Evaluation of radical scavenging capacity of polyphenols found in natural malaysian honeys by voltammetric techniques

Abstract

As minor constituents present in natural honey, polyphenols have the capacity as antioxidant by donating electron to halt detrimental actions of free radicals. The present work aims to analyze the electrochemical behaviour of polyphenols identified in Malaysian Apis and Trigona honey samples, determine and compare their reducing strengths as well as qualitatively evaluate the radical scavenging capacity of these phenolics in Malaysian honey samples. Six flavonoids, eight phenolic acids, and tannin pentagalloyl glucose (PGG) dissolved in 0.1 M PBS pH 7 were studied by cyclic voltammetry (CV). Seventeen Malaysian honey samples were analyzed using differential pulse voltammetry (DPV). Cyclic voltammograms revealed that polyphenols with catechol moiety in their structure exhibited Ep1a at low potentials, ranging between +0.173 V and +0.404 V. PGG and quercetin may have equal tendency to donate electron (same Ep1a) but higher peak current was observed for the former indicates its higher reducing strength, suggesting PGG as the strongest antioxidant among studied polyphenols. From DP voltammograms, oxidation of honey phenolics occurred in all honey samples with predominant catechol-bearing peak P1 observed in nanas N1, kelulut K3 and tualang T1 honeys. The varied peak current intensities observed for P1-P3 in all analyzed Malaysian honey samples suggested that these honey samples can act against free radicals at varying degree and thus are good sources of natural antioxidants.