Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant clinical challenge due to its multidrug resistance, particularly to β-lactam antibiotics. This study comprehensively evaluated the natural compound emodin for its anti-MRSA activity, mechanisms of action, and potential for synergy with β-lactam antibiotics. Our findings demonstrate that emodin dose-dependently inhibits MRSA growth and abrogates biofilm formation at 2× MIC. Mechanistic studies revealed that emodin compromises cell membrane and wall integrity, induces oxidative stress, and downregulates the virulence factors SPA and EsxA. Furthermore, emodin acted synergistically with β-lactam antibiotics: it enhanced the ability of cefalexin to block bacterial adhesion and invasion of HaCat cells, and potentiated the efficacy of amoxicillin in clearing MRSA from infected macrophages. In conclusion, emodin employs a multi-target mechanism against MRSA and can resensitize the bacterium to conventional β-lactam antibiotics, presenting a promising strategy for combination therapy that may help curb antibiotic use and resistance development.

Three transition metal coordination complexes, {[Co(2,4-DCP)₂(μ ₂-H₂O)(H₂O)₂] · (H₂O)₂} _n (1), [Zn(2,4-DCP)(IN)] _n (2), and [Mn₂(2,4-DCP)₃(DMPY)₂(μ ₂-H₂O)(H₂O)] · (2,4-DCP) · 0.2(H₂O) (3) (2,4-DCP = 2,4-dichlorophenoxyacetate, IN = isonicotinate, DMPY = 5,5′-dimethyl-2,2′-bipyridine), have been prepared under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Complex 1 displays a 1-D chain through cobalt and bridging water molecules with Co ··· Co distance of 4.028(2) Å. Complex 2 shows a 2-D (4,4) net, which is extended into a 3-D supramolecular framework by weak hydrogen-bonding interactions. Complex 3 consists of discrete dinuclear cations, 2,4-DCP counter ions and free water molecules, which are assembled into a packing structure through π ··· π stacking of inversion-related DMPY ligands and hydrogen bonds. Magnetic susceptibility measurements show weak antiferromagnetic interactions in 1. The photoluminescence and lifetime of 2 in the solid state have also been studied.

Two new isostructural 1-D lanthanide coordination polymers, {[Ln(2,4-dcp)₃(phen)] _n [(Ln = Eu (1); Tb (2)], [2,4-dcp = 2,4-dichlorophenoxyacetate, phen = 1,10-phenanthroline], were obtained under hydrothermal conditions and characterized by IR spectroscopy, elemental analyses, thermogravimetry analyses, powder X-ray diffraction, and single-crystal X-ray diffraction. Both structures exhibit similar 1-D infinite chains with a {Ln₂(2,4-dcp)₆(phen)₂} dimeric repeat unit, with lanthanides in an eight-coordinate environment. The results of thermal analysis indicate that 1 and 2 are quite stable to heat. 3-D fluorescence spectra of 1 and 2 were detected at room temperature under excitation and the emission wavelengths of 250–460 nm and 420–750 nm with the same interval of 5 nm, respectively. Interestingly, 1 and 2 possess longer fluorescence lifetimes than other complexes (τ = 1.61 ms for 1 at 611 nm; 1.79 ms for 2 at 543 nm).

Two new isostructural dinuclear complexes, Ln₂(4-cpa)₆(phen)₂ (Ln = Eu (1); Tb (2), 4-cpa^– = 4-chlorophenylacetate, phen = 1,10-phenanthroline), have been hydrothermally synthesized and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The lanthanides are bridged by two bidentate and two tridentate carboxylato groups to give centrosymmetric dimers with Ln···Ln separations of 3.967(2) and 3.937(3) Å for 1 and 2, respectively. Each metal is nine-coordinate and exhibits a distorted tricapped trigonal prismatic geometry. Both 1 and 2 emit characteristic, intense luminescence at room temperature with lifetimes up to 0.890 ms (at 611 nm) and 0.995 ms (at 543 nm). Poor luminescence efficiency is observed for 2. 4-Chlorophenylacetate, 1 and 2 have been screened for their phytogrowth-inhibitory activities against Brassica napus L. and Echinochloa crusgalli L., and the results are compared with the activity of quizalofop-P-ethyl.