Fingerprinting of propolis by easy ambient sonic-spray ionization mass spectrometry

Chemical profiles of a representative set of 49 propolis ethanolic extracts collected worldwide (North and South America, Europe, Asia and Oceania) were obtained via easy ambient sonic-spray ionization mass spectrometry (EASI-MS). This simple and easily implemented fingerprinting technique analyses directly (without any pre-separation or sample manipulation) a tiny droplet of the ethanolic extract placed on a inert surface under ambient conditions. Data acquisition took about a minute per sample with no substantial sample carry-over. Extraction of propolis with ethanol by using an ultrasonic bath method gave EASI-MS data similar to the traditional maceration method, reducing total analysis time for the crude propolis resin from a week to just ca 1h. Principal component analysis of the EASI-MS data is shown to group samples according to the plant sources of their resins, which characterizes their geographical origin.