In vitro study on α-amylase inhibitory activity of an Ayurvedic medicinal plant, Anacyclus pyrethrum DC root

Sir,

Diabetes mellitus (DM) consists of a group of metabolic diseases characterized by inappropriate hyperglycemia resulting from defects in insulin secretion, insulin action or both. Perhaps food habits and genetic factors play a major role for diabetes. A study revealed that urbanization of rural India has doubled the rate of diabetes, in which type 2 DM is the primary threat to human health due to the increasing prevalence, chronic course and disabling complications.[1] The medicinal plants or natural products involve retarding the absorption of glucose by inhibiting the carbohydrate hydrolyzing enzymes, such as pancreatic amylase. The inhibition of this enzyme delays carbohydrate digestion and prolong overall carbohydrate digestion time, resulting in the reduction in glucose absorption rate and consequently dulling the postprandial plasma glucose rise. Several indigenous medicinal plants have high potential in inhibiting α-amylase enzyme activity.[2] Different parts of plant have been used predominantly in folk medicine worldwide for the treatment of various diseases such as paralysis, epilepsy, fever, pharyngitis, tonsillitis, and diabetes.[3] However, their antidiabetic activity has not been documented. This study was carried out to evaluate in vitro inhibitory effects of various extracts (petroleum ether, chloroform, ethyl acetate, acetone, ethanol, and water) of A. pyrethrum root on porcine pancreatic amylase activity.

The species for the proposed study, A. pyrethrum DC root was purchased from local market (M.A.S. Stores, Country drugs wholesale and retail, Erode, India) and authenticated by Prof. P. Jayaraman, Director, National Institute of Herbal Science, Chennai-45, (Ref. no: PARC/2011/896). The dried powdered plant root of A. pyrethrum DC was extracted using a soxhlet apparatus sequentially with petroleum ether, chloroform, ethyl acetate, acetone, ethanol, and water. Each extract was evaporated using rotary evaporator under reduced pressure. The preliminary phytochemical screening of extracts was carried out by chemical tests.[4] The dried extracts were dissolved in dimethyl sulfoxide to make different concentrations and subjected to α-amylase inhibitory assay[5] and the results were tabulated [Table 1].

Table 1.

α-amylase inhibitory effects of different extracts of Anacyclus pyrethrum DC root

In comparison of IC₅₀ value of α-amylase inhibitory effect of different extracts of A. pyrethrum DC root against porcine pancreatic amylase revealed that ethanol extract at higher concentration showed 88.26% (IC₅₀-29.25 μg/ml) significant α-amylase inhibitory effect than the other extracts. Simultaneously, all extract showed appreciable α-amylase inhibitory activity except petroleum ether extract when compared with acarbose. It may be due to the presence of chemical constituents such as alkaloids, flavonoids, phytosteroids, and also glycosides. The plant-based α-amylase inhibitory offers a prospective therapeutic approach for the management of diabetes.[6] This study supports the Ayurvedic concept that A. pyrethrum DC root could be useful in management of diabetes.[7] Furthermore, the in vivo antidiabetic activity of these extracts needs to be assessed prior to clinical use.