title: Lupinifolin from Derris reticulata possesses bactericidal activity on Staphylococcus aureus by disrupting bacterial cell membrane.
abstract: In this study, lupinifolin, a prenylated flavonoid, was isolated from Derris reticulata stem, identified by NMR spectra and confirmed with mass spectrometry. Lupinifolin was freshly prepared by solubilizing in 0.1 N NaOH and immediately diluted in Müller-Hinton broth for antibacterial testing. The data showed that Gram-positive bacteria were more susceptible to lupinifolin than Gram-negative bacteria. Of four strains of Gram-positive bacteria tested, Staphylococcus aureus was the most susceptible. Using the two-fold microdilution method, it was found that lupinifolin possessed antimicrobial activity against S. aureus with minimum inhibitory concentration and minimum bactericidal concentration of 8 and 16 µg/ml, respectively, which is less potent than ampicillin. However, from the time-effect relationship, it was shown that lupinifolin had faster onset than ampicillin. The faster onset of lupinifolin was confirmed by scanning electron microscopy. To investigate the mechanism of action of lupinifolin, transmission electron microscopy (TEM) was performed to observe the ultrastructure of S. aureus. The TEM images showed that lupinifolin ruptured the bacterial cell membrane and cell wall. Due to its fast onset, it is suggested that the action of lupinifolin is likely to be the direct disruption of the cell membrane. This hypothesis was substantiated by the data from flow cytometry using DiOC2as an indicator. The result showed that the red/green ratio which indicated bacterial membrane integrity was significantly decreased, similar to the known protonophore carbonyl cyanide 3-chlorophenylhydrazone. It is concluded that lupinifolin inhibits the growth of S. aureus by damaging the bacterial cytoplasmic membrane.
authors.affiliation: School of Preclinical Sciences, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.
authors.forename: Kamol
authors.initials: K
authors.lastname: Yusook
authors.affiliation: School of Preclinical Sciences, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.
authors.forename: Oratai
authors.initials: O
authors.lastname: Weeranantanapan
authors.affiliation: The Center for Scientific and Technological Equipment, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.
authors.forename: Yanling
authors.initials: Y
authors.lastname: Hua
authors.affiliation: Division of Health Promotion, Faculty of Health Science, Srinakharinwirot University, Ongkharak, Nakhon-Nayok, 26120, Thailand.
authors.forename: Pakarang
authors.initials: P
authors.lastname: Kumkrai
authors.affiliation: School of Preclinical Sciences, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand. nuannoi@sut.ac.th.
authors.forename: Nuannoi
authors.initials: N
authors.lastname: Chudapongse
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002462:Cell Membrane; D029866:Derris / Q000737:chemistry*; D005419:Flavonoids / Q000008:administration & dosage / Q000627:therapeutic use*; D018547:Plant Stems / Q000737:chemistry*; D013211:Staphylococcus aureus / Q000472:pathogenicity*
chemical_list: D000900:Anti-Bacterial Agents; D005419:Flavonoids; C448459:lupinifolin
keywords: Antimicrobial; Cell membrane disruption; Derris reticulata; Lupinifolin; Staphylococcus aureus