Characterization of the nematicidal activity of natural honey

Antimicrobial activities of honey against bacteria and fungi are extensively reported in the scientific literature. However, its nematicidal potential has not been characterized so far. This study examined the effect of natural honey on model nematode Caenorhabditis elegans and analyzed the honey component(s) responsible for nematicidal activity. Characterization of honey-treated C. elegans was done using fluorescence and phase contrast microscopy. Egg-laying and egg-hatching defects of honey-treated C. elegans were studied. For identification of nematicidal component(s), bioactivity-directed fractionation of honey samples was carried out using dialysis, ultrafiltration, chromatographic, and spectroscopic techniques. Natural honeys of different floral sources showed nematicidal activity against different developmental stages of C. elegans. The nematicidal components of honey induced cell death in intestinal lumen and gonads of C. elegans as revealed by microscopy. The nematicidal action of honey was found to be due to reproductive anomaly as manifested by defects in egg-laying and -hatching by C. elegans. Honey with concentration as low as 0.03% exerted profound egg-laying defects, whereas 6% honey showed defects in egg hatching. The major sugar components of honey were not involved in observed nematicidal activity. The bioactive components responsible for anti-C. elegans activity were found in the 2-10 kDa fraction of honey, which was resolved into ∼25 peaks by reverse phase HPLC. LC-MS followed by further spectroscopic characterization revealed a glycoconjugate with the molecular mass of 5511 as the major nematicidal component of honey.