Ginsenoside Rf is a trace component of ginseng root. Ginsenoside Rf inhibits N-type Ca2+ channel.
Ginsenoside Rf is a saponin, which is present in only trace amounts within ginseng. At saturating concentrations, Ginsenoside Rf rapidly and reversibly inhibits N-type, and other high-threshold, Ca2+ channels in rat sensory neurons to the same degree as a maximal dose of opioids. The effect is dose-dependent (half-maximal inhibition: 40 μM) and it is virtually eliminated by pretreatment of the neurons with pertussis toxin, an inhibitor of G(o) and Gi GTP-binding proteins. Ginsenoside Rf also inhibits Ca2+ channels in the hybrid F-11 cell line[1].
Since inhibition of Ca2+ channels in sensory neurons contributes to antinociception by opioids, analgesic actions of Ginsenoside Rf are tested. Dose-dependent antinociception is found by systemic administration of Ginsenoside Rf in mice using two separate assays of tonic pain: in the acetic acid abdominal constriction test, the ED50 is 56±9 mg/kg, a concentration similar to those reported for aspirin and acetaminophen in the same assay; in the tonic phase of the biphasic formalin test, the ED50 is 129±32 mg/kg[2].
References:
[1]. Nah SY, et al. A trace component of ginseng that inhibits Ca2+ channels through a pertussis toxin-sensitive G protein. Proc Natl Acad Sci U S A. 1995 Sep 12;92(19):8739-43.
[2]. Mogil JS, et al. Ginsenoside Rf, a trace component of ginseng root, produces antinociception in mice. Brain Res. 1998 May 11;792(2):218-28.