Structural properties and antioxidant activities of soybean protein hydrolysates produced by Lactobacillus delbrueckii subsp. bulgaricus cell envelope proteinase.

In this work, we investigated the structural and biological properties of soybean protein isolate (SPI) after 0-8 h hydrolyzation with cell envelope proteinase (CEP) extracted from Lactobacillus delbrueckii subsp. bulgaricus. CEP hydrolysis increased the ß-sheet and red-shifted the fluorescence peak, while decreasing the α-helix, indicating the unfolding of soybean proteins. Increased surface hydrophobicity and fluorescence of the soybean protein hydrolysates were correlated with the increased hydrophobic amino acid (from 209.67 to 217.6 mg/100 g). CEP tended to hydrolyze the N- and C-terminal regions of sequences dominated by Gly and Leu, which enhanced the antioxidant activity of the SPHs (lowest IC50s value of ABTS•+ and hydroxyl radical scavenging activity were 0.324 ± 0.006 mg/mL and 0.365 ± 0.001 mg/mL after 4 h hydrolysis). Comparison with the database of bioactive peptides suggested various potential biological activities, including antioxidant activity, angiotensin-converting enzyme inhibitory activity and dipeptidyl peptidase-IV inhibitory activity. The study findings have theoretical significance for the development of CEP hydrolysis and novel bioactive soybean peptides.

Novel 5-methyl-2-phenylphenanthridium derivatives as FtsZ-targeting antibacterial agents from structural simplification of natural product sanguinarine.

A novel series of 5-methyl-2-phenylphenanthridium derivatives were displayed outstanding activity against a panel of antibiotic-sensitive and -resistant bacteria strains compared with their precursor sanguinarine, ciprofloxacin and oxacillin sodium. Compounds 7 l, 7m and 7n were found to display the most effective activity against five sensitive strains (0.06-2 µg/mL) and three resistant strains (0.25-4 µg/mL). The kinetic profiles indicated that compound 7l possessed the strongest bactericidal effect on S. aureus ATCC25923, with the MBC value of 16 µg/mL. The cell morphology and the FtsZ polymerization assays indicated that these compounds inhibited the bacterial proliferation by interfering the function of bacterial FtsZ. The SARs showed that all the 4-methyl-substituted 5-methyl-2-phenylphenanthridium subseries could be further investigated as the FtsZ-targeting antibacterial agents.