Abstract:
Over the past decades, honeybees have been on the decline which is brought on by many causes such as pests, microorganisms, etc. A significant pest of the honeybees includes the Varroa mite. This worldwide pest can cause severe damage to honeybees or cause destruction of bee colonies by spreading pathogenic microorganisms and devouring their host’s nutrients. Previous studies have shown that a way to control Varroa is through the use of plants that express bioactive properties. Such botanical species include the Vitex lucens, also is known as Puriri. Puriri is a tree that is an endemic and native species to New Zealand, which is listed in the Rongoa Māori or the Medical Native Plants of New Zealand. It has historically been used to treat pain in different areas of the body, improve blood and nutritional flow throughout, as well as having an antibacterial characteristic. In this study, puriri leaves were extracted using several solvents (water, ethanol and cyclohexane). A novel technique of using ultrasound was also applied for improving the aqueous extraction yield. The extracts of puriri leaves were investigated for their bioactive properties which can be used for Varroa control. The antioxidant activity was determined by three assays including total phenolic contents (TPC) assay, DPPH assay and ABTS assay. All extracts (water extract with the process of maceration, ultrasound and reflux, water extract with maceration alone, ethanol extract and lipid extract) presented antioxidant properties and high TPC value. The antimicrobial activity test was performed using the disc diffusion method and modified dilution method against bacteria such as Pseudomonas fluorescens, Enterococcus faecalis, Bacillus subtilis, Bacillus cereus, Enterobacter aerogenes, S. epidermidis and Escherichia coli. All puriri leaves extracts had a variable degree of antimicrobial activity against bacteria related to honeybee or Varroa. B. cereus also known as a food-borne pathogen, was found to be the most susceptible to all of the puriri leaves extracts. The antioxidant and antimicrobial properties of the puriri leaves extracts determined in this study offer the direction of developing the anti-Varroa products for the honeybee industry in the future.