Screening of certain medicinal plants from India for their anti-quorum sensing activity.

Discovery of quorum sensing (QS) system to coordinate virulence and biofilm formation in bacterial pathogens has triggered search for safe, stable and non-toxic anti-QS compounds from natural products. Ethanolic extracts of 24 Indian medicinal plants were tested by agar well and disc diffusion assay for anti-QS activity using Chromobacterium violaceum (CV12472 and CVO26) reporter strains. AHL from C. violaceum CV31532 was isolated and partially purified for its use in CVO26 based bioassay. Effect on swarming-motility of Pseudomonas aeruginosa (PAO1) was also recorded at sub-MIC concentrations of extracts. Of the 24 medicinal plants screened Hemidesmus indicus (L.) Schult (root), Holarrhena antidysenterica (Roth)A.DC. (bark), Mangifera indica L. (seed) Punica granatum L. (pericarp) and Psoralea corylifolia L. (seed) demonstrated varying level of inhibition of violacein production in the reporter strains. Moreover, a significant reduction in swarms was recorded over control. The inhibition of violacein production and swarming motility may be due to direct or indirect interference on QS by active constituents or the interactive effect of different phytocompounds present in the extracts. These plant extracts may be selected for activity guided fractionation to identify and characterize the active principle

Antimutagenic activity of methanolic extracts of four ayurvedic medicinal plants.

Methanolic extracts of Acorus calamus (Rhizome), Hemidesmus indicus (Stem), Holarrhena antidysenterica (Bark) and Plumbago zeylanica (Root), were tested for their antimutagenic potential. These extracts, at tested concentrations, showed no sign of mutagenicity to Salmonella typhimurium tester strains. The extracts of the plants exhibited varying level of antimutagenicity. At a dose of 100 microg/plate, the extracts exhibited the inhibition of His+ revertants from 18.51% to 82.66% against direct acting mutagens, methyl methanesulphonate (MMS) and sodium azide (NaN3) induced mutagenicity in Salmonella tester strains TA 97a, TA 100, TA 102 and TA 104. However, at lower concentrations (25 and 50 mcirog/plate) of the plant extracts, a decrease in antimutagenic activity was recorded. Dose dependent antimutagenic activity of the extracts is also evident from linear regression analysis of the data. The over all antimutagenic potential of above four extracts was found to be in order of A. calamus > H. indicus > H. antidysenterica > P. zeylanica. Further, total phenolic content of these extracts did not correlate with its antimutagenic activity in A. calamus and P. zeylanica.