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

Background: 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. Objectives: The aim of this research was to investigate the chemical composition, antimicrobial, and antibiofilm properties of Malva sylvestris on some pathogenic bacteria. Methods: 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. Results: 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. Conclusions: 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.