Antioxidant and antimicrobial properties of propolis extracts from four ecological zones of Uganda: its potential application in livestock health.

Abstract

Propolis, a resinous bee product has been attracting global interest from the scientific community due to growing scientific evidence of its beneficial biological properties. While studies elsewhere document evidence of propolis action on diseases, evidence on the performance of Ugandan propolis remains lacking. This has led to less income contribution from bee keeping to rural livelihoods due to limited product diversity within the local market in Uganda. It is for this reason that this study investigated the colour, total phenol content, antioxidant, and antimicrobial properties of propolis extracts from four ecological zones of Uganda. This study involved preparation of eight crude propolis extracts from the raw propolis collected from Lira, Soroti, Bunyangabo and Karamoja, by cold maceration method using ethanol and methanol solvent. Four colours of Ugandan propolis extracts were identified that is black, brown, orange and yellow. Methanol extracts had a higher yield of extraction (17.25 percent) than ethanol extracts (16.30 percent). The total phenol content of the extracts was determined spectrophotometrically by Folin–Ciocalteau method. Methanol extracts had higher phenolic compounds (73.23 mg GAE/g) than the ethanol extracts (39.95 mg GAE/g). The antioxidant properties (the free radical scavenging activity) of the propolis extracts were assayed using DPPH free radical assay. The antioxidant properties reported were generally low and ranged from 8.76 to 34.53 percent. Antimicrobial activity was tested against Gram negative bacteria that is Avian Pathogenic Escherichia coli (APEC); isolated from active cases of colibacillosis among chicken, Staphylococcus aureus; (ATCC 25923) and Aspergillus niger; isolated from chicken feed. Sensitivity testing was done using the agar well diffusion method and Minimum Inhibitory Concentration (MIC) was determined using broth dilution susceptibility test. Staphylococcus aureus was sensitive to all the analysed propolis extracts while APEC and Aspergillus niger were not. The activity of propolis against Staphylococcus aureus means that it has the potential for application in prevention and control of livestock diseases caused by this bacteria. However, there is need for further screening of the various colours of propolis collected at different seasons and to determine the components responsible for activity against Staph aureus. This will form basis for possible formulation and quality control of antimicrobial products from the extracts for further in vivo trials. The study recommends investigating level of contamination of propolis with heavy metals, effect of storage and handling on the physio-chemical properties of Ugandan propolis.