Bioassay-Guided Isolation of Antimicrobial Components and LC/QToF Profile of Plumeria obtusa : Potential for the Treatment of Antimicrobial Resistance.

The methanolic fraction (M-F) of the total extract (TE) of L. aerial parts showed promising antibacterial effects against the MDR (multidrug-resistant) gram-negative pathogens and O157:H7 [Shiga toxin-producing (STEC)]. In addition, M-F had a synergistic effect (in combination with vancomycin) against the MDR gram-positive strains MRSA (methicillin-resistant ) and . After treating the - and STEC-infected mice with M-F (25 mg/kg, i.p.), the level of IgM and TNF-α was decreased and the severity of pathological lesions were reduced better than that observed after administration of gentamycin (33 mg/kg, i.p.). Thirty-seven compounds including 10 plumeria-type iridoids and 18 phenolics, 7 quinoline derivatives, 1 amino acid, and 1 fatty acid were identified in TE using LC/ESI-QToF. Furthermore, five compounds; kaempferol 3--rutinoside (), quercetin 3--rutinoside (), glochiflavanoside B (), plumieride (), and 13--caffeoylplumieride () were isolated from M-F. was active against (MIC of 64 μg/mL) and STEC (MIC of 32 μg/mL). These findings suggested that M-F and are promising antimicrobial natural products for combating MDR and STEC nosocomial infections.