Glycyrrhizae radix has been used as one of the oldest and most frequently employed botanicals in both western and oriental countries. Previously, we showed that
liquiritigenin (LQ), an aglycone of
liquiritin in G. radix, exerts cytoprotective effects against
heavy metal-induced toxicity in vitro. This study investigated in vivo protective effects of LQ against acute liver
injuries induced by
acetaminophen (
APAP) or
APAP plus
buthionine sulfoximine (BSO). Liver
injuries were assessed by blood biochemistry and histopathology in rats administered with LQ purified from the
acid hydrolyates of
liquiritin singly (p.o. or i.v., 2-4 days) or in combination with dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate (
DDB), a synthetic derivative of
Schisandrin C in Fructus shizandrae, and exposed to
APAP or
APAP + BSO. LQ treatments (oral) effectively decreased liver
injuries induced by a single dose of
APAP, as evidenced by decreases in hepatic
necrosis and
inflammation as well as plasma
alanine aminotransferase and
lactate dehydrogenase activities. LQ, when intravenously applied, enhanced hepatoprotective effect with a greater potency.
APAP + BSO led to severe liver
injuries, resulting in lethality. LQ pretreatments significantly reduced the potentiated liver
necrosis, decreasing mortality. In spite of the improvement in blood biochemistry,
DDB failed to protect the liver from
injuries induced by
APAP or
APAP + BSO. Combined treatments of rats with LQ and
DDB showed some additive protective effect. The present study demonstrates that LQ efficaciously protects the liver from acute
injuries induced by
APAP or from
APAP-induced severe
injuries during GSH deficiency, indicating that LQ is one of the principal cytoprotective components comprised in G. radix.