The use of medicinal plants to treat infections as a practice can be witnessed since the prehistoric era. Even as on date three-quarter of the world's population totally depends on plants for their primary health care benefits. In this study, secondary metabolites like alkaloids, flavonoids, tannins and saponins were extracted from four medicinal plants viz. Cassia alata, Thespesia populnea, Euphorbia hirta and Wrightia tinctoria and characterized by UV, TLC, FTIR and GCMS analysis. The metabolites were checked for the antibacterial activity using agar well diffusion method and swarming motility assay against Pseudomonas aeruginosa. The alkaloids and saponins of Cassia alata, Euphorbia hirta, Thespesia populnea and Wrightia tinctorial showed dose-response antibacterial activity. The highest antibacterial activity of 1.9 cm was seen for the tannin of Wrightia tinctoria and saponin of Euphorbia hirtaat 16µg concentration. Flavonoid of Euphorbia hirta, Cassia alata and Wrightia tinctorial showed good percentage inhibition of free radicals in DPPH scavenging assay supportive of the antioxidant property. The highest percentage inhibition of 88.75% was noted for tannin of Euphorbia hirta at 50 µg concentration. Antioxidant activity was also checked qualitatively by TLC bioautography and quantitatively for its reducing power on the free radicals by FRAP and phosphomolybdenum assay. The extracted metabolites especially alkaloids were able to restrict the movement of micro organisms to a confined space which was evident from the swarming test.
The aqueous extracts of Euphorbia hirta was used to synthesise silver nanoparticles using bioreduction method. The nanoparticles were characterised by UV Vis spectroscopic analysis, SEM, EDX, AFM, XRD analysis. The silver nanoparticles were also tested for antibacterial activity in Pseudomonas aeruginosa and Bacillus subtilis. The minimum inhibitory concentration for the synthesised nano particles were also tested against the two bacterial species for the least concentration of 0.5µg/mL. The swarming motility assay and protein leakage assay was also tested for the nanoparticle. The silver nanoparticles were found to be much effective.
Silver nano particles synthesised from the leaves of Wrightia tinctoria were characterised by following instrumental analysis -UV Vis spectroscopy, Scanning Electron Microscopy, Energy dispersive X-ray spectroscopy, Atomic force microscopy and X-ray diffraction. The interaction of the silver nanoparticle to the microorganism was studied in Pseudomonas aeruginosa and Bacillus subtilis through agar diffusion method, minimum inhibitory concentration, swarming motility assay and protein leakage assay. The nanoparticles were found to be more effective against the bacteria used in this study.
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