Preparation of Stable Branched DNA Nanostructures: Process of Cooperative Self-Assembly.

The construction of functionalizable branched DNA (bDNA) relies on the designing of oligonucleotides and exploitation of their complementary chemistries. The stability of these structures largely depends on the hybridization specificity of the contributing oligonucleotides. However, most of the bDNA structures are not found suitable for in vivo application due to poor yield owing to uncharacterized hybridization efficiency and instability in biological fluids. In this report, our group has explored a mechanistic way for studying the hybridization pathway of genomic sequence derived oligonucleotides that are self-assembled to fabricate robust bDNA structures. The effect of change in nucleotide sequences on bDNA stability was studied by taking oligonucleotides derived from primers of different genes. Additionally, the stability of the bDNA in solutions with different pH, salts, and DNaseI which mimics physiological environment was reported. It was found that genomic sequence derived oligonucleotides self-assembled in a cooperative manner to yield the designed bDNAs, which are stable in physiological environment.

Antioxidant activity, antibacterial potential and characterization of active fraction of Dioscorea pentaphylla L. tuber extract collected from Similipal Biosphere Reserve, Odisha, India

ABSTRACT Dioscorea pentaphylla L., a wild tuber is used both as food and medicines among different ethnic groups of Similipal Biosphere Reserve, India. Tubers are used against skin infections. In order to establish and confirm tribal claims, methanol extract was subjected to fractionation. The active fraction (DP1) was subsequently used for further purification and NMR (Nuclear magnetic resonance) characterization. The phytochemical analysis revealed the presence of saponin groups. The antibacterial activity of DP1 was done against selected bacterial strains (Salmonella typhi, Shigella flexneri, Streptococcus pyogenes, Streptococcus mutans and Vibrio cholerae) using DD (disc diffusion), AWD (agar well diffusion) and broth dilution assay. The activity was compared with antibiotics Penicillin and Kanamycin. It was observed that DP1 showed significant inhibitory activity against the tested bacteria. The characterization of DP1 through NMR analysis and presence of proton in carbon position at C-3, C-19, C-18, C-21 and C-27 was same as the known compound "Diosgenin". Therefore, isolated compound was confirmed to be Diosgenin. The study for the first time showed that, diosgenin present in D. pentaphylla tuber was responsible for antibacterial and antioxidant potential. Present study highlights the importance of Dioscorea species as sources of diverse secondary metabolites for the isolation of active compound(s).

In Vitro Antibacterial and Antioxidant Studies of Croton roxburghii L., from Similipal Biosphere Reserve.

In vitro antibacterial activities of acetone, ethanol, methanol and water extracts of leaves and bark of Croton roxburghii L. studied against ten human pathogenic bacterial strains showed significantly higher activity in acetone extract and least activity in case of aqueous. Minimal inhibitory concentration (MIC) values of all extracts ranged between 0.62 and 10 mg/ml, while minimal bactericidal concentration (MBC) values ranged from 1.25 to values greater than 10 mg/ml. The antioxidant assays viz. DPPH, hydrogen peroxide scavenging, iron reducing and iron chelating assays along with total phenol and ascorbic acid content were carried out with aqueous extracts of leaves and bark. While the total phenol contents in leaves and bark extracts were 0.766 ± 0.014 and 0.735 ± 0.028% respectively their ascorbic acid contents were found to be 0.252 ± 0.019 and 0.431 ± 0.013% respectively. DPPH activities in both (leaves and bark) extracts increased with the increase in concentrations. Iron chelating capacity of leaves extract is significantly higher than that of the bark. Leaves extract showed an increase in percentage of scavenging property with the increase in concentrations. Plant extracts showed low amount of iron reducing property at all concentrations. Hydrogen peroxide scavenging properties of bark was low than that of the leaves.