Antidiabetic potential of methanol extracts from leaves of Piper umbellatum L. and Persea americana Mill.

Objective: To determine inhibitory activity of methanolic leaf extract of Piper umbellatum and Persea americana(P. americana)(traditionally used in Cameroon against diabetes) on β-glucosidase, β-glucosidase, maltase-glucoamylase, aldose reductase and aldehyde reductase activities, enzymes involved in starch digestion or diabetic complications. Methods: The methanol extracts from Piper umbellatum and P. americana were prepared by maceration. To assess relative efficacy of these extracts, the determination of concentrations that were needed to inhibit 50% of enzyme activity was done, whereas, gas chromatography-mass spectrum was used to identify components from extracts that may be responsible for the activities. Results:The tested extracts strongly inhibited β-glucosidase, maltase-glucoamylase, aldose reductase and aldehyde reductase activities with IC50 ranging from(1.07 ± 0.03) to(31.77 ± 1.17) μg/mL.Among the tested extracts, P. americana was the most active against sensitive enzymes(IC50 of1.07 ± 0.03 to 15.63 ± 1.23). But, none of the extracts showed interesting inhibitory effect against β-glucosidase as their percentage inhibitions were less than 16%. From gas chromatographymass spectrum analysis, 10 and 8 compounds were identified in Piper umbellatum and P.americana extracts respectively, using NIST library 2014. Conclusions: Results of this study provide the scientific credential for a prospective usage of these plants to treat diabetes.

Longitudinal and lateral slip control of autonomous wheeled mobile robot for trajectory tracking

研究目的:轮式机器人广泛应用于自主移动机器人研究。已有文献大多数将机器人抽象成具备非完整约束的机械模型,这一假设条件仅在机器人低速运动时成立。本文考虑四轮机器人,同时考虑其纵向和侧向滑动控制,与实际情况更贴近。创新要点:针对轮式移动机器人模型,同时考虑纵向和侧向滑动分量。研究方法:设计纵向滑行控制策略(图1)。改变自然频率(图4)、阻尼和质量(图5)、轮子半径(图6)分别测试控制器响应,最终获取最优控制参数(表2)。重要结论:仿真结果验证所提控制策略的有效性。通过测试选择合适参数使控制器实现快速平滑响应。所设计的控制器对轮子滑动扰动不作限制性假设,即可实现误差指数收敛。