Characterization of antimicrobial compounds from a common fern, Pteris biaurita.

Methanol extract was prepared from the fronds of Pteris biaurita and partial purification was done by solvent partitioning with diethyl ether and ethyl acetate, followed by hydrolysis and further partitioning with ethyl acetate. The three fractions, thus obtained were bioassayed separately against five test fungi--Curvularia lunata, Fomes lamaoensis, Poria hypobrumea, Fuasrium oxysporum and a bacterium--Bacillus pumilus, by spore germination, radial growth and agar cup techniques. Results revealed that ethyl acetate fraction (III) contained the active principle. TLC plate bioassay of the active fraction revealed inhibition zone at an Rf of 0.5-0.65. Silica gel from this region was scraped, eluted in methanol and subjected to UV-spectrophotometric analysis. An absorption maxima of 278 nm was recorded. HPLC analysis of TLC-eluate revealed a single peak with retention time of 8.1 min. GC-MS analysis revealed six major peaks in the retention time range of 7.2-10.9 min. Comparison with GC-MS libraries revealed that the extracts may contain a mixture of eicosenes and heptadecanes.

Biochemical responses of Camellia sinensis (L.) O. Kuntze to heavy metal stress.

Three heavy metals-mercury (II), copper (II) and nickel (II), each at a concentration of 10 and 100 micrograms/ml, were tested for their effects on various biochemical constituents of tea leaves. Both NI (II) and Hg (II) decreased the phenolic contents, while Cu (II) increased it to some extent. The metal treatments enhanced the activity of phenyl alanine ammonia lyase (PAL), while the activity of poly phenol oxidase (PPO) showed a decline. Heavy metal stress also decreased the chlorophyll content of the leaves, along with a significant reduction in Hill activity. Proline content increased significantly in all treatments.