title: Antibacterial activities of chemical constituents from the aerial parts of Hedyotis pilulifera.
abstract: BACKGROUND
  Hedyotis pilulifera (Pit.) T.N. Ninh (Rubiaceae) has been used in Vietnamese ethnomedicine; the methanol extract exhibited antibacterial activity in our preliminary screening.
  
  
  OBJECTIVE
  In this study, compounds from H. pilulifera were isolated and their antibacterial activity in vitro was evaluated.
  
  
  METHODS
  The aerial parts of H. pilulifera (1.4 kg) were extracted with MeOH, suspended in water and ethyl acetate extract was chromatographed on a silica gel column. The structures of isolated compounds were elucidated by the combination analyses of spectroscopy including 1D-, 2D-NMR, HRMS and in comparison with the reported NMR data in the literature. All isolated compounds were evaluated for inhibitory effect using the microdilution method toward Staphylococcus aureus, Bacillus subtilis and Mycobacterium smegmatis, and MIC values were determined.
  
  
  RESULTS
  Twenty compounds were isolated, including five triterpenoids, two steroids, two aromatic compounds, three fatty acids, one quinone derivative, one lignan glycoside, one ceramide and five glycolipids. Among these, oleanolic acid showed significant antibacterial activity against M. smegmatis with the MIC value of 2.5 μg/mL. Remarkably, rotungenic acid showed strong activity against S. aureus, B. subtilis, M. smegmatis with MIC values of 2.5, 2.5 and 1.25 μg/mL, respectively. Rotundic acid exhibited significant antibacterial activity against B. subtilis with the MIC value of 5 μg/mL. To the best of our knowledge, the antibacterial activity of rotungenic acid, stigmast-4-ene-3,6-dione and (2S,3S,4R,2'R)-2-(2'-hydroxytetracosanoylamino) octadecane-1,3,4-triol was reported for the first time.
  
  
  CONCLUSIONS
  Oleanolic acid, rotungenic acid, and rotundic acid were considered to be useful for developing new antimicrobial therapeutic agents for human.
authors.affiliation: a Faculty of Pharmacy , Hue University of Medicine and Pharmacy , Hue University, Hue City , Vietnam.
authors.forename: Hoai Thi
authors.initials: HT
authors.lastname: Nguyen
authors.affiliation: a Faculty of Pharmacy , Hue University of Medicine and Pharmacy , Hue University, Hue City , Vietnam.
authors.forename: Duc Viet
authors.initials: DV
authors.lastname: Ho
authors.affiliation: a Faculty of Pharmacy , Hue University of Medicine and Pharmacy , Hue University, Hue City , Vietnam.
authors.forename: Hung Quoc
authors.initials: HQ
authors.lastname: Vo
authors.affiliation: b Quang Tri Center of Science and Technology, Mientrung Institute for Scientific Research , Quang Tri , Vietnam.
authors.forename: Anh Tuan
authors.initials: AT
authors.lastname: Le
authors.affiliation: c Institute of Natural Medicine, University of Toyama , Toyama , Japan.
authors.forename: Hien Minh
authors.initials: HM
authors.lastname: Nguyen
authors.affiliation: c Institute of Natural Medicine, University of Toyama , Toyama , Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kodama
authors.affiliation: c Institute of Natural Medicine, University of Toyama , Toyama , Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Ito
authors.affiliation: c Institute of Natural Medicine, University of Toyama , Toyama , Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Morita
authors.affiliation: d Institute of Pharmacy, University of Tartu , Tartu , Estonia.
authors.forename: Ain
authors.initials: A
authors.lastname: Raal
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000302:isolation & purification* / Q000494:pharmacology; D032064:Hedyotis / Q000737:chemistry*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D035261:Plant Components, Aerial / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry* / Q000302:isolation & purification* / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000502:physiology
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts
keywords: Oleanolic acid; Staphylococcus aureus; Bacillus subtilis; Mycobacterium smegmatis; rotundic acid; rotungenic acid