No abstract

The leaves of Aquilaria spp. promote “physiological balance”, and are “cardiotonic and provide blood nourishment”. In Asia, these leaves are increasingly consumed as tea and claimed to provide benefits to cardiovascular function, albeit without any scientific proof. Therefore, this study sought to evaluate the action of Aquilaria crassna leaf aqueous extract (AE) on vascular function and vascular smooth muscle cytotoxicity. AE and a main constituent, mangiferin were investigated for their vasorelaxation of rat mesenteric arteries and aortae in vitro . Acute cytotoxicity of AE (0.1–1000 μg/ml) and mangiferin (0.1–100 μM) on rat enzymatically isolated vascular smooth muscle cells was assayed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide. AE dilated rat mesenteric arteries (EC 50 ∼107 μg/ml, E max ∼95%) more than aorta (EC 50 ∼265 μg/ml, E max ∼76%, p < 0.05). AE-induced vasodilation in mesenteric artery was reduced by endothelial removal (EC 50 ∼202 μg/ml, p < 0.05), incubation with endothelial nitric oxide synthase (eNOS) (100 μM, L -NAME) (EC 50 ∼309 μg/ml, p < 0.05), and partly reduced by L-type Ca 2+ channel blockade at higher concentrations. Likewise, mangiferin (1–100 μM) dilated the mesenteric artery more potently than the aorta. However, its maximum relaxation was less than with AE (41% in the mesenteric artery and <10% in the aorta). Isolated vascular smooth muscle cells incubated in AE or mangiferin for 1 h showed no cytotoxicity. Thus, AE is a vasorelaxant while being free of acute cytotoxicity towards vascular smooth muscle, thus potentially ameliorating human vascular dysfunction.

The health benefits of the Aquilaria crassna Pierre ex Lecomte leaf extract (AE) make it very useful as an ingredient in food and pharmaceutical products. Iriflophenone 3,5-C-β-d-diglucoside (1), iriflophenone 3-C-β-d-glucoside (2) and mangiferin (3) are bioactive compounds of AE. We assessed the stability of AE by investigating the thermal degradation kinetics and shelf-life (t90%) of compounds 1, 2 and 3 using Arrhenius plot models and studied their pH-rate profiles. The results demonstrate that 1 and 2 were degraded, following a first-order kinetic reaction. The degradation of 3 followed first-order reaction kinetics when present in a solution and second-order reaction kinetics in the dried powder form of the extract. According to the first-order kinetic model, the predicted shelf-life (t90%) of the extract at 25 °C in dried form for compound 1 was 989 days with activation energy 129.86 kJ·mol−1, and for 2 it was 248 days with activation energy 110.57 kJ·mol−1, while in the extract solution, the predicted shelf-life of compounds 1–3 was 189, 13 and 75 days with activation energies 86.83, 51.49 and 65.28 kJ·mol−1, respectively. In addition, the pH-rate profiles of 1–3 indicated that they were stable in neutral to acidic environments.

Thermal degradation of verbascoside (VB) in Acanthus ebracteatus Vahl (AE) always affects its health benefit. Here the temperature effect on VB in both AE extract and solid lipid nanoparticles (SLNs)-encapsulated AE extract was demonstrated using the Arrhenius plot. The reaction rate constants were calculated for shelf life and plotted to obtain pH−rate profiles. VB degradation was a first-order reaction. The reaction rate in a neutral to alkaline solution was faster than in an acidic solution. VB in AE extract-loaded SLNs was more stable than in uncapped AE extract. The shelf life of VB in SLNs was 153 days with activation energy (E a ) of 76.16 kJ mol −1 , whereas those of VB in AE extract and in AE extract solution were 75 days with E a = 78.03 kJ mol −1 and 12 days with E a = 49.24 kJ mol −1 , respectively. Therefore, we anticipate that the AE extract-loaded SLNs will be beneficial for product development.