A plant origin of Chinese propolis: Populus canadensis Moench

Honey bees make propolis from resins depending on resinous plants available in a particular environment. The aim of this work was to identify the plant origin of Chinese propolis. Through a combination of phytochemical analysis and behavior observation of worker bees, we find that worker bees collected resin on the bud surface of Populus canadensis Moench, and bud resin of P. canadensis presented high similarities between resin in worker bees’ corbiculae and propolis. The results reveal that P. canadensis, a hybrid variety of Populus nigra L. × Populus deltoides, is a plant origin of Chinese propolis. Characteristic components of Chinese propolis included benzyl caffeate, phenethyl caffeate, cinnamyl caffeate, cinnamyl p-cinnamate, pinobanksin-3-acetate, chrysin, pinocembrin, galangin, 5-methoxy pinobanksin, and pinobanksin. These compounds represented more than 80% of the total phenolic contents. This finding will help evaluate the quality and authenticity of poplar type propolis.