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Vasodilatory effects of mulberry leaf extract (MLE) and its possible underlying mechanisms on porcine basilar artery (PBA) were investigated by measuring changes in isometric tension in vitro. MLE slightly relaxed 60 mM KCl pre-contracted PBA rings (9.4% at 540 μg/mL). A treatment with MLE induced extensive relaxation under pre-contraction with 0.1 μM U-46619 (EC50 = 49.4 μg/mL). Neither endothelial denudation nor treatment with atenolol (10 μM) affected MLE-induced relaxation. Relaxation induced by MLE (540 μg/mL) was significantly attenuated by cimetidine (10 μM). MLE inhibited angiotensin I-induced contraction in endothelium-intact PBA rings (EC50 = 25 μg/mL), similar to captopril. Therefore, the possible mechanisms underlying MLE-induced relaxation in PBA might be mediated through: (1) functional antagonism of thromboxane A2 receptors; (2) suppression of angiotensin I-induced contraction; (3) Ca2+ influx inhibition; (4) stimulation of H2-receptors. Moreover, MLE contained significant amounts of nitrite, nitrate and several phenolic compounds, possibly associated with MLE-induced relaxation.

Vasodilatory effects of mulberry leaf extract (MLE) and its possible underlying mechanisms on porcine basilar artery (PBA) were investigated by measuring changes in isometric tension in vitro . MLE slightly relaxed 60 mM KCl pre-contracted PBA rings (9.4% at 540 μg/mL). A treatment with MLE induced extensive relaxation under pre-contraction with 0.1 μM U-46619 (EC 50 = 49.4 μg/mL). Neither endothelial denudation nor treatment with atenolol (10 μM) affected MLE-induced relaxation. Relaxation induced by MLE (540 μg/mL) was significantly attenuated by cimetidine (10 μM). MLE inhibited angiotensin I-induced contraction in endothelium-intact PBA rings (EC 50 = 25 μg/mL), similar to captopril. Therefore, the possible mechanisms underlying MLE-induced relaxation in PBA might be mediated through: (1) functional antagonism of thromboxane A 2 receptors; (2) suppression of angiotensin I-induced contraction; (3) Ca 2+ influx inhibition; (4) stimulation of H 2 -receptors. Moreover, MLE contained significant amounts of nitrite, nitrate and several phenolic compounds, possibly associated with MLE-induced relaxation. [ABSTRACT FROM AUTHOR]

Abstract: The effects of sample preparation, cultivar, leaf age and tea processing on melatonin content of mulberry (Morus spp.) leaves were investigated. Sample preparation using ultrasonic technique in combination with solid phase extraction resulted in high recovery rate (76%), when compared to homogenisation in combination with liquid–liquid extraction procedure (12% recovery rate). The melatonin contents in mulberry leaves harvested from three major cultivars (Buriram 60, Sakonnakhon and Khunphai) grown in Thailand were identified and quantified using high-performance liquid chromatography combined with fluorescence detector. The average melatonin content of the mulberry leaves cv. Buriram 60 (279.6ng/g dry weight (DW)) was higher than those of cv. Sakonnakhon (100.5ng/g DW) and cv. Khunphai (40.7ng/g DW). The melatonin contents of all cultivars tested were highest in the tip of the leaves, followed by that in the young leaves, whereas the lowest was found in the old leaves. The melatonin contents of the two types of tea produced from mulberry leaves cv. Buriram 60 were also determined. Heat treatment during tea processing decreased the melatonin content in mulberry leaves cv. Buriram 60 by approximately 87%, when compared to that of the fresh leaves. However, there were no significant differences between the melatonin contents of the mulberry leaf tea produced with blanching (mulberry green tea) and those produced without blanching (mulberry black tea). [Copyright &y& Elsevier]