Physico-chemical, antioxidant and anti-microbial properties of some Ethiopian mono-floral honeys

Honey has been widely used to treat several human pathogens. However, all honeys may not have equal potencies against different human pathogens. The purpose of the current work was to investigate the physico-chemical and antimicrobial qualities of some mono-floral honeys from Ethiopia against some human pathogen bacteria and fungi. In the study, seven different botanical origin honeys were used of which some were from plants known for their medicinal properties. The samples were tested for their major physico-chemical properties (sugar profiles, total free acids, pH, color, electric conductivity and total soluble substances) and their medicinal values as total antioxidant capacity, total phenolic content and antimicrobial properties as minimum inhibitory concentration against some human pathogens, following standard protocols. Generally, the average values of the physico-chemical properties of the samples were within the acceptable ranges of world honey quality values. The average total antioxidant value of the samples was 320.3 ± 15.1 with range of 225.4 ± 12.8-465.7 ± 21.8 μM Fe(II)/100g. Relatively higher values 421.5 ± 23.4 and 465.7 ± 21.8μM Fe(II)/100g recorded for Croton macrostachyus and Vernonia amygalina honeys respectively. The average phenolic contents of the samples varied from 233.3 ± 24.0 to 693.3 ± 26.8 mgGAE/kg and relatively higher values recorded for C. macrostachys and V. amygdalina honeys. The significant proportion of the tested samples showed strong antimicrobial qualities inhibiting the growth of tested pathogens at concentration of 10.5%-28.6% of MIC (% v/v). Honeys from medicinal plants (C. macrostachys and V. amygdalina) relatively showed more antimicrobial properties which could be due to the presence of plant specific phytochemicals which require further investigations.

Keywords: Antimicrobial properties; Antioxidant; Medicinal plants; Mono-floral honeys; Phenolic compounds.