Salicylic acid extraction and determination in some willow and poplar trees

In this study, it was aimed to create an optimum condition for the effective extraction of salicylic acid found naturally in willow and poplar trees and to develop a HPLC-UV method for the determination of salicylic acid and acetyl salicylic acid. The amount of the salicylic acid in willow and poplar trees extracts were determined with this developed method. Salicylic acid was first extracted with methanol in tree samples, and all extracts were washed with n-hexane to remove possible apolar compounds. Salicylic acid was drawn into dichloromethane solvent by liquid-liquid extraction method and the solvent was removed by using a rotary evaporator. The residue was dissolved in 1 mL acetonitrile and injected into the HPLC-UV system. The extraction efficiency was carried out with spiked samples, and it was 97.69% for salicylic acid and 98.72% for acetyl salicylic acid. Salicylic acid and acetyl salicylic acid were separated in a retention time of 9 minutes with the HPLC-UV method, and sharp and narrow peaks were obtained for each compound. The repeatability of the method in terms of retention time is lower than 0.10 min in standard deviation and 2% in relative standard deviation, in terms of peak areas is lower than 5% in relative standard deviation. The accuracy varies between 0.37% and 5.08% in relative error. The LOD and LOQ values of the method were 0.10 and 0.33 mg/L for salicylic acid and 0.2 and 0.67 mg/L for acetyl salicylic acid, respectively. After the optimization studies, the method has been successfully applied to tree samples. The amount of salicylic acid in willow and poplar trees samples varies between 1.75-8.00 mg/g. Keywords: Poplar tree, Willow tree, Salicylic acid, Acetyl salicylic acid, HPLC-UV