Sabiu S, O'Neill F H, Ashafa A O T
Phytomedicine and Phytopharmacology Research Group, Department of Plant Sciences, University of the Free State, QwaQwa Campus, Phuthaditjhaba 9866, South Africa; Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
J Ethnopharmacol. 2016 May 13;183:1-8. doi: 10.1016/j.jep.2016.02.024. Epub 2016 Feb 21.
Corn silk (Zea mays L., Stigma maydis) is an important herb used traditionally in many parts of the world to treat array of diseases including diabetes mellitus. Inhibitors of α-amylase and α-glucosidase offer an effective strategy to modulate levels of post prandial hyperglycaemia via control of starch metabolism.
This study evaluated α-amylase and α-glucosidase inhibitory potentials of corn silk aqueous extract. Active principles and antioxidant attributes of the extract were also analysed.
The α-amylase inhibitory potential of the extract was investigated by reacting its different concentrations with α-amylase and starch solution, while α-glucosidase inhibition was determined by pre-incubating α-glucosidase with different concentrations of the extract followed by addition of p-nitrophenylglucopyranoside. The mode(s) of inhibition of the enzymes were determined using Lineweaver-Burke plot.
In vitro analysis of the extract showed that it exhibited potent and moderate inhibitory potential against α-amylase and α-glucosidase, respectively. The inhibition was concentration-dependent with respective half-maximal inhibitory concentration (IC50) values of 5.89 and 0.93mg/mL. Phytochemical analyses revealed the presence of alkaloids, flavonoids, phenols, saponins, tannins and phytosterols as probable inhibitory constituents. Furthermore, the extract remarkably scavenges reactive oxygen species like DPPH and nitric oxide radicals, elicited good reducing power and a significant metal chelating attributes.
Overall, the non-competitive and uncompetitive mechanism of action of corn silk extract is due to its inhibitory effects on α-amylase and α-glucosidase, respectively. Consequently, this will reduce the rate of starch hydrolysis, enhance palliated glucose levels, and thus, lending credence to hypoglycaemic candidature of corn silk.
玉米须（玉米，玉米柱头）是一种重要的草药，在世界许多地区传统上用于治疗包括糖尿病在内的一系列疾病。α-淀粉酶和α-葡萄糖苷酶抑制剂通过控制淀粉代谢，为调节餐后高血糖水平提供了一种有效策略。
本研究评估了玉米须水提取物对α-淀粉酶和α-葡萄糖苷酶的抑制潜力。还分析了提取物的活性成分和抗氧化特性。
通过将提取物的不同浓度与α-淀粉酶和淀粉溶液反应，研究提取物对α-淀粉酶的抑制潜力，而α-葡萄糖苷酶抑制作用则通过将α-葡萄糖苷酶与不同浓度的提取物预孵育，然后加入对硝基苯基吡喃葡萄糖苷来确定。使用Lineweaver-Burke图确定酶的抑制模式。
提取物的体外分析表明，它分别对α-淀粉酶和α-葡萄糖苷酶表现出强效和中度抑制潜力。抑制作用呈浓度依赖性，各自的半数最大抑制浓度（IC50）值分别为5.89和0.93mg/mL。植物化学分析表明，生物碱、黄酮类、酚类、皂苷、单宁和植物甾醇可能是抑制成分。此外，提取物能显著清除活性氧，如DPPH和一氧化氮自由基，具有良好的还原能力和显著的金属螯合特性。
总体而言，玉米须提取物的非竞争性和非竞争性作用机制分别归因于其对α-淀粉酶和α-葡萄糖苷酶的抑制作用。因此，这将降低淀粉水解速率，提高缓解后的血糖水平，从而支持玉米须的降血糖特性。
