Green Tea, Leurel and St. John’s Wort were used as real samples.
1.0 g of each pharmaceutical plant material was extracted with
100 mL of pure methanol using an ultrasonic bath for 2 h. The
temperature of the methanol during the extraction was 40 C in
atmospheric pressure. The solution was cooled and filtered using
a125-mm of What-man filter paper. After filtration, the obtained
solution was adjusted to the volume of 1000 mL with the
methanol. In order to get the suitable concentration for the UV
measurements, the solution was further diluted