Triterpene Alcohol and Sterol Ferulates from Rice Bran and Their Anti-inflammatory Effects

Abstract

Six novel feruloyl esters of triterpene alcohols and sterols, viz., two trans-ferulates, cycloeucalenol and 24-methylenecholesterol trans-ferulates, and four cis-ferulates, cycloartenol, 24-methyelenecycloartanol, 24-methylcholesterol, and sitosterol cis-ferulates, besides five known trans-ferulates, cycloartenol (CAR), 24-methylenecycloartanol (24-MCA), 24-methylcholesterol, sitosterol, and stigmastanol trans-ferulates, and one known cis-ferulate, stigmastanol cis-ferulate, were isolated from the methanol extract of edible rice bran. These and eight other synthetic trans- and cis-ferulates of triterpene alcohols and sterols, along with the corresponding free alcohols, were evaluated with respect to their anti-inflammatory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation (1 μg per ear) in mice. All of the ferulates showed marked inhibitory activity, and their 50% inhibitory dose (ID₅₀) was 0.1−0.8 mg per ear. On the other hand, whereas two free triterpene alcohols, CAR and 24-MCA, showed strong inhibition (ID₅₀ 0.2−0.3 mg/ear), eight free sterols examined showed weaker activity (ID₅₀ 0.7−2.7 mg/ear) than their corresponding ferulates. Keywords: Rice bran; trans- and cis-feruloyl esters; triterpene alcohol; sterol; antiedema; TPA-induced ear edema