Variation of the phytoestrogen composition of red propolis throughout the year

Propolis is a resinous substance that bees collect from plants, and red propolis is mainly found in the northeastern states of Brazil. Isoflavonoids represent over 60% of the compounds in red propolis and are considered as phytoestrogens. In this study, the presence and identification of phytoestrogens were assessed by GC-MS, and the variation of those compounds was followed throughout one year. Twenty compounds, including six phytoestrogens and two phytosterols were identified in red propolis from the Brazilian states of Alagoas, Paraiba, Bahia, Sergipe, and Espirito Santo. The presence of these isoflavones was also observed in Dalbergia ecastophyllum collected in Brasilia and Paraiba, confirming that it is the botanical origin of these substances. No seasonal variation was observed in the presence of these phytoestrogens throughout the year, however, it was possible to cluster red propolis collected in different months according to their chemical composition.