Characterization of Chinese crude propolis by pyrolysis–gas chromatography/mass spectrometry

Abstract

A method for analysis of Chinese crude propolis was developed by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) with a vertical microfurnace pyrolyzer. Propolis sample powder about 0.1mg was pyrolyzed directly at the optimum pyrolytic temperature of 550°C without any time-consuming pretreatments. 76 compounds were identified on the resulting pyrogram after the pyrolysis of crude propolis, and all the compounds were grouped into 8 categories such as flavonoids, terpenoids, acids, esters, hydrocarbons, phenols and alcohols, aldehydes and ketones, and others. On the basis of peak areas, the relative intensities of 76 peaks were precisely determined with the relative standard deviations (RSDs (%), n=3) between 1.1 and 14.0%. Furthermore, the compositions of crude propolis samples from different geographical regions in China were analyzed and compared. The contents of 8 categories of compounds in crude propolis samples were different, the predominant categories being flavonoids, esters or hydrocarbons. And also the contents of main bioactivity compounds such as flavonoids and terpenoids were extremely different, and varied largely with 0–54.9% and 0.6–21.6%, respectively. In addition, abundant triterpenoids were identified in Chinese propolis for the first time. It is proved that Py–GC/MS is a simple, rapid and sensitive method for the characterization of the crude propolis.