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.

Plants produce wide variety of phytochemical compounds which have been known to perform most biological activities such as antimicrobial, anticancer, antioxidant activities etc. Plants which possess these medicinal properties are known to be medicinal plants. In this study, Annona muricata, Piper betle and Mentha spicata were collected from Chennai, Tamil Nadu, India. The crude extracts were taken using various solvents like acetone, ethanol, chloroform, toluene and petroleum ether. All the extracts were subjected for qualitative analysis for the phytochemicals. All the samples were also subjected for antibacterial activity and TLC bioautography analysis for antioxidants. Since they found to possess antioxidant activity, quantitative assay for antioxidant activity like DPPH and FRAP assays were performed.Keywords: Annona muricata, Piper betle and Mentha spicata