Hofmeisteria schaffneri is used in Mexican folk medicine for treating painful gastric complaints. Therefore, in this paper the smooth muscle relaxant effect of the essential oil, and an infusion of the whole plant were evaluated using the gastrointestinal transit test in mice. The results revealed that both preparations at 316 mg/kg inhibited gastrointestinal transit by 47.5 and 52.1%, respectively. The common component of the infusion and essential oil was 8,9-epoxy-10-acetoxythymol angelate (2), which inhibited the gastrointestinal transit by 53.4% at a dose of 31.6 mg/kg. An HPLC-UV method was developed and validated to quantify 2. The chromatographic conditions were: A LiChrospher® 100 RP-18 column (250 × 4 mm i.d., 5 μm) with a mobile phase composed of CH3CN-H2O, in a gradient run at a flow rate of 0.6 mL/min, using a wavelength of 215 nm. The method was linear, precise, accurate, and showed excellent recovery. According to the results, compound 2 can be used as a marker for the quality control procedures of the crude drug of H. schaffneri.
