Structure-function characterization and optimization of a plant-derived antibacterial peptide.
Crushed seeds of the Moringa oleifera tree have been used traditionally as natural flocculants to clarify drinking water. We previously showed that one of the seed peptides mediates both the sedimentation of suspended particles such as bacterial cells and a direct bactericidal activity, raising the possibility that the two activities might be related. In this study, the conformational modeling of the peptide was coupled to a functional analysis of synthetic derivatives. This indicated that partly overlapping structural determinants mediate the sedimentation and antibacterial activities. Sedimentation requires a positively charged, glutamine-rich portion of the peptide that aggregates bacterial cells. The bactericidal activity was localized to a sequence prone to form a helix-loop-helix structural motif. Amino acid substitution showed that the bactericidal activity requires hydrophobic proline residues within the protruding loop. Vital dye staining indicated that treatment with peptides containing this motif results in bacterial membrane damage. Assembly of multiple copies of this structural motif into a branched peptide enhanced antibacterial activity, since low concentrations effectively kill bacteria such as Pseudomonas aeruginosa and Streptococcus pyogenes without displaying a toxic effect on human red blood cells. This study thus identifies a synthetic peptide with potent antibacterial activity against specific human pathogens. It also suggests partly distinct molecular mechanisms for each activity. Sedimentation may result from coupled flocculation and coagulation effects, while the bactericidal activity would require bacterial membrane destabilization by a hydrophobic loop. (+info)
Seed germination, seedling traits, and seed bank of the tree Moringa peregrina (Moringaceae) in a hyper-arid environment.
In vivo and in vitro hypotensive effect of aqueous extract of Moringa stenopetala.
BACKGROUND: Moringa stenopetala, Baker f. (Moringaceae) is used for food and medicine in Southern Ethiopia. OBJECTIVE: To substantiate the hypotensive effect of M. stenopetala in vivo and in vitro. METHODS: An in vivo experiment was carried out on male guinea pigs anaesthetized with pentobarbital. The arterial blood pressure was recorded from a carotid artery filled with heparinized saline via an arterial cannula connected to a pressure transducer. For the in vitro experiment the descending thoracic aorta was removed and kept moistened in Krebs-Henseleit solution and then mounted in a 20ml tissue bath maintained at 37 degrees C and bubbled with a mixture of 95% oxygen and 5% carbon dioxide. RESULTS: Crude aqueous leaf extract of M. stenopetala caused significant fall in systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial blood pressure (MABP) at doses of 10, 20, 30 and 40 mg/kg in normotensive anaesthetized guinea pigs (n = 12). The effect might have been mediated by non-autonomic nervous system as the effect is not altered by atropine and propranolol. The extract also caused significant dose and time dependent inhibition of K(+) induced contraction on guinea pig aorta. CONCLUSION: M.stenopetala has blood pressure lowering effect substantiating the use of the plant in traditional medicine. (+info)
Effects of methanolic extract of Moringa oleifera leaves on semen and biochemical parameters in cryptorchid rats.
While anti-oxidant effects of Moringa oleifera in much oxidative stress related diseases have been well reported, cryptorchidism on the other hand has been shown to cause oxidative stress. However, study is scanty on the likely role of Moringa oleifera in reducing cryptorchidism-induced oxidative stress in rats has not been studied. The present study looked into the effects of methanolic extract of Moringa oleifera leaves (MEMO) on semen and biochemical parameters in cryptorchid rats. Twenty male albino rats (200-250 g) were randomly divided into 4 groups (n=5 each). Groups A and B were sham-operated and treated with corn-oil and 200 mg/kg of MEMO respectively, while groups C and D were rendered cryptorchid and also treated with corn-oil and 200 mg/kg of MEMO respectively. Cryptorchid rats had lower testicular weight, sperm count, germ cell count, testicular superoxide dismutase (SOD) concentration, testicular total protein and higher testicular malondialdehyde (MDA) concentration compared to sham-operated rats. MEMO had no significant effect on testicular weight and MDA concentration, while it significantly increased sperm count, germ cell count, testicular SOD and total protein in the cryptorchid rats. The present study suggests that MEMO ameliorates cryptorchidism associated germ cell loss and oxidative stress. (+info)