Although this method is very rapid and convenient for determining the MIC of a large number of samples within 2 hours, it is sometimes difficult to use for toxin samples. Most of the cyanobacterial toxin samples contain colouring materials due to the presence of chlorophyll b which causes abnormal absorbance value. Therefore, it is better to remove the colouring materials from the toxin samples for determination of
MIC by FDA method. Charcoal can be used to remove colour. Due to charcoal’s adsorption activity,
colouring materials can bind with it and the samples can be decolorized by filtration. Again, charcoal may
absorb compound of interest too. So special care should taken during handling charcoal
The LC50 values of 25%, 50% and 75% aqueous MeOH fraction of M. aerugionosa had reasonable
LC50 values with 32, 36 and 78 ìg/mL, respectively. Other fractions had moderate activity with LC50
values in the range of 118-176 ìg/mL. The significant toxic activity of fractions of M. aerugionosa might be due to the presence of more toxins. The LC50 value of microcystin LR was found to be 3.2 ìg/mL.