Oxidative stress is initiated by free radicals, which seek stability through electron pairing with biological macromolecules in healthy human cells and cause protein and DNA damage along with lipid peroxidation. Many phytochemicals have been found to play as potential antioxidants and antimicrobials. In the present study antioxidant and antistaphylococcal activities of Bauhinia variegata, Tinospora cardifolia and Piper longum have been determined. Total phenolic contents in plant extracts were estimated and different amounts of phenolic contents were found in B. variegata, T. cardifolia and P. longum extracts. The antioxidant activity of the extracts was compared with standard antioxidants such as, BHA, BHT, quercetin, ascorbic acid and propyl gallate. The % scavenging activity gradually increased with increasing concentrations of the test extracts in DPPH radical scavenging assay. Dose dependent antioxidant activity pattern was also observed in phosphomolybdate assay. Antioxidant activity was directly correlated with the amount of total phenolic contents in the extracts. As compared to B. variegata, the extracts from other two plants exhibited higher antioxidant activity. In disc diffusion assays several solvent extracts derived from test plants inhibited the growth of Staphylococcus aureus. Maximum inhibitory efficacy was observed in T. cardifolia extracts. However, the lowest minimum bactericidal concentration (MBC) (0.43 mg/ml) was recorded for ethyl acetate and acetone extracts of P. longum. This study demonstrates notable antioxidant and anti-staphylococcal roles assigned to some plant extracts tested.

Bacteriostatic efficacy of 16 crude extracts derived from different parts of Argemone mexicana Linn. (Papaveraceae) has been analyzed on entropathogenic bacteria such as Klebsiella oxytoca, Vibrio damsella, Enterobacter aerogenes and Escherichia coli. The bacteriostatic efficacy was elucidated using single disc diffusion method. The minimum inhibitory concentration (MIC) of the extracts showing higher efficacy against the test organisms was determined. The MICs of acetone extract of seed and aqueous extract of leaf on different bacteria tested were found to be between 0.005-0.02 mg/disc.

Isatin (1) underwent facile regioselective N-alkylation with various 2-chloro-3-chloromethylquinolines (2a-e) in the presence of KOt Bu in THF at 70°C to afford corresponding N-alkylated derivatives (3a-e). Chemical structures of products were characterized using FTIR, 1H, 13C NMR and Mass spectral studies. All the title compounds were screened for antimicrobial studies. Most of the tested compounds exhibited potent in vitro antimicrobial activity dose dependently.

Present review describes research on novel natural cyclobutane-containing alkaloids isolated from terrestrial and marine species. More than 60 biological active compounds have been confirmed to have antimicrobial, antibacterial, antitumor, and other activities. The structures, synthesis, origins, and biological activities of a selection of cyclobutanecontaining alkaloids are reviewed. With the computer program PASS some additional biological activities are also predicted, which point toward new possible applications of these compounds. This review emphasizes the role of cyclobutane-containing alkaloids as an important source of leads for drug discovery.
The Open Medicinal Chemistry Journal, 2008, 2, 26-37.