Cinnamomum verum Bark Methanolic Extract: Antibacterial, Antibiofilm Activity and Preliminary Anti

Phytochemical characterization of the Cinnamomum verum methanolic bark extract

The methanolic bark extract of Cinnamomum verum was chemically profiled by HPLC‑MS, which identified 17 constituent compounds. The most abundant quantified component was trans‑cinnamaldehyde, with other notable constituents including quinic acid, rutin, and protocatechuic acid. The chemical profiling provided the basis for connecting observed biological activity with specific phytochemicals and for selecting ligands for in silico docking against bacterial targets.

In vitro antibacterial activity: MIC, MBC and bactericidal assessment

Antibacterial potency of the extract was assessed against reference strains and multidrug‑resistant clinical isolates using broth microdilution to determine minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). Reported MIC values ranged from 0.625 to 5 mg/mL, and MBC values ranged from 2.5 to 20 mg/mL. The MBC/MIC ratios reported were consistent with bactericidal activity for the tested organisms. Among isolates tested, imipenem‑resistant Acinetobacter baumannii strains exhibited the highest susceptibility to the extract.

Antibiofilm activity and concentration dependence

Biofilm biomass was evaluated with the crystal‑violet assay. The extract reduced biofilm biomass in a manner that depended on both concentration and bacterial strain, demonstrating antibiofilm effects that paralleled the antimicrobial findings. The study reports concentration‑ and strain‑dependent reductions in biofilm but does not provide mechanistic confirmation of how biofilm disruption occurs.

Preliminary antibiotic–extract interaction screening by disk diffusion

A disk‑diffusion screening was used to explore interactions between the extract and selected antibiotics. Outcomes were variable and depended on both the antibiotic and the bacterial isolate. Some combinations produced increased inhibition zone diameters—for example, cefoxitin and fosfomycin showed notable increases against MRSA, and selected combinations increased zones against A. baumannii isolates. Other combinations were unchanged or produced smaller zones. The authors emphasize that these disk‑diffusion observations are preliminary screening results and that formal pharmacological synergy (for example, checkerboard or time‑kill assays) was not established in this work.

Exploratory molecular docking and prioritized phytochemicals

Molecular docking was used as an exploratory, hypothesis‑generating tool to investigate potential interactions between identified phytochemicals and three bacterial targets: GyrB, LasA, and PBP1a. Docking results prioritized several compounds for subsequent target‑based validation, specifically quercetin, 1,3‑di‑O‑caffeoylquinic acid, and quercetin‑3‑O‑rhamnoside. The docking step is presented as a means to suggest candidates for follow‑up rather than as definitive evidence of target engagement or in vivo activity.

Methods summary and experimental approaches

Key experimental approaches reported in the study include:

• Phytochemical profiling by HPLC‑MS to identify and quantify extract constituents.
• Broth microdilution assays to determine MIC and MBC values against reference and multidrug‑resistant strains.
• Crystal‑violet staining to quantify biofilm biomass and assess antibiofilm activity.
• Disk‑diffusion screening to evaluate preliminary antibiotic–extract interactions across antibiotics and isolates.
• Molecular docking as a computational, hypothesis‑generating approach targeting GyrB, LasA, and PBP1a.

The authors framed molecular docking and disk‑diffusion interaction data as exploratory; further, quantitative and mechanistic assays were recommended for confirmation.

Key findings, interpretation, and limitations

Principal findings from the reported experiments are:

• The extract contains a chemically diverse set of phytochemicals with trans‑cinnamaldehyde as the major quantified compound.
• The extract inhibited all tested bacterial strains with MICs of 0.625–5 mg/mL and MBCs of 2.5–20 mg/mL, with MBC/MIC ratios indicative of bactericidal activity.
• Biofilm biomass was decreased in a concentration‑ and strain‑dependent fashion.
• Disk‑diffusion screening revealed antibiotic‑ and isolate‑dependent modulation of inhibition zones; some increases were observed (notably cefoxitin and fosfomycin versus MRSA and selected combinations vs A. baumannii), but pharmacological synergy was not demonstrated.
• Docking prioritized quercetin, 1,3‑di‑O‑caffeoylquinic acid, and quercetin‑3‑O‑rhamnoside for further validation.

Limitations explicitly implied by the study design include the preliminary nature of antibiotic‑interaction screening by disk diffusion (which does not quantify synergy), and the hypothesis‑generating role of molecular docking (which does not confirm biochemical target engagement or cellular mechanism). The source does not report in vivo efficacy, toxicity, or pharmacokinetic data.

Implications and directions for further validation

The results support further investigation of Cinnamomum verum bark extracts and selected phytochemicals as potential antibacterial and antibiofilm agents, particularly against multidrug‑resistant organisms such as imipenem‑resistant Acinetobacter baumannii and MRSA. Follow‑up studies recommended by implication include quantitative synergy testing (checkerboard, fractional inhibitory concentration indices, and time‑kill assays), biochemical or biophysical validation of docking hits against GyrB, LasA, and PBP1a, and assessment of safety and efficacy in relevant in vivo models. Until such validation is performed, the current findings should be interpreted as preliminary and hypothesis‑generating.