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Leaf Extracts of Aerva lanata Inhibit the Activities of Type 2 Diabetes-Related Enzymes and Possess A 时间:2018-09-27 09:32 来源:未知作者:admin 点击: 次 Abstract:The leaves of Aerva lanata are one of the indigenous medicinal plants used in the management of diabetes mellitus and its associated complications in Africa. However, its effect on the activities of diabetes-related enzymes has not been investigated. This study evaluated the in vitro inhibitory effects of different extracts of the A. lanata leaf on the activities of diabetes-related enzymes (α-amylase and α-glucosidase) and chemically induced free radicals. Aqueous, ethanol, and hydroethanol extracts of A. lanata leaves were subjected to a standard enzyme inhibition assay followed by determination of modes of inhibition of the enzymes. The antioxidant activities of the extracts were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). The results obtained showed that the hydroethanol extract of the A. lanata leaf optimally inhibited both α-amylase (IC50: 2.42 mg/mL) and α-glucosidase (IC50: 0.23 mg/mL). The Lineweaver-Burk plot revealed that the mode of inhibition of both enzymes by the hydroethanol extract was uncompetitive. However, the hydroethanol and aqueous extracts displayed the best DPPH and ABTS radical-scavenging ability, respectively. It can be concluded that the A. lanata extract inhibited the activities of both α-amylase and α-glucosidase uncompetitively, which may be attributed to its free radical-scavenging properties and rich phenolic composition.
1. Introduction
Diabetes is one of the global health emergencies of the 21st century, which affects about 425 million people worldwide, and this may rise up to 629 million by the year 2045 [1]. Type 2 diabetes is the commonest form of this disease which is characterized by insulin resistance or reduced insulin sensitivity leading to hyperglycemia [2]. Management of type 2 diabetes normally entails lifestyle modification (diet and exercise) as well as treatment with oral hypoglycemic drugs, such as insulin secretagogues (e.g., glimepiride) to stimulate insulin secretion, biguanides (e.g., metformin) to decrease hepatic glucose output, thiazolidinediones (e.g., rosiglitazone) to improve insulin sensitivity, and alpha-glucosidase inhibitors (e.g., acarbose) to reduce starch and sucrose digestion [3].
Diabetes and some other diseases like cancer and stroke have been linked to oxidative stress which arises from the excessive production of free radicals in the mitochondrial electron transport chain [4]. Though the natural defence mechanism of animals detoxifies these free radicals with the aid of antioxidant molecules and enzymes, oxidative stress occurs when the effect of free radicals outweighs that of the cellular antioxidants [5]. Therefore, searching for antioxidant and antidiabetic agents from plants is an important strategy required to mitigate the widespread nature of diabetes. This is because present synthetic drugs have many drawbacks ranging from limited efficacy to several side effects such as hypoglycemia, weight gain, and chronic tissue damage.
Aerva lanata (Linn.) Juss. Ex Schult. (Amaranthaceae) is an erect or prostrate plant found in the tropical regions of Africa, India, Arabia, and the Philippines [6]. Commonly referred to as “ewe aje” in the western part of Nigeria and “polpala” in India, the plant enjoys extensive usage in traditional medicine. Different parts of the plant have been used in the treatment of several diseases including inflammation, malaria, kidney stone, rheumatism, bronchitis, haemorrhage, diuresis, jaundice, and diabetes [7]. The plant is very rich in phenolic compounds and alkaloids as well as steroids. Some of the isolated compounds include kaempferol, tiliroside, β-sitosterol, aervoside, syringic acid, and canthin-6-one [8]. A plethora of studies have reported the pharmacological potentials of Aerva lanata ranging from hepatoprotective, anti-inflammatory, antimicrobial, antihelminthic, and antitumour activities to antidiabetic activities [9].