ABSTRACT

Medicinal plants represent potential sources of novel compounds with antibacterial and antibiofilm properties which could be used to combat the increasing problem of antimicrobial resistance in bacterial pathogens. In this study, the antibacterial and antibiofilm properties of methanol extracts of five medicinal plants used in traditional medicine were investigated against biofilm forming strains of Pseudomonas aeruginosa. Fresh leaves of Alchornea cordifolia, Dennetia tripetalia, Costus afer, Pterocarpus santalinoides and Moringa oleifera, collected from farm lands and bushes within Abia State were dried under shade for two weeks and pulverized using a mechanical grinder. The pulverized leaves were filtered using a fine mesh sieve to obtain a fine powder of the leaves of the different medicinal plants. The leaf powders were separately extracted with methanol. The inhibitory activity of the extracts against the growth of the test organisms was assessed using the agar well diffusion technique and the Minimum Inhibitory Concentration (MIC) was determined using well microdilution method. The antibiofilm properties were investigated using the crystal violet assay. The phytochemical analysis of the extracts and powders of the leaves was done using Column and Thin Layer Chromatography methods. Fractions from bioactivity guided fractionation were further analyzed by Gas Chromatography - Mass Spectrometry (GC-MS). The extracts of A. cordifolia, D. tripetalia and C. afer produced diameter of zone of inhibition ranging from 7.5 mm to 21 mm at a concentration of 10mg of extract per well, against the strains of P aeruginosa used in the study. The MIC values ranged from 0.31 mg/ml to I .25mg/ml. Alchornea cordifolia extract exhibited the highest inhibitory activity against all the test strains. The extracts of all the plants produced biofilm inhibition ranging from 57.3% to 67.2% against PAOI-L-PqSA Lux strain, the most active biofilm forming strain at the concentration of 2.5 mg. The percentage composition of phytochemical content of the leaves of A. cordifolia plant was alkaloids 1.85%, flavonoids 1.08%, terpenoids 1.05%, saponins 4.13%, and tannins 0.70%. The GC-MS analysis of A. cordifolia, revealed twenty compounds of which Dihydromorphine and Rhodopin with retention time (RT) of 16.53 minutes and 15.30 minutes, respectively, appeared to be the main compounds. The findings of this study have shown that the extracts of the medicinal plants, particularly, the extract of A. cordifolia, showed high antibacterial and antibiofilm properties and therefore represents a potential source of antibacterial and anti-biofilm compounds in the search for novel agents against resistant bacterial pathogens. Further research on the potential of A. cordifolia as a source of antibacterial and anti-biofilm agents is recommended.