ANTIMICROBIAL ACTIVITIES AND PHYTOCHEMICAL CONTENTS OF SUB-TERENEAN NESTING STINGLESS BEE PRODUCTS FROM BARINGO COUNTY

Abstract

In Baringo County, stingless bee honey is traditionally used to treat various ailments commonly associated with bacterial and fungal infections. However, there is limited experimental data on antimicrobial activities and phytochemical contents of stingless bee products from Baringo County. The objectives of this study were to evaluate the in vitro antimicrobial activities and phytochemical contents of honey and pollen from stingless bees Meliponula beccarii and Plebeina hildebrandti from Baringo County. Eighteen honey and thirteen pollen samples were conveniently sampled from eighteen wild occurring stingless bee nests in three different ecological zones of Baringo County and used for analysis. The study adopted a factorial experimental design, whereby three increasing concentrations of honey and pollen samples were prepared and tested against E.coli, H.influenzae, MRSA and C. albicans using agar well diffusion bioassay. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentration (MBCs) were measured using broth microdilution assay. Phytochemical screening was done qualitatively using standard methods. Data was analysed using Graphpad Prism software version 7 employing two-way Analysis of Variance and Tukey’s post-hoc tests. M.beccarii honey samples showed significantly higher mean zones of inhibition against E. coli ( p<0.0001, N=11), H. influenzae (p<0.0001, N=11), and MRSA (p>0.0001, N=11) at 100% v/v compared to distilled water but significantly lower mean zones of inhibition against H. influenzae (p<0.0001, N=11), E. coli (p<0.0001, N=11) and MRSA (8.1±2.8 mm vs 27±0 mm) in comparison to ciprofloxacin. The mean MICs were 9.38% (v/v), 18.75% (v/v) and 18.75% (v/v), against E. coli, H. influenzae and MRSA respectively. M. beccarii honey was bactericidal only against MRSA with a mean MBC of 60.94% (v/v). P. hildebrandti honey samples in comparison to distilled water, had significantly higher mean zones of inhibition at 100% v/v against E. coli (12.1±2.01 mm vs 0 mm, p<0.0001, N=7), H. influenzae (10.1±4.8 mm vs 0 mm, p<0.0001, N=7), and MRSA (14.5±2.4 mm vs 0 mm, p>0.0001, N=7), but significantly lower mean zones of inhibition against H. influenzae (9.0±1.05 mm vs 25±2.0 mm, p<0.0001, N=7), E. coli (10.9±1.1 mm vs 30.26±0.8 mm, p<0.0001, N=7) and MRSA (12.8±1.8 mm vs 26±0.7mm ) in comparison to ciprofloxacin. The mean MICs of 13.75 % (v/v), 13.75% (v/v) and 17.71% (v/v), were exhibited against E. coli, H. influenzae and MRSA respectively and was bactericidal against E. coli, H. influenzae and MRSA with mean MBC of 22.5 (v/v), 25% (v/v) and 28% (v/v) respectively. None of the honeys from the two species tested showed activity against C. albicans even at 100% v/v. All pollen samples had no antimicrobial activities. Phytochemical analysis revealed the presence of tannins, alkaloids, saponins, triterpenoids, phenols, flavonoids, steroids and glycosides but not terpenoids in all the honey and pollen of M. beccarii and only two of P. hildebrandti. Five P.hildebrandti honey and pollen lacked phenols. Therefore, most but not all honey samples of stingless bees M. beccarii and P. hildebrandti in Baringo County have antibacterial activities. The samples of pollen and honeys contain a range of valuable phytochemicals. Study confirmed the ethnomedicinal antibacterial uses of M. beccarii and P. hildebrandti honey and recommends in vivo studies and clinical trials.