Phenolic Content, Antimicrobial and Antioxidant Activities of Two Types of Saudi Entire Honey and their Extracts

Abstract

Honey is not only considered as a food or sweetener, its consumption has long been regarded as having beneficial effects on human health. This study aimed to investigate the chemical constituents, antimicrobial and antioxidant activities of natural Saudi Sidr and Talh honeys. Fresh samples of Sidr and Talh honeys were obtained from apiaries in Riyadh, Kingdom of Saudi Arabia (KSA). Beside entire honey samples; ethyl acetate, ethanol and water extracts were prepared using standard procedures. Antimicrobial activity was determined against Gram negative and Gram positive bacteria as well as two fungi species using the disc diffusion and microdilution methods. Phytochemical screening was performed by thin layer chromatographic (TLC) technique. Total phenolic contents were determined colorimetrcially. Antioxidant activity was evaluated by examining the capacity of honey samples to scavenge free radicals, reduce ions and chelate iron metal. Results of antimicrobial activity showed that entire honey exerted higher antimicrobial activity than extracts. Sidr honey was more effective against Bacillus subtilis, Staphylococcus aureus and Escherichia coli with minimum inhibitory concentration ((MIC) value of 3.125 μg/mL. Talh honey was more active against Pseudomonas aeruginosa and Candida albicans (MIC = 3.125 μg/mL). All honey samples (except ethanol extract of Sidr honey) exerted higher anti-2,2 0-Azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical activity than their capacity to scavenge the 2, 2-diphenyl-1- picrylhydrazyl (DPPH) free radicals. All samples had considerable metal reducing capacity with higher activity to reduce Cu++ to Cu+ than Fe +++ to Fe++. The total antioxidant activity of both types of honey, from the phosphomolybdenum assay, was not significantly (p ≥ 0.05) different. In most assays the ethyl acetate extract from the two honeys exerted significantly (p ˂ 0.05) the highest activity. Both honeys and their extracts did not reveal any chelating activity. TLC showed that the two honey types were rich in phenols. The total polyphenolic content of the Sidr and Talh honeys and their extracts was in the range of 2.86 - 7.21 and 3.80 - 17.33 mg gallic acid equivalents/g respectively and the total flavonoids content was in the range of 0.05 - 1.17 and 0.18 – 2.38 mg rutin equivalents/g respectively. Highest values were obtained from the ethyl acetate extract. In conclusion, the studied Saudi Sidr and Talh honeys may have a great potential as antioxidant and antimicrobial sources for pharmaceutical and cosmetic applications.