Evaluation of Antimicrobial Properties of African Basil (Ocimum gratissimum) and Tassel Flower (Emilia coccinea) Leaf Extracts

Abstract

The use of plant extracts and phytoconstituents with antimicrobial properties may provide therapeutic benefits and application in consumer products such lotions and soaps, and active food packaging. The objective of this study was to assess the efficacy of water, methanol, butanol and ethyl acetate extracts of Ocimum gratissimum leaf (OGL) in inhibiting the growth of selected bacteria (E. coli O157:H7 (ATCC 43894), Salmonella enterica serovar Typhimurium DT‐104 (CDC H3380), Aeromonas hydrophila K144, and Pseudomonas aeruginosa (ATCC 7700)). In a parallel study, water, methanol, and butanol extracts of Emilia coccinea leaf (ECL) and OGL were also tested against E. coli, Pseudomonas aeruginosa, and Staphylococcus aureus. To screen for antimicrobial activity, the susceptibility of these selected pathogens and non‐pathogenic bacteria was determined using the disk diffusion assay. Selected antibiotics such as tetracycline, streptomycin, ampicillin and kanamycin were used as positive control. Following incubation, zone of inhibition differed between control and extracts, with larger zone of inhibition in the OGL butanol extract than the water, methanol, and ethyl acetate extracts in all the four pathogens tested, and a smaller zone of inhibition for E. coli, Salmonella and Pseudomonas cultures. Aeromonas hydrophila K144 cultures were found to be susceptible to butanol extract showing 10 mm of clearance zone. Incubation of ampicillin with Aeromonas hydrophila K144, Salmonella enterica serovar Typhimurium DT‐104 (CDC H3380) and Pseudomonas aeruginosa (ATCC 7700) led to minor changes in the zone of inhibition of these antimicrobials. P. Aeruginosa and S. aureus were resistant and susceptible to all antibiotic controls tested, respectively. E. coli, P. aeruginosa, S. aureus were all susceptible to the methanol and butanol extracts of OGL and ECL. Butanol and methanol extracts of Ocimum gratissimum and Emilia coccinea leaf could be suitable alternative to some chemical antimicrobials, satisfying consumer demand for natural products.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.