Blog 2: Correlating the flavonoid and phenol content to the antioxidant activity of various European propolis

Over the past months, the main progress made has been the preparation and testing of the individual samples of propolis from England, Greece, Portugal, Russia, Latvia, Serbia, Hungary, Bulgaria, and Lithuania. The preparation of the samples involved creating an extract through sonication of the propolis in ethanol and subsequent filtration. One unexpected outcome was that some of the samples, after sonication, had hardened into a thick, paste-like mixture. The samples only required additional heat to ultimately be filtered to prepare extracts, though it was interesting that only some samples displayed this feature. We assume that this characteristic of the unique samples is a product of differences in the additional components of propolis such as beeswax, which we were intending on removing as part of preparing the extract.

Once all the samples’ extracts were prepared, we began performing the different assays to measure the antioxidant activity, phenolic content, and flavonoid content. Each assay needs to be performed several times to ensure that the data collected is accurate. For each assay, we tested serial dilutions of each sample extract to more accurately quantify the extent to which the reagents of the assay interact with the compounds in the extracts. Moving forward, more assays will be done to ensure accurate data and then the data obtained can be analyzed to look for trends and relationships.

Blog 1: Correlating the flavonoid and phenol content to the antioxidant activity of various European propolis

The subject of my research is the analysis and correlation of the antioxidant activity, phenolic content, and flavonoid content of bee propolis from several regions of Europe. Bee propolis is a sticky, resinous substance, composed of botanical exudate, pollen, resin, and wax, among other variable substances, each in varying amounts. Known for having many potential health benefits, propolis has been shown to have anti-oxidative, anti-inflammatory, and antimicrobial properties1. The various functionalities of propolis are a result of the wide diversity of chemicals and molecules that are found in it. The phenolics and flavonoids that are present in a given sample of propolis are the compounds that give propolis its anti-oxidative properties, which is why this study will look at how these properties are related to each other. The unique and individual properties of propolis are widely varied as factors such as the region, species of bee, season of collection, and variance of botanical source used by the bee will result in distinctive differences between samples2. The study of these properties will provide insight to the usefulness of propolis as a natural and complementary medicine.

In this study, samples from England, Greece, Portugal, Russia, Latvia, Serbia, Hungary, Bulgaria and Lithuania were used. For each sample, extracts were prepared for analysis. The antioxidant activity and ability will be tested with assays such as the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) free radical scavenging assay, the 2,20-azinobis-(3-ethylbenzothiazoline- 6-sulfonic acid) diammonium salt (ABTS) assay, and Ferric Reducing Antioxidant Power (FRAP) assay. The phenolic content of each sample is measured using Folin-Ciocalteu method and the flavonoid content will be measured by the AlCl3 colorimetric method. Each of these assays involve the interaction of particular compounds in a sample with a reagent that produces a measurable colorimetric change. The results of these assays will be compared within and between different samples to indicate the properties of a particular sample of propolis as well as to allow the comparison of the different samples.

(1)       Kocot, J.; Kiełczykowska, M.; Luchowska-Kocot, D.; Kurzepa, J.; Musik, I. Antioxidant Potential of Propolis, Bee Pollen, and Royal Jelly: Possible Medical Application. Oxid Med Cell Longev2018, 2018. https://doi.org/10.1155/2018/7074209.

(2)       Bankova, V. S.; Castro, S. L. de; Marcucci, M. C. Propolis: Recent Advances in Chemistry and Plant Origin. Apidologie2000, 31(1), 3–15. https://doi.org/10.1051/apido:2000102.