Determination of minimum inhibitory
concentration (MIC)
The MIC for each sample was
determined using the disc diffusion method.
Concentrated extracts of turmeric (ethanol
turmeric extract, hexane turmeric extract and
curcuminoids) were added at two-fold serial
dilution with DMSO (0.244 to 1000 ppt). Each
diluted solution was applied to sterile filter paper
discs (Whatman grade AA discs size 6 mm in
diameter) and placed on the surface of the assay
plates, which were then incubated at 37°C for 24
h. MIC values were taken as the lowest
concentration of extract that completely inhibited
bacterial growth or produced a clear zone on the
disc that was bigger than the negative control (pure
DMSO) disc after 24 h of incubation at 37°C.