In vitro activity of neem (Azadirachta indica) oil extract against Helicobacter pylori

J Ethnopharmacol. 2019 Mar 25:232:236-243. doi: 10.1016/j.jep.2018.12.025. Epub 2018 Dec 19.


Ethnopharmacological relevance: The neem tree (Azadirachta indica A.Juss), of the Meliaceae family, has been used in India for millennia in traditional medicine. Parts of the tree are used to treat problems with the gastrointestinal tract, urinary tract, and hair; to combat infections of smallpox and plasmodium; and to treat ulcers, diabetes, blood pressure, headache, and heartburn. Natural products and extracts from the tree have been reported to have antimicrobial, antifungal, and antiparasitic activities.

Aim of the study: Antibiotic resistance in the gastric pathogen Helicobacter pylori is increasing, and novel therapeutics to eradicate this bacterium are needed. Given the growing interest in the use of natural products as antimicrobials, this study was designed to examine the bactericidal effects of an extract of neem oil against H. pylori.

Materials and methods: Neem oil was obtained from a commercial source and subjected to liquid-liquid extraction with diethyl ether and aqueous methanol; the methanol-soluble fraction was retained. The minimum inhibitory (MIC) and bactericidal (MBC) concentrations were determined against nine strains of H. pylori. Additionally, specific properties of the extract were characterized using H. pylori strain G27: bactericidal kinetics, reversibility, and effectiveness under growth arrest conditions and at low pH. The hemolytic activity of the extract was measured in vitro.

Results: The MIC and MBC of the extract against the H. pylori strains were between 25 and 51 µg/mL and 43-68 µg/mL, respectively. The bactericidal activity was time- and concentration-dependent, and at the highest concentrations (75-105 µg/mL), no detectable bacteria were present by 6 h. The activity of the extract was reversible, independent of H. pylori growth, and increased at low pH. The extract exhibited no appreciable hemolytic activity.

Conclusions: Neem oil extract has significant bactericidal activity against H. pylori. The extract has several favorable pharmacological properties, including ability to kill non-growing bacteria, increased activity at low pH, and no hemolytic activity. The compound(s) present in the extract could potentially be used as a future treatment for H. pylori infection.

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Erythrocytes / drug effects
  • Glycerides / pharmacology*
  • Helicobacter pylori / drug effects*
  • Helicobacter pylori / growth & development
  • Horses
  • Hydrogen-Ion Concentration
  • Microbial Sensitivity Tests
  • Terpenes / pharmacology*


  • Anti-Bacterial Agents
  • Glycerides
  • Terpenes
  • neem oil