2. Experimental
2.1 Samples
Propolis samples were supplied friendly by By-health Co. Ltd, which were collected during summer
2017 from different manufacturers (Figure 1) and stored at -20℃ until analysis.
2.2 Reagents and chemicals
Methanol (HPLC grade), formic acid (HPLC grade) and ethanol (95%) were purchased from Merck
Chemicals (Darmstadt, Germany).
2.3 Preparation of reference substance solution
Reference substance of chlorogenic acid, caffeic acid, isochlorogenic acid B, isochlorogenic acid C,
caffeic acid phenethyl ester, myricetin, quercitrin, kaempferol, apigenin, pinocembrin and galangin
were supplied by Chengdu Alfa Biotechnology Co.,Ltd. (Chendu, China).