Rapid screening for minimum inhibitory concentration of medicinal plant extracts against human pathogenic bacteria

Abstract

In the present study, crude extracts of different parts of six medicinal plant species have been screened for antibacterial activity through resazurin dye reduction assay. The crude extracts of Coleus strobilifer, Phyllanthus reticulatus, Acalypha paniculata, Solanum erianthum, Curculigo orchioides, and Spatholobus parviflorus were prepared with the solvents, petroleum ether, methanol and ethanol by Soxhlet extraction method. Resazurin titreplate assay was done for screening the plant extracts for minimum inhibitory concentration (MIC) the pathogenic bacteria, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae. The results revealed that the crude extracts of various parts of the plants obtained using three different solvents were capable of inhibiting the test bacteria with the MIC values ranging from 125 μL to >1000 μL. The stem extracts of C. strobilifer and A. paniculata showed the least antibacterial activity with the MIC values >1000 µL. The leaf extracts of S. erianthum showed a MIC value of 250-500 µL against S. aureus, P. aeruginosa and K. pneumoniae. The results revealed that the rhizome extract of C. orchioides and fruit extracts of S. parviflorus have good antibacterial activity and can be tested further with specific trials to develop antibacterial drugs. For initial screening of medicinal plants for antibacterial activity is faster, more accurate and reliable with resazurin dye reduction method.