Isolation of 1,4-naphthalenedione, an antibacterial principle from the leaves of Holoptelea integrifolia and its activity against β-lactam resistant Staphylococcus aureus.

Antimicrobials derived from plants have been receiving increasing attention in recent years. Antimicrobial activities of a number of phytochemicals have been reported. Many present day antibiotics are ineffective against several pathogenic organisms. About 90% of Staphylococcus aureus isolates from clinical specimens is reported to have resistance against β-lactam antibiotics. In the present study, the effect of hexane, diethyl ether, acetone and water extracts of leaves of a medicinal plant Holoptelea integrifolia has been tested against β-lactam resistant strain of S. aureus in presence of antibiotics such as ampicillin, amoxicillin, cefotaxime and ceftriaxone. The diethyl ether extract has shown the maximum antibacterial activity and the active principle is found to be 1,4-naphthalenedione which is characterized by GC-MS and FTIR spectroscopy. The minimum inhibitory concentration (MIC) of the compound is found to be 4 mg/ml. Structural similarity of this compound with a func- tional group of a β-lactamase-resistant antibiotic indicates that 1,4-naphthlenedione may be acting as an inhibitor to β-lactamase.

Conformation of an octapeptide fragment (2-9) of kaliocin-1 in DMSO-d6 by 1H NMR and restrained molecular dynamics.

Kaliocin-1, a 31-residue synthetic peptide (FFSASCVPGADKGQFPNLCRLCA GTGENKCA), which has shown the antimicrobial activity forms the 152-182 fragment of human lactoferrin (HLf). As the octapeptide FSASCVPG forms the 2-9 fragment of kaliocin-1, in the present study, its conformation in dimethyl sulfoxide-d6 (DMSO-d6) has been determined using two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy as well as restrained molecular dynamics. Sequence specific assignments of all the 1H resonances have been carried out using 2D correlation experiments (2D DQF-COSY, TOCSY and ROESY). In dimethyl sulfoxide-d6 at 25 degrees C, the octapeptide adopts a predominantly extended backbone conformation. The calculated structure resembles closely with the reported structure of the corresponding fragment of HLf. The peptide also has sequence and structural similarity with the corresponding fragments of lactoferrins from other organisms.

Antibacterial property of goat milk lactoperoxidase.

The goat milk lactoperoxidase was purified using CM sephadex C-50 and sephadex G 100. The purity of protein was confirmed by SDS-PAGE. The purified protein was found to have antibacterial action against most of the disease causing bacteria.