Two acetylmartynosides, 2"-acetylmartynoside and 3"-acetylmartynoside were isolated from the $CH_2Cl_2$ fraction of Clerodendron trichotomum (Verbenaceae) by open column chromatography and MPLC. Their chemical structures were identified by the direct comparison of spectral data reported in the literature, and their antioxidant properties were evaluated. Both compounds showed antioxidant activity based on evaluations of intracellular ROS and DPPH radical scavenging activities.