Determination of biologically active phenolic compounds in propolis by LC-MS/MS according to seasons and altitudes

The present study aimed to determine the effect of season and altitude to amount and prevalence of phenolic compounds in propolis. For the aim, 174 propolis samples were collected from 58 stationary apiaries from altitudes of 0-200 m, 200-500 m and above 500 m in spring, summer, and autumn distributed in the Marmara region of Turkey. Ethanol-extracted propolis samples were analyzed by LC-MS/MS to determine nine flavonoids and seven phenolic acids. Significant differences were found in average levels of galangin, naringenin, pinocembrin, quercetin, luteolin, caffeic acid, trans-cinnamic acid, p-coumaric acid, m-coumaric acid, and CAPE across the seasons and altitudes (P < 0.05). However, no differences were found levels of rutin, apigenin, kaempferol, ferulic acid and gallic acid (P < 0.05). Most of the significant differences were found between spring and autumn (10 differences). The prevalence of flavonoids was generally lower than phenolic acids. CAPE and pinocembrin had majority of the significant differences in phenolic compounds according to season and altitude. The prevalence of pinocembrin 100%, m-coumaric acid 99.4%, CAPE 99.4%, naringenin 99.4%, caffeic acid 98.9%, p-coumaric acid 98.3%, quercetin 96% and luteolin 95.4% were determined that dominant phenolic compound of Marmara Region of Turkey's propolis. Furthermore, Salix spp. 75.8%, Quercus spp. 74.4%, Populus spp. 72.4%, and Pinus spp. 53.5% were mainly determined source of propolis around the apiaries. These results show that different sampling of seasons and altitudes effect chemical composition of propolis even from the same area. The study indicated that seasons and altitudes are important factors for standardization of propolis.