Bactericidal activity of quercetin like-compounds isolated from Dendrophthoe petandra leaves against Salmonella spp. and Escherichia coli: an in vitro experimental study

Background: Dendrophthoe pentandra L., Miq, a type of mistletoe that grows abundantly on Lansium domesticum, is estimated to possess antimicrobial activity against bacteria. This study focused on extracts of the plant, particularly quercetin-like compounds (QLC), with the aim of identifying potential analyte compounds as new antibiotics. The leaves of the mistletoe plant underwent methanol-ethyl acetate-n-hexane maceration, followed by QLC extraction using preparative high-performance liquid chromatography equipment. The extracts were subsequently analyzed using ultra-performance liquid chromatography-tandem mass spectrometry, Fourier transform infrared spectrophotometry, and proton analysis via nuclear magnetic resonance spectroscopy. The QLC extracts, ranging from 500 ppm to 10,000 ppm, were tested for antimicrobial activity against Salmonella species and Escherichia coli in vitro, based on colony growth inhibition screening. The results were further analyzed using probit analysis to determine the bactericidal values against these two enterobacteria.Results: The findings indicated that the minimum inhibitory concentration required for 50% mortality of Salmonella species colonies was 359.283 μg/mL and that a 75% reduction occurred at an exposure of 1.6 mg/mL of QLC. Additionally, a 99% colony death rate was observed at a minimum bactericidal concentration of 61.9 mg/mL of QLC. In contrast, exposure to QLCs did not exhibit any colony-inhibiting or bactericidal effects on Escherichia coli.Conclusions: The QLCs extracted from the leaves of Dendrophthoe pentandra growing on the host plant Lansium domesticum demonstrate significant potential for development as new antibiotics against Salmonella species. However, they are not recommended for use against Escherichia coli (P