3.5. Chemical analysis of hexane extract using UPLC
UPLC analysis was conducted to detect the non-volatile com-pounds that were not detected by GC–MS in the hexane extract.The extract was dissolved in methanol and defatted using diethylether to remove the volatile compounds,which were detected by GC–MS. Fig. 3 shows the UPLC chromatogram (at 320 nm) of the extract and the UV spectra of two peaks as indicated by the photo diode array detector.However,both peaks were negatively identified by comparisons with standards.The UV spectrum of the peak (UV λmax 242.6 and329.5nm) at the retention time of 3.501 min was most likely a derivative of caffeic acid,and the UV spectrum of the peak(UV λmax 267.1and338.1nm) at the retention time of 4.973 min was very similar to those of apigenin derivatives.