Cymbopogon citratus, commonly known as lemongrass, has been shown to have antioxidant, antimicrobial and chemo-protective properties. Citral, a monoterpenoid, is the major constituent of C. citratus that gives off a lemony scent and is postulated to be responsible for most of its actions. In addition, C. citratus has been traditionally used to treat gastrointestinal discomforts, however, the scientific evidence for this is still lacking. Thus, the aim of the present study was to investigate the effect of the extracts of various parts of C. citratus (leaves, stems and roots) and citral on the visceral smooth muscle activity of rabbit ileum. The effect of the test substances were tested on the spontaneous contraction, acetylcholine (ACh)-and KCl-induced contractions. Citral at doses between 0.061 mM to 15.6 mM and the extract of leaves at doses between 0.001 mg/mL to 1 mg/mL significantly reduced the spontaneous, ACh-and KCl-induced ileal contractions. When the ileum was incubated in K + -rich-Ca 2+ -free Tyrode's solution, it showed only minute contractions. However, the strength of contraction was increased with the addition of increasing concentrations of CaCl2. The presence of citral almost abolished the effect of adding CaCl2, while the leaf extract shifted the calcium concentration-response curve to the right, suggesting a calcium antagonistic effect. These results were similar to that elicited by verapamil, a known calcium channel blocker. In addition, the spasmolytic effect of citral was observed to be reduced by the nitric oxide synthase inhibitor, L-NAME. In conclusion, citral and the leaf extract of C. citratus exhibited spasmolytic activity and it appeared that they may act as calcium antagonists. Furthermore, the relaxant effect of citral, but not that of the leaf extract may be mediated by nitric oxide suggesting the presence of other chemical components in the leaf extract other than citral.

Cymbopogon citratus has been shown to have antioxidant, antimicrobial, antispasmodic and chemo-protective properties. Citral, is the major constituent of C. citratus. This study investigated the effects of methanolic extracts of leaves (LE), stems (SE), and roots (RE) of C. citratus and citral on vascular smooth muscle and explored their possible mechanisms of action. The experiment was conducted using isolated tissue preparations, where citral, LE, SE, and RE were added separately into a tissue bath that contained aortic rings, which were pre-contracted with phenylephrine (PE). Citral, LE, and RE exhibited a dose-dependent relaxant effect on the PE-induced contractions. Citral appeared to partially act via NO as its vasorelaxant effect was attenuated by L-NAME. However, the effect of LE may involve prostacyclin as indomethacin reversed the relaxant effect of LE on the PE-induced contraction. Furthermore, citral, LE, and RE abolished the restoration of PE-induced contraction caused by the addition of increasing doses of calcium in both endothelium intact and denuded rings. These findings suggest that the relaxation effect of citral, LE, and RE is endothelium-independent and may be mainly by affecting the intracellular concentration of calcium. Citral may partially act through the NO pathway while a vasodilator prostaglandin may mediate the effect of LE.

Background: According to WHO, 1.6 million deaths are caused by pneumococcal infections every year with 0.7 to 1 million in children younger than 5 years mostly in Asia and Africa. Like other gram positive bacteria, Streptococcus pneumoniae is increasingly difficult to treat due to the irrational use of antibiotics. Antimicrobial peptides (AMPs) represent a possible alternative for current antibiotics against drug resistant pathogens. Methods & Materials: In this study, thirteen antimicrobial peptides were designed based on two natural peptides indolicidin and ranalexin. the in vitro activity of these peptides was investigated using broth microdilution assay, hemolytic activity assay, time killing assay, and toxicity assay against two cell lines WRL-68 and NL-20. Mechanisms of action of peptides were assessed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), DNA binding assay, and in silico molecular docking against three virulent fators. Results: Our results revealed that four hybrid peptides RN7-IN10, RN7-IN9, RN7-IN8, and RN7-IN6 possess potent antibacterial activity against 30 pneumococcal clinical isolates (MIC 7.81-15.62g/ml). These four hybrid peptides showed broad spectrum antibacterial activity (7.81g/ml) against S. aureus, methicillin resistant S. aureus (MRSA), and E. coli. Furthermore, the time killing assay results indicated that the hybrid peptides were able to eliminate S. pneumoniae within less than one hour which is faster than the standard drugs erythromycin and ceftriaxone. The cytotoxicity was tested against human erythrocytes, WRL-68 normal liver cell line, and NL-20 normal lung cell line. The results revealed that none of the thirteen peptides have cytotoxic or hemolytic activities at their MICs. TEM and SEM results showed that these four peptides are killing the bacteria by destroying the integrity of thier membranes. DNA binding assay evealed that the hybrid peptides were able to bind to DNA at 62.5 g/ml preventing it from migration through the agarosre gel. The effect of hybrid peptides on the integrity of bacterial membranes