The aim of this research was to investigate theantibacterial activity of Clerodendron trichotomum. Antibacterialactivities of the n-hexane, methylene chloride (MC), ethyl acetate,and n-butanol fractions from C. trichotomum were tested againstStaphylococcus aureus, Escherichia coli, and Helicobacter pylori.The n-hexane and MC fractions showed antibacterial activityagainst H. pylori at a concentration of 1.7 mg/mL and showedinhibition zones of 10 and 11 mm in disc assay, respectively.Further testing of 22-dehydroclerosterol and β-amyrin (each 3.4mg/mL) from the MC fraction of C. trichotomum revealedmoderate antibacterial effects against E. coli, S. aureus, and H.pylori. In particular, β-amyrin showed clear zones of 12 and 13mm against E. coli and H. pylori, respectively, suggesting itspotential as an antibacterial agent. The active compounds from C.trichotomum might provide a promising therapeutic agent againstinfections by E. coli, S. aureus, and H. pylori.Keywords antibacterial activity ·β-amyrin · Clerodendron trichotomum · 22-dehydroclerosterolIntroductionVarious pathogenic bacteria including Escherichia coli andStaphylococcus aureus are responsible for infectious diseases. E.coli is a common cause of urinary tract infections and bacteremiain humans, and is frequently resistant to aminopenicillins, such asamoxicillin and ampicillin (Allen et al., 1999; Karlowsky et al.,2002; Landgren et al., 2005). In addition, S. aureus is a commoncause of infection in hospitalized patients (Westh et al., 2004). Theouter cell membranes of Gram-negative bacteria such as E. coliare known to be covered with a lipopolysaccharide layer 1–3 µmin thickness, while the surfaces of Gram-positive bacteria such asS. aureus have a peptidoglycan layer, to which teichoic acid,teichuronic acid, and proteins are covalently bound (Sonohara etal., 1995). Helicobacter pylori, a Gram-negative bacterium, invokespro-oxidant and pro-inflammatory mechanisms that may lead tochronic conditions such as gastritis, peptic ulcers, and gastric cancer.The clinical efficacy of many existing antibiotics is beingthreatened by the emergence of multidrug-resistant pathogens(Bandow et al., 2003). Plant products, either as pure compoundsor as standardized extracts, provide promising opportunities fornew anti-infective drugs. There is an urgent need to discover newantimicrobial compounds with diverse chemical structures andnovel mechanisms of action for use in the treatment of new andre-emerging infectious diseases (Rojas et al., 2003). Therefore,researchers are increasingly turning their attention to naturalproducts as a source for new and better antimicrobial drugs(Benkeblia, 2004; Kang et al., 2005).Clerodendron trichotomum Thunb., whose Japanese name isKusagi and which belongs to the Verbenaceae family, grows wildin the fields and mountains of Korea, Japan, and China (Inchi etal., 1996; Lee, 1996). C. trichotomum is a deciduous shrub, growing10−15' tall in warmer climates and regarded as an herbaceousperennial in cold northern climates. While in flower or whilefruiting it is quite beautiful, but is not very appealing otherwise, asit tends to die back and appear unkempt. It tends to flower in thesummer time, producing white, 1 1/2"-wide flowers in clusteredcymes, 6−9" across. The fruit is a small bright blue drupe framedby a reddish leathery calyx. The dried leaf and stem of C.trichotomum, known as ‘Chou Wu Tong’, exhibits diverse