Phytochemical Composition, Antibacterial, and Antibiofilm Activity of Malva sylvestris Against Human Pathogenic Bacteria

Considering the increased rate of microbial resistance to antibiotics and chemical side effects of antibiotics, there is a need for an alternative antimicrobial agent with fewer complications. Medicinal plants are rich resources of phytochemical compounds with antibacterial activity that could fight off this problem.

The aim of this research was to investigate the chemical composition, antimicrobial, and antibiofilm properties of Malva sylvestris on some pathogenic bacteria.

Antibacterial effect of the extract was assessed by the well diffusion and broth microdilution methods against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli. The anti-biofilm property of the extract was also examined using the crystal violet assay. Finally, the chemical constituents and phenolic compounds of the extract were determined by gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC), respectively.

The methanolic extract of M. sylvestris showed antimicrobial activity against all tested Gram-negative and Gram-positive strains by the agar well diffusion method. The minimum inhibitory concentration (MIC) of the extract ranged from 21.9 ± 0.1 to 51.9 ± 0.5 mg/mL against the tested microorganisms. In addition, the minimum bactericidal concentration (MBC) spanned from 43.7 ± 0.1 to 85.8 ± 0.3 mg/mL. The biofilm inhibitory concentration (BIC50) of the extract was found to be 40 - 87 mg/mL against the tested bacteria. Analysis of the extract by GC-MS indicated that the most abundant compounds were 1-heptacosanol (38.41%), 17-Pentatriacontene (19.78%), and 6,9,12,15-docosatetraenoic acid, methyl ester (8.08%). High-performance liquid chromatography confirmed the presence of apigenin (6.84 ppm) and salicylic acid (1.5 ppm) as phenolic compounds in M. sylvestris methanolic extract.

The results of this study represent the high potency of M. sylvestris extract as a source of biologically-active compounds for the development of future phytotherapeutic products with antibacterial and antibiofilm activity.