title: A Systematic Review of the Uterine Relaxant Effect of Herbal Sources.
abstract: BACKGROUND
  Preterm birth is a worldwide tragedy with a high incidence. Several medications are used to inhibit acute preterm labor, but tocolysis by these medicines do not extend pregnancy beyond 1-2 days.
  
  
  OBJECTIVE
  The purpose of this study was to discover new medications from plant extracts or their active compounds which inhibit the uterine contractions in order to treat preterm labor.
  
  
  METHODS
  PubMed, Google Scholar, Scopus and IranMedex databases were searched up to 1st February 2012 with the most relevant keywords.
  
  
  METHODS
  All studies in which plant extracts or their active compounds inhibited the uterine contractions both in vivo and in vitro were included.
  
  
  RESULTS
  Of initial search, 259 records were reviewed and finally 72 were included among which only 31 studies isolated an active compound from the plants extract belonging mostly to classes of flavonoids and terpenes classes. Flavonoids have been known as a phosphodiesterase (PDE) and a protein kinase C (PKC) inhibitor. It seems that the uterolytic activity of reviewed flavonoids such as naringenin, kaempferol and quercetin, especially in a calcium free solution, was via these inhibitory pathways.
  
  
  CONCLUSIONS
  Laboring uterus response to dissimilar tocolytics differs from that of non-laboring uterus. In order to find a treatment for preterm labor, future studies should focus on the laboring uterus and also determine the structure activity relationship of the different tocolytics. This systematic review was registered to the PROSPERO with code number CRD42015027551.
authors.forename: Golnaz
authors.initials: G
authors.lastname: Rezaeizadeh
authors.forename: Sedigheh
authors.initials: S
authors.lastname: Hantoushzadeh
authors.forename: Sima
authors.initials: S
authors.lastname: Ghiasi
authors.forename: Shekoufeh
authors.initials: S
authors.lastname: Nikfar
authors.affiliation: Faculty of Pharmacy and Pharmaceutical Sciences Research Center, TUMS, Tehran 1417614411, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Abdollahi
mesh_terms: D000818:Animals; D005260:Female; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology; D007752:Obstetric Labor, Premature / Q000175:diagnosis / Q000517:prevention & control*; D028321:Plant Preparations / Q000302:isolation & purification / Q000494:pharmacology / Q000627:therapeutic use*; D011247:Pregnancy; D015149:Tocolytic Agents / Q000302:isolation & purification / Q000494:pharmacology / Q000627:therapeutic use*; D014590:Uterine Contraction / Q000187:drug effects* / Q000502:physiology
chemical_list: D005419:Flavonoids; D028321:Plant Preparations; D015149:Tocolytic Agents