Dual Antibacterial and Immunostimulatory Effects of Green Tea Extract in Drosophila melanogaster

Abstract

Bacteria resistant to antibiotics are a major threat to the world community. To overcome this serious problem, discovering new antibacterial agents through the exploration of various potential sources is very important, one of which is using natural ingredients. This study was conducted aiming to determine the in vivo antibacterial and immunostimulant activities of green tea extract (GTE) (Camellia sinensis) in the Drosophila melanogaster larval infection model. Green tea was extracted using n-hexane and 50% ethanol by a multilevel extraction method. Assessments for GTE toxicity as well as its effect on the survival and the modulation of gene expression in D. melanogaster, were carried out. The results showed that the administration of GTE was relatively safe for D. melanogaster larvae. Furthermore, the administration of GTE to the wildtype Oregon R line of D. melanogaster experienced an improved survival rate after being infected with Staphylococcus aureus, suggesting that GTE may provide antibacterial protection against S. aureus. A similar phenotypical observation, improvement in the survival rate upon S. aureus infection, was evident in the immunodeficient mutant larvae that were treated with GTE. In addition, gene expression analysis demonstrated increased expression of Drs, an antimicrobial peptide produced by D. melanogaster in response to infection by S. aureus, a Gram-positive bacteria. This result indicates the prospective immunostimulatory activity of GTE in D. melanogaster. Taken together, our phenotypic and molecular analysis revealed the dual immunostimulatory and antibacterial activities of GTE against S. aureus in a Drosophila larval infection model.

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