Plant origin authentication of Sonoran Desert propolis: an antiproliferative propolis from a semi-arid region

The main chemical composition of Sonoran propolis (SP), as well as its antiproliferative activity on cancer cells through apoptosis induction, has been reported. The chemical constitution of SP remained qualitatively similar throughout the year, whereas the antiproliferative effect on cancer cells exhibited significant differences amongst seasonal samples. The main goal of this study was to provide phytochemical and pharmacological evidence for the botanical source of SP and its antiproliferative constituents. A chemical comparative analysis of SP and plant resins of species found in the surrounding areas of the beehives was carried out by HPLC-UV-DAD, as well as by 1 H NMR experiments. The antiproliferative activity on cancerous (M12.C3.F6, HeLa, A549, PC-3) and normal cell lines (L-929; ARPE-19) was assessed through MTT assays. Here, the main polyphenolic profile of SP resulted to be qualitatively similar to Populus fremontii resins (PFR). However, the antiproliferative activity of PFR on cancer cells did not consistently match that exhibited by SP throughout the year. Additionally, SP induced morphological modifications on treated cells characterised by elongation, similar to those induced by colchicine, and different to those observed with PFR treatment. These results suggest that P. fremontii is the main botanical source of SP along the year. Nevertheless, the antiproliferative constituents of SP that induce that characteristic morphological elongation on treated cells are not obtained from PFR. Moreover, the presence of kaempferol-3-methyl-ether in SP could point Ambrosia ambrosioides as a secondary plant source. In conclusion, SP is a bioactive poplar-type propolis from semi-arid zones, in which chemical compounds derived from other semi-arid plant sources than poplar contribute to its antiproliferative activity.