Piptadenia stipulacea (Benth) Ducke is a tree of the Caatinga, in Northeast Brazil, popularly known as “Jurema-branca”, “Jurema malícia-da-serra”, “Carcará” and “Calumbi”. In folk medicine, a decoction or tincture of its bark and leaves are used to treat wounds and as healing agents. Galetin 3,6-dimethyl ether (FGAL) is a flavonoid isolated from the aerial components of Piptadenia stipulacea (Benth) Ducke. We decided to investigate a possible FGAL spasmolytic effect on preparations of both the guinea pig ileum and trachea, the rat uterus and the male rat aorta. FGAL inhibited oxytocin (IC₅₀ = 2.2 ± 0.4 × 10^–5 M) and carbachol (CCh)-induced (IC₅₀ = 7.7 ± 1.3 × 10^–5 M) phasic contractions in the rat uterus, but was more effective in the inhibition of the oxytocin-induced contractions. In the guinea pig ileum, FGAL equipotently inhibited CCh (IC₅₀ = 2.8 ± 0.4 × 10^–5 M) and histamine-induced (IC₅₀ = 2.3 ± 0.5 × 10^–5 M) phasic contractions. FGAL equipotently and concentration-dependently relaxed guinea pig trachea preparations pre-contracted with CCh, both in the absence (EC₅₀ = 0.8 ± 0.1 × 10^–5 M) and presence (EC₅₀ = 1.0 ± 0.1 × 10^–5 M) of a functional epithelium. FGAL also relaxed preparations of the rat aorta pre-contracted with phenylephrine in both the absence (EC₅₀ = 5.0 ± 1.1 × 10^–6 M) and presence (EC₅₀ = 5.4 ± 1.2 × 10^–6 M) of a functional endothelium. FGAL shows a non-selective spasmolytic effect on each of the smooth muscle preparations we have tested, but with a greater effect on those from the rat aorta. The relaxant effect on preparations of both the guinea pig trachea and the rat aorta seems to not involve the epithelium or endothelium-derived relaxing factors.

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The effects of cooling (to 28°C) were studied on the responses induced by carbachol (10^–9 – 3 × 10^–4 M) and serotonin (5-HT, 10^–8 – 3 × 10^–4 M) in calf cardiac vein preparations and the role of calcium ions in these effects were analyzed. Ring preparations of veins obtained from calf hearts were suspended in organ baths containing 25 mL of Krebs-Henseleit solution, maintained at 37°C and continuously gassed with 95%O₂–5%CO₂. After a resting period, preparations were contracted with carbachol (10^–9 – 3 times; 10^–4 M) and 5-HT (10^–8 – 3 times; 10^–4 M) at 37°C. The same protocol was repeated at 28°C after the preparations were allowed to equilibrate at this temperature for 60 min. In order to analyze the role of calcium ions (Ca²⁺) in the cooling-induced vascular response, concentration-response curves to carbachol and 5-HT were obtained in the presence of verapamil (10^–6 M), caffeine (3 times; 10^–4 M), and Ca²⁺ free medium in the presence of EGTA at 28°C. During cooling to 28°C, the EC₅₀ values, to carbachol and 5-HT were significantly higher than at 37°C. Cooling to 28°C in the presence of verapamil, caffeine or Ca²⁺ free medium in the presence of EGTA increased the EC₅₀ values, to both carbachol and 5-HT. These results suggest that Ca²⁺ plays an essential role in the cooling-induced changes of calf cardiac vein preparations treated with carbachol and 5-HT.

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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-Ca²⁺-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.

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