Effect of essential oil concentration on the pH of nutrient and Iso-sensitest broth.
The role of pH on the antimicrobial activity of essential oils has not been well studied. The effect of four essential oils: Backhousia citriodora, Melaleuca alternifolia, Lavandula angustifolia and Santalum spicatum (0.1% to 10%) on the pH of two commonly used media, nutrient broth and Iso-sensitest broth, was therefore undertaken. Small (less than 0.5 pH units) but statistically significant differences between the pH of the two media followed the addition of M. alternifolia, L. angustifolia and S. spicatum essential oil. In general the effect on pH was greatest at higher concentrations and the fall in pH was greatest in the nutrient broth. The addition of B. citriodora essential oil to nutrient broth resulted in a fall in pH from 7.29 +/- 0.02 (no oil) to 5.2 +/- 0.03 (10% oil). This effect was not observed in the Iso-sensitest broth.
Hood
J R
JR
School of Biomedical Sciences, Charles Sturt University, Australia.
Cavanagh
H M A
HM
Wilkinson
J M
JM
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001419:Bacteria / Q000254:growth & development; D003470:Culture Media / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D027523:Lavandula; D031650:Melaleuca; D008826:Microbial Sensitivity Tests / Q000592:standards; D027822:Myrtaceae; D008517:Phytotherapy; D010938:Plant Oils / Q000737:chemistry*; D010946:Plants, Medicinal; D032123:Santalum
D000900:Anti-Bacterial Agents; D003470:Culture Media; D010938:Plant Oils