Abstract
Aim of study: To evaluate the antimicrobial activity of the hexanic extract (HE) of Achyrocline satureioides on Paenibacillus larvae - a gram-positive spore-forming bacillus that affects the larval stage and causes American Foulbrood (AFB) - and its oral and contact toxicity on larvae and adult honey bees.Area of study: A. satureioides plants were collected in Santa Monica (32° 05’ 29” S, 64° 36’ 54” W, Córdoba. Argentina). The larvae and adults of Apis mellifera were obtained from the experimental apiary of the University of Córdoba, Spain.Material and methods: P. larvae 9 was previously isolated and identified in the Laboratory of General Microbiology (Dept. of Microbiology, National University of Río Cuarto, Argentina). The HE was obtained by liquid-liquid extraction. The minimum inhibitory concentration (MIC) of HE was determined by a microdilution method. This concentration and 2 ½ MIC were used for in vitro toxicity tests. Oral toxicity was tested on larvae, feeding them with both concentrations of the HE, while on adult bees the HE was spread to determine contact toxicity.Main results: The HE showed antimicrobial activity, the MIC obtained was 0.4 μg/mL. The HE presented very low toxicity at the MIC and 2 ½ MIC, with survival percentages to be around 95% for adult bees and larvae.Research highlights: The results show that this extract could be used for the development of an alternative product for a safe and effective treatment of AFB.
Highlights
The honeybee, Apis mellifera, is a social insect living in a colony or a hive comprising between 40 to 80 thousands individuals
The Asteraceae family is rich in phenolic compounds (Emerenciano et al, 2001; Heiden et al, 2007; Katinas et al, 2007) and A. satureioides, a member of this family, has been reported as one of the species with higher flavonoid content like others such as Ginkgo biloba and Epilobium parviflorum (Arredondo et al, 2004)
A qualitative assay of the hexanic extract (HE) of this plant was analyzed and the results showed that flavonoids were present as it was reported by other authors who studied the chemical composition of A. satureioides extracts and considered them as an interesting source of flavonoids, regardless of whether the extraction was performed with polar or nonpolar solvents (De Souza et al, 2007; Fachinetto et al, 2007; Santin et al, 2010)
Summary
The honeybee, Apis mellifera, is a social insect living in a colony or a hive comprising between 40 to 80 thousands individuals. Honeybees are recognized to have an essential role in nature for their efficient abilities as pollinators, considering that they pollinate more than one third of human crops, contributing to the cross-pollination of many fruits and forages (Watson & Stallins, 2016). Products such as propolis, royal jelly and bee wax, which are used by humans for several purposes. They are very important for mankind survival. Like all living organisms, honeybees can be altered with diseases and pests
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