Korean red ginseng has been shown to possess a variety of
biological activities. However, little is known about
antiviral activity of
ginsenosides of Korean red ginseng. Here, we investigated the protective effect by
oral administration of various
ginsenosides on the lethal
infection of haemagglutinating virus of Japan (HVJ) in mice. In a lethal
infection model in which almost all mice infected with HVJ died within 15 days, the mice were administered orally (per os) with 1 mg/mouse of
dammarane-type (ginsenoside-Rb1, -Rb2, -Rd, -Re, and -Rg2) or
oleanolic acid-type (
ginsenoside-Ro)
ginsenosides 3, 2, and 1 d before
virus infection. Ginsenoside-Rb2 showed the highest protective activity, although other
dammarane-type and
oleanolic acid-type
ginsenosides also induced a significant protection against HVJ. However, neither the consecutive administration with a lower dosage (300 μg/mouse) nor the single administration of ginsenoside-Rb2 (1 mg/mouse) was active. In comparison of the protective activity between ginsenoside-Rb2 and its two hydrolytic products [20(S)- and 20(R)-
ginsenoside-Rg3], 20(S)-ginsenoside-Rg3, but not 20(R)-ginsenoside-Rg3, elicited a partial protection against HVJ. The protective effect of ginsenoside-Rb2 and 20(S)-ginsenoside-Rg3 on HVJ
infection was confirmed by the reduction of virus titers in the lungs of HVJ-infected mice. These results suggest that ginsenoside-Rb2 is the most effective among
ginsenosides from red ginseng to prevent the lethal
infection of HVJ, so that this
ginsenoside is a promising candidate as a mucosal
immunoadjuvant to enhance
antiviral activity.