Mechanistic study of 3-Methoxy-5-hydroxy-2-(3-methyl-2-butenyl) bibenzyl from pigeon pea against MRSA and biofilms: a highly promising natural inhibitor.

AIMS: The study aimed to investigate the anti-methicillin-resistant Staphylococcus aureus (MRSA) and anti-biofilm activity of 3-methoxy-5-hydroxy-2-(3-methyl-2-butenyl) bibenzyl (DELC) isolated from Cajanus cajan (L.) Millsp (pigeon pea) leaves, while evaluating its biocompatibility and exploring its potential as an antibiotic alternative.

METHODS AND

RESULTS

DELC exhibited potent anti-MRSA activity, with a minimum inhibitory concentration (MIC) of 3.12 μg/mL and MBC of 6.25 μg/mL. At 2 × MIC, it achieved complete eradication of 106 CFU/mL MRSA within 120 min, demonstrating faster bactericidal action than vancomycin.

ANTIBIOFILM STUDIES: 2 × MIC DELC inhibited biofilm formation as effectively as 4 × MIC vancomycin. In mature biofilms, merely 1/2 × MIC DELC penetrated and eliminated a portion of embedded viable bacteria-a feat unattainable even with 8 × MIC vancomycin.

MECHANISTIC STUDIES: DELC induced oxidative stress, generating ROS that damaged the bacterial membrane, causing nucleic acid leakage. It also suppressed α-hemolysin secretion.

RNA-SEQ ANALYSIS REVEALED: At 1 × MIC, DELC blocked ATP synthesis and repair systems, leading to metabolic inhibition and virulence attenuation. At ≥2 × MIC, it directly lysed bacterial cells.

BIOCOMPATIBILITY: DELC showed no hemolysis or cytotoxicity, indicating excellent safety.

CONCLUSIONS

DELC demonstrates potent anti-MRSA activity characterized by rapid bactericidal effects, a concentration-dependent dual mechanism-metabolic inhibition at low concentrations progressing to direct cellular lysis at higher concentrations, and superior antibiofilm capacity. Its outstanding biocompatibility strongly supports its clinical translation potential.