Promising antimicrobial activity against the honey bee parasite Nosema ceranae by methanolic extracts from Chilean native plants and propolis

Abstract

The gut parasite Nosema ceranae is one of the most prevalent honey bee microsporidia worldwide and its chemical management in American countries is mainly based on the antibiotic fumagillin. However, it has recently been reported that this drug has negative side effects in honey bees; therefore, non-harmful alternative treatments must be found. The effects of methanolic extracts (2, 4, 8 and 16%) from Chilean native plant leaves (Aristotelia chilensis, Ugni molinae, and Gevuina avellana) and propolis (Biobío (BB) and Los Ríos (LR) regions) on N. ceranae load, diet consumption and the survival of N. ceranae-infected honey bees were evaluated through oral intake. When bees were N. ceranae-infected and treated with extracts of A. chilensis (8%), U. molinae (2 and 8%) and propolis BB (8%) simultaneously, the N. ceranae load decreased significantly and the survival of infected bees also improved. On the other hand, when bees were first extracts-treated and then N. ceranae-infected, their diet consumption increased and all extracts significantly decreased the N. ceranae load in infected bees. However, only extracts from U. molinae (2 and 8%) and propolis LR (8%) maintained a higher survival rate in infected bees. Natural compounds were also identified; U. molinae and A. chilensis leaves had high concentrations of rutin and myricetin, whereas galangin and pinocembrin were found mostly in southern Chilean propolis (LR). This study constitutes the first report of the antiparasitic activity of propolis against N. ceranae in Apis mellifera and the antimicrobial activity of Chilean plant extracts against this honey bee parasite.