Honey is a complex natural bee product, produced by processing of nectar and excretions of insects. It consists of water, various sugars, proteins, organic acids, minerals and trace metals. The latter could be utilized for environmental monitoring, as environmental pollution can be monitored by determining the concentration of heavy metals in honey. Smaller quantities of peptides are also present in honey, which through their antimicrobial and anti-inflammatory action contribute to the pharmacological activity of honey. They are mostly peptides of animal origin, particularly excrements of bee hypopharyngeal glands, which process the raw honey.
In order to establish useful models for determining the botanical source of honey and its usefulness for environmental monitoring, different honey samples were analysed with optical inductive coupled plasma emission spectrometry (ICP-OES). With the use of statistical analyses, we determined the variance between the concentrations of different elements in terms of geographical and botanical origin. Based on the results obtained, we tried to find a link between the content of heavy metals and environmental pollution. The content of various elements, especially heavy metals, can serve not only as a botanical and authenticy marker, but also as an indicator for environmental monitoring.
To study peptides in honey, their separation and visualization are important. We focused on peptides below the size of 10 kDa and optimized a new protocol for SDS-PAGE since the classic glycine-based buffer system is not suitable. With tricine-SDS-PAGE we successfully separated two bands of peptides with apparent molecular masses of 5 kDa and 7 kDa and visualized them with silver staining. The peptide band of 5 kDa likely corresponds to defensin-1 and/or apisimin according to literature. Because the detection limit of Coomassie Brilliant Blue staining is insufficient for visualization of peptides with low concentrations, we also optimized the staining process using staining with silver nitrate. The results were quantified using QuantityOne software (Bio-Rad, ZDA) and royal jelly as control, since it is rich in protein and contains a high content of defensin-1. The concentrations of separated peptides were calculated by referencing royal jelly with a known concentration of defensin-1 peptide. The results showed the presence of the 5 kDa peptide band in the royal jelly sample, but no 7 kDa peptide band. In honey, the 7 kDa band was stronger than the 5 kDa peptide band, which was present only in small amounts. Both peptide bands were present in samples independently of botanic or geographic origin with no statistically significant differences between them.
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