Pyrrolizidine alkaloids in pollen and pollen products

Abstract

Recently, 1,2-dehydropyrrolizidine alkaloid (PA) ester alkaloids, found predominantly as their N-oxides (PANOs, pyrrolizidine N-oxides), have been reported in both honey and in pollen obtained directly from PA plants and pollen loads collected by bees, raising the possibility of health risks for consumers of these products. We confirm these findings in regard to floral pollen, using pollen collected directly from flowers of the known PA plants Senecio jacobaea, S. vernalis, Echium vulgare and pollinia of Phalaenopsis hybrids, and we extend analyses of 1,2-unsaturated PAs and 1,2-unsaturated PANOs to include bee-pollen products currently being sold in supermarkets and on the Internet as food supplements. PA content of floral pollen ranged from 0.5 to 5 mg/g. The highest values were observed in pollen obtained from Senecio species. Up to 95% of the PAs are found as PANOs. Detailed studies with S. vernalis revealed unique PA patterns in pollen and flowers. While seneciphylline was the most prominent PA in S. vernalis pollen, the flowers were dominated by senecionine. To analyze trace amounts of 1,2-unsaturated PAs in pollen products, our previously elaborated method consisting of strong cation exchange-SPE, two reduction steps followed by silylation and subsequent capillary high-resolution GC-MS using SIM mode was applied. In total, 55 commercially available pollen products were analyzed. Seventeen (31%) samples contained 1,2-unsaturated PAs in the range from 1.08 to 16.35 microg/g, calculated as retronecine equivalents. The 1,2-unsaturated PA content of pollen products is expressed in terms of a single sum parameter and no background information such as foraged plants, pollen analysis, etc. was needed to analyze the samples. The detection limit of overall procedure and the reliable quantitation limit were 0.003 and 0.01 microg/g, respectively.

Pyrrolizidine alkaloids in food: downstream contamination in the food chain caused by honey and pollen

“…These results are summarized in Figure 1.If the extraction time was 24 hrs, the recovery rate was significantly lower (56 to 70%) and the deviation in reproducibility rate much higher (21-34%) as compared to 78-88% (recovery rate) and 5-11% (deviation in reproducibility) for 48 hrs extractions. By increasing the amount of initial sample weight and additional expenditure during sample clean-up the LOQ could be maintained at 0.01 ppm (S/N = 7:1) as reported earlier (Kempf et al 2008;Kempf et al 2010b) and the varied method could be applied successfully to all different kinds of matrices.…”

“…Floral Senecio vernalis pollen (pollen PA-content: 1.85 ± 0.13 mg g -1 , calculated as retronecine equivalents; cf. Kempf et al 2010b) was added to 1000 g honey and was stirred until a homogenous were sampled at defined time points: day 1, 6 wks and 12 wks (day 1, only as unfiltered sample) and were analyzed for PA-content after filtration. A second set of honey samples was analyzed without filtration.…”

“…Recent studies have demonstrated significant amounts of PAs in floral pollen of PA-plants (Boppré et al 2008;Kempf et al 2010b). Therefore, PA pollen is discussed as the only source or as major contributor to PA-contamination of honey (Edgar et al 2002;Boppré et al 2005;Kempf et al 2010a).…”

“…Senecio vernalis with a known PA-content (1.85 ± 0.13 mg g -1 , calculated as retronecine equivalents; Kempf et al 2010b) to PA-free honey. Three typical pollen concentrations were added to PA-free honey, 3 mg kg -1 (representing regular amounts of pollen), 30 mg kg -1 (representing high amounts) and 300 mg kg -1 (serving as a model for honey from sides with massive occurrence of PA-plants and honey harvesting by comb pressing which might contain perga and would therefore result in a unusual high PA-pollen load of the end product).…”

“…whether pollen from PA-plants is the only source of PA-contamination of honey (Boppré et al 2005;Boppré et al 2008;Kempf et al 2010a;Kempf et al 2010b). This scenario would, at least to some degree, offer the possibility that legally permitted filtration of PA-pollen containing honey could result in a significant lower PA-content of the filtered honey.…”