Evaluation of Phenolic Compounds in Cistus creticus Bee Pollen from Greece. Antioxidant and Antimicrobial Properties

Abstract

This study was carried out to evaluate the antioxidant properties of Greek endemic Cistus creticus L. (rock rose) bee pollen and define its phenolic compounds. In the framework of our scientific studies on Greek bee keeping products, we report herein our research on three Greek bee pollen samples from Cistus. Their pollinic spectra were obtained by Louveaux's quantitative microscopical analysis and it showed that one of them had Cistus sp. (Cistaceae) as abundant pollen (together with low percentage of Brassica sp. (Cruciferae). Throughout the chemical analysis of the extracts, several secondary metabolites of flavonoid structure have been identified as major components. Specifically, quercetin-7-rhamnoside (1), quercetin-3-neohesperidoside (2), kaempferol-3-neohesperidoside (3), myricetin-3-neohesperidoside (4), kaempferol-3-glucoside (5) and quercetin-3-glucoside (6) have been isolated and their structures were elucidated on the basis of spectral evidence. Moreover, the total phenolic and flavonoid content was estimated and the free radical scavenging activity was determined by DPPH and ABTS assays. The antimicrobial activity of the extracts was tested against six Gram-positive and -negative bacteria and three pathogenic fungi, and the butanol extract showed a very interesting broad antimicrobial profile (MIC 1.98•10−3 - 2.98•10−3 mg/ml) against all the assayed microorganisms.