Antimicrobial Activities And Physico-chemical Analyses Of Honeys

Honey has been used traditionally for ages to treat infectious diseases. Antimicrobial activity of honey is complex due to the involvement of multiple bioactive compounds. The physico-chemical and antimicrobial properties of honey varieties from Apis mellifera and stingless bees, Hypotrigona sp. (Okotobo - Igbo) and  Melipona  sp.  (Ifufu - Igbo) were studied using International Honey Commission protocols and microbiological methods (agar-well diffusion and broth microdilution) respectively. A total of nine honey samples (3 from each) were used. The  physico-chemical analyses  of the honey varieties showed that the honeys had mean pH range of 3.73±0.08 - 4.24±0.20. Honey samples from Hypotrigona sp. had the  highest  mean  moisture (17.50 ± 0.80 %), total dissolved solids (370.01 ± 22.51 ppm), hydromethylfurfural (16.58  ±  0.37  mg/kg),  total  acidity  (35.57  ± 0.42meq/kg),  protein  content  (16.58 ± 0.37 g/kg) and phenol content (527.41 ± 3.60 mg/kg). Melipona sp. honey had the highest average flavonoids (86.39 ± 4.69 mg/kg), total sugar (80.71 ± 1.37 % (g/100g) and reducing sugar (75.64 ± 1.99 % (g/100g) contents.

There were no statistically significant differences between the mean pH, electrical conductivity and protein contents of A. mellifera and Melipona sp. honeys (p<  0.05).  Several  strong correlations were observed among some of the physicochemical properties of these honey varieties. In the initial antimicrobial activity testing, Hypotrigona sp. honey samples had statistically the highest mean inhibition zones diameter  (mm)  against MDR Staphylococcus aureus (7.14 ± 4.11), Klebsiella pneumonia (7.92 ± 3.96), Pseudomonas aeruginosa ATCC 25783 (9.77 ±4.58), MDR S. enterica (6.96 ± 4.03), and Aspergillus niger (10.12 ± 5.51).The  minimum inhibitory concentrations (MICs)  of the honey varieties from A. mellifera, Hypotrigona sp. and  Melipona sp.  ranged from 6.3 – 25.0%, 3.1 – 12.5% and 6.3 – 25.0% (v/v) respectively. There were no statistically significant differences between the mean MICs of A. mellifera,  Hypotrigona sp. and Melipona sp.honeys against P. aeruginosa ATCC 25783 (7.64 ± 2.76, 7.28 ± 4.14 and 8.33 ± 3.31 % v/v respectively).Hypotrigona sp. honey had the least mean MICs (4.15 ± 1.58 – 11.11 ± 2.76 % v/v) against most of the test organisms.The minimum biocidal concentration (MBC) of the honey varieties fromA. mellifera, Hypotrigona sp. and Melipona sp. against the test organismsvaried from 6.3 – 50%, 3.1 – 25% and 12 – 50% (v/v) respectively. There were no statistically significant differences between the mean MBCs of the honey varieties against Klebsiella pneumonia(p = 0.669),P.  aeruginosa ATCC  25783 (p =  0.977),  A.  niger(p

= 0.688) and C. albicans (p = 0.168).The honey varieties had exceptional levels of hydrogen peroxide-dependent activity, and non-peroxide activity against the test organisms.  This research has also shown that the honey  varieties varied significantly  in their physicochemical and antimicrobial properties. ‘Okotobo’ and ‘ifufu’ honeys  that are both not consumed as widely as regular bee honeyhave shownto contain bioactive compounds and have antimicrobial properties similar to those of regular bee honey.