Chemical and functional characterisation of propolis collected from East Andalusia (southern Spain)

Propolis is a complex mixture of natural sticky, gummy and resinous components produced by honeybees (Apis mellifera L.) from plant materials. However, phytochemical data of the Andalusian (southern Spain) propolis are scant.

The primary objectives of this study were to chemically characterise the compounds and evaluate the anti-oxidant activity found in 28 Andalusian propolis samples.

Ethanol extracts of propolis (EEP) were prepared and examined for their anti-oxidant activity by 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) and 2,2-diphenyl-1-picrylhydrazyl assays. To characterise the phenolic composition, the presence of 11 compounds was identified by HPLC analysis with photodiode array and mass spectrometric detection.

All propolis samples had strong anti-oxidant activity, accompanied by high total phenolic content. The most abundant compounds were flavonoids. Concerning the phenolic compounds content, our results showed that the 75% of the samples analysed contained at least 80 mg/g of flavonoids, primarily pinobanksin 3-acetate, pinocembrin, chrysin, galangin and pinobanksin. Caffeic acid phenethyl ester was detected in almost all EEP samples but in smaller proportions (mean 12.9 ± 2.8 mg/g).

The present investigation constitutes the first comprehensive report on the phenolics identified in southern Spanish propolis. The results revealed that the samples tested showed a high scavenging activity and therefore indicate the possible use of Andalusian propolis as an important source of natural anti-oxidants.