The content of essential and toxic elements in Croatian propolis samples and their tinctures

There is a general lack of scientific literature dealing with the mineral composition of propolis, despite the fact that the presence of minerals in plant tissues can significantly affect the pharmacotherapeutic properties of derived products. Raw propolis samples collected from different Croatian regions and their respective tinctures were therefore analysed for mineral composition by atomic emission / absorption spectrometry. Contents of macro- and trace elements (Ca, K, Mg, Na, Al, B, Ba, Cr, Cu, Fe, Min, Ni, Sr and Zn) were determined. Levels of toxic elements (As, Cd, Hg, and Pb) were also analysed, since they are possible environmental contaminants that could be transferred into propolis products for human consumption. Following the European Pharmacopoeia requirements for quality control of herbal drugs, crude propolis samples were also analysed for total ash content. Significant correlation between the total mineral content and total ash of raw propolis (r = 0.9273) showed that total ash might serve as the first information that justifies the need for detailed mineral analysis of tested samples. Among analysed minerals, Ca, Mg, K, Al, Fe and Zn were found to be the most abundant in raw propolis, ranging from 12.06 (Mg) to 932.6 mg/100g (Zn). Mineral contents of all investigated tinctures were significantly lower compared to the respective raw propolis samples. Extractability was variable due to influence of the sample matrix and correlated with the mineral content of raw propolis only in the case of Fe, Mg, Sr and Zn. All samples met the World Health Organization (WHO) standards regarding the maximum permitted amounts of Hg, Pb, As and Cd except for two raw propolis samples with increased lead content indicating pollution of the collection areas.