Determination of In Vitro Antimicrobial Activity of Five Sri Lankan Medicinal Plants against Selected Human Pathogenic Bacteria

Abstract

Introduction. Antibiotic resistance is one of the greatest threats of the 21st century. Scientists search for potential antimicrobial sources that can cope with antibiotic resistance. Plants used in traditional medicine can be identified as potential candidates for the synthesis of novel drug compounds to act against antibiotic-resistant bacteria. Objective. To determine the potential antimicrobial effects of ethanol, aqueous, and hexane extracts of five Sri Lankan medicinal plants against four human pathogens. Methods. Asparagus falcatus (tubers), Asteracantha longifolia (whole plant), Vetiveria zizanioides (roots), Epaltes divaricata (whole plant), and Coriandrum sativum (seeds) were used in the study. Plant extracts were screened against four clinically important Gram-positive and Gram-negative bacterial strains, Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), and Klebsiella pneumoniae (ATCC 700603). Antibacterial activity of plant extracts were monitored using the agar disc diffusion method. Eight concentrations of each positive plant extract were used to determine the minimum inhibitory concentration (MIC) by 5-fold dilution of plant extracts yielding a serial dilution of the original extract. Results. Ethanol, aqueous, and hexane extracts of E. divaricata gave the maximum zones of inhibition of 16.3 mm, 7.4 mm, and 13.7 mm and MIC values of 0.48 mg/ml, 1.2 mg/ml, and 1.6 mg/ml, respectively, against S. aureus. Ethanol and hexane extracts of V. zizanioides gave the maximum zones of inhibition of 12.1 mm and 11.4 mm and MIC values 2.4 mg/ml and 0.003 mg/ml, respectively, against S. aureus. None of the other plants were effective against any microorganism used for the study. Conclusions. It can be concluded that E. divaricata and V. zizanioides crude ethanol, aqueous, and hexane extracts exhibited significant in vitro antibacterial activity against S. aureus, and the active compounds isolated from them can be potential sources for the synthesis of antibacterial drugs.

Comparison of In Vitro Antibacterial Activity of Epaltes divaricata and Vetiveria zizanioides against Methicillin-Resistant Staphylococcus aureus

“…Low polar active compounds present in the hexane extract may be responsible for this antimicrobial activity. As observed in our previous studies, compared to the MRSA strains, S. aureus ATCC standard (ATCC 25923) also showed similar susceptibility pattern for both plants [12]. is could be due to the genetic similarities between MSSA (ATCC 25923) and MRSA.…”

“…One of our previous studies also confirmed the presence of tannins, phenolic compounds, cardiac glycosides, flavonoids, alkaloids, and saponins in both E. divaricata and V. zizanioides plant extracts [12]. Dos Santos et al reported that β-vetivenene, khusimol, vetiselinenol, isovalencenol, vetivenic acid, α-vetivone, and β-vetivone are the major constituents of dichloromethane fraction of Vetiveria zizanioides [27].…”

“…One of our previous studies reported the antibacterial activity of E. divaricata and V. zizanioides against standard organisms such as Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), and Klebsiella pneumoniae (ATCC 700603) [ 12 ]. However, in vitro studies on these plants for multidrug-resistant organisms are not available.…”

In Vitro antioxidant and antibacterial activity of leaf extracts of Measa lanceolata

“…Disc diffusion assay: Antibacterial properties of the extracts were measured using the discdiffusion method. [20] Inoculums (100 μL) were spread evenly onto 20 mL Mueller-Hinton agar set in 90 mm Petri dishes using a sterile cotton swab. Sterilized paper disc (6 mm diameter) was impregnated with extract (20 μL) using a micropipette and firmly placed onto the inoculated agar ensuring even distribution to avoid overlapping of zones.…”

Chemical profiling, in vitro antimicrobial and antioxidant activities of pomegranate, orange and banana peel-extracts against pathogenic microorganisms

“…In light of the evidence of the rapid prevalence of multi-drug-resistant isolates, the need to discover new antimicrobial agents is of excessive importance. Many plants have been used because of their antimicrobial activities against pathogenic microorganisms, which are due to phytochemicals synthesized in the secondary metabolism of the plant such as flavonoids, saponins, tannins, phenolic compounds, alkaloids, anthraquinones, glycosides, and reducing sugars [8][9][10][11].…”