al 2002). This is supported by the finding that topical application of ginger creams or compresses produce an analgesic capsaicin-like effect on the release of the immunoreactive substance P from primary afferent neurons (Onogi et al 1992). In an animal study of chemically induced inflammation, ginger extract reduced oedema that was partly caused by serotonin-receptor antagonism (Penna et al 2003). Additionally, ginger oil has shown anti-inflammatory activity, significantly suppressing both paw and joint swelling in severe adjuvant arthritis in rats (Sharma et al 1994).
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