This study was carried out to investigate the acute oral toxicity of Chamaecyparis obtusa (C. obtusa) essential oil (CBE) in New Zealand white male and female rabbits. Acute oral treatment with the CBE did not reveal any sign of toxicity or mortality in treated rabbits. The body weight of the rabbits was not affected after a single oral administration of the CBE during the 14-day observation period. In both the hematological and blood biochemical analysis, all parameters of the treated group with 2,000 mg/kg body weight of the CBE were not significantly different than those of the control group. Therefore, the lethal dose 50 of the CBE was estimated to be greater than 2,000 mg/kg body weight in rabbits, which indicated that the CBE is non-toxic. In conclusion, this study suggests that oral administration of the CBE is safe on rabbits.

Taxifolin-3-O-β-D-xylopyranoside and quercetin-3-O-α-L-rhamnopyranoside were isolated from an EtOAc-soluble extract of the leaves of Chamaecyparis obtuse. Quercetin-3-O-α-L-rhamnopyranoside was found to possess a potent inhibitory activity of human recombinant aldose reductase in vitro, its IC50 value being 11.5 μM. Kinetic analysis showed that quercetin-3-O-α-L-rhamnopyranoside exhibited uncompetitive inhibition against DL-glyceraldehyde. Also, quercetin-3-O-α-L-rhamnopyranoside suppresses sorbitol accumulation in rat lens under high glucose conditions, demonstrating the potential to prevent sorbitol accumulation in vivo. These results suggest that this compound may be a promising agent in the prevention or treatment of diabetic complications.