Detection and Quantification of Pyrrolizidine Alkaloids in Antibacterial Medical Honeys

Abstract

In recent years, there has been an increasing interest in antibacterial honey for wound care ranging from minor abrasions and burns to leg ulcers and surgical wounds. On the other hand, several recent studies demonstrated that honey for human consumption was contaminated with natural occurring, plant derived pyrrolizidine alkaloids.1,2-Unsaturated pyrrolizidine alkaloids are a group of secondary plant metabolites that show developmental, hepato-, and geno-toxicity as well as carcinogenic effects in animal models and in in vitro test systems. Hence, it was of particular interest to analyze the pyrrolizidine alkaloid content of medical honeys intended for wound care.19 different medical honey samples and/or batches were analyzed by applying a recently established pyrrolizidine alkaloid sum parameter method. 1,2-Unsaturated pyrrolizidine alkaloids were converted into the common necin backbone structures and were analyzed and quantified by GC-MS in the selected ion monitoring mode.All but one medical honey analyzed were pyrrolizidine alkaloid positive. The results ranged from 10.6 µg retronecine equivalents per kg to 494.5 µg retronecine equivalents/kg medical honey. The average pyrrolizidine alkaloid content of all positive samples was 83.6 µg retronecine equivalents/kg medical honey (average of all samples was 79.3 µg retronecine equivalents/kg medical honey). The limit of detection was 2.0 µg retronecine equivalents/kg medical honey, while the limit of quantification was 6.0 µg retronecine equivalents/kg medical honey (S/N > 7/1).Based on the data presented here and considering the fact that medical honeys can be applied to open wounds, it seems reasonable to discuss the monitoring of 1,2-unsaturated pyrrolizidine alkaloids in honey intended for wound treatment.

Determination of Pyrrolizidine Alkaloids in Honey with Sensitive Gas Chromatography-Mass Spectrometry Method

“…This low LOQ could be achieved due to use of the new elution mixture consisting of ethyl acetate, methanol, ammonia, and triethylamine (8:2:0.1:0.1). The obtained LOQ is significantly lower than that reported by Kempf et al (2008) and Cramer and Beuerle (2012) which were 10 μg kg −1 and 6 μg retronecine equivalent kg −1…”

“…Gas chromatographic methods have been popular for analysis of PAs in plants, in which alkaloid concentrations are much higher (Stelljes et al 1991;Witte et al 1993). However, GC-MS can also be a useful technique for an analysis of honey samples for the presence of 1,2-unsaturated PAs, especially when the sum parameter approach is used (Kempf et al 2008, Cramer andBeuerle 2012). The advantage of this approach is that the content of the present 1,2-unsaturated PAs is converted into the common backbone structures (Fig.…”

“…As pyrrolizidine alkaloids are polar compounds for dilution of honey samples, 0.05 M sulfuric acid has been mostly used (Kempf et al 2008;Cramer and Beuerle 2012;Griffin et al 2013); only in one study 0.5 M sulfuric acid was applied (Orantes-Bermejo et al 2013). However, in a previously conducted study, 1 M hydrochloric acid was chosen as the most effective extraction solvent of PAs from feed materials (Kowalczyk and Kwiatek 2017); for this reason, HCl solutions were also tested for honey matrix.…”

“…Only two methods based on gas chromatography-mass spectrometry (GC-MS) for the determination of PAs in honey have been described in the literature (Kempf et al 2008;Cramer and Beuerle 2012). The approach used in GC-MS analysis involves the reduction of 1,2-unsaturated PAs to their respective necine base backbone structures: retronecine and heliotridine.…”

Incidence of Pyrrolizidine Alkaloids in Herbal Medicines from German Retail Markets: Risk Assessments and Implications to Consumers

“…The occurrence of potentially toxic pyrrolizidine alkaloids (PAs) in non-PA plants containing HMs is currently intensely being discussed in Europe and addressed by regulatory bodies and producer associations (European Medicines Agency (EMA), 2016;Steinhoff, 2017). Most recently, PAs have been detected in Hypericum perforatum products (Mulder, López-Sánchez, These, Preiss-Weigert, & Castellari, 2015), antibacterial medical honeys (Cramer & Beuerle, 2012), or in herbal teas for babies, pregnant, or lactating women (Mädge et al, 2015) and have raised concerns about the safety of HMs in Europe. Even though H. perforatum per se does not naturally produce PAs, it has however been implicated in frequently contaminating herbal medicinal products with these toxic alkaloids.…”