Abstract
Recent decades have experienced a sharp increase in the incidence and prevalence of diabetes mellitus. One antidiabetic therapeutic
approach is to reduce gastrointestinal glucose production and absorption through the inhibition of carbohydrate-digesting enzymes such as α-
amylase and α-glucosidase and α-amylase. The aim of the current study was to screen six medicinal plant species, with alleged antidiabetic
properties for α-glucosidase inhibitory activities. Powdered plant materials were extracted with acetone, and tested for ability to inhibit baker's
yeast α-glucosidase and α-amylase activities. The largest mass (440 mg from 10 g) of the extract was obtained from Cassia abbreviata, while
both Senna italica and Mormordica balsamina yielded the lowest mass of the extracts. Extracts of stem bark of C. abbreviata inhibited baker's
yeast α-glucosidase activity with an IC50 of 0.6 mg/ml. This plant species had activity at low concentrations, with 1.0 mg/ml and above
resulting in inhibition of over 70%. The other five plant extracts investigated had IC50 values of between 1.8 and 3.0 mg/ml. Senna italica only
managed to inhibit the activity of enzyme-glucosidase at high concentrations with an IC50 value of 1.8 mg/ml, while Tinospora fragosa extracts
resulted in about 55% inhibition of the activity of the enzyme at a concentration of 3.5 mg/ml, with an estimated IC50 value of 2.8 mg/ml.
The bark extract of C. abbreviata was the most active inhibitor of the enzyme, based on the IC50 values (0.6 mg/ml). The bark extract of C. abbreviata
contains non-competitive inhibitor(s) of α-glucosidase, reducing Vmax value of this enzyme from 5 mM·s–1 to 1.67 mM·s–1, while Km remained
unchanged at 1.43 mMfor para-nitrophenyl glucopyranoside. Antioxidant activity of the extracts was also investigated. The C. abbreviata extract was
more active as an antioxidant than the positive control, trolox. The extracts did not inhibit alphaamylase activity more than about 20% at the highest
concentration tested.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:tut/oai:encore.tut.ac.za:d1001248 |
| Date | 09 March 2010 |
| Creators | Shai, LJ, Eloff, JN, Boaduo, N, Mogale, AM, Magano, SR, Mokgotho, MP, Masoko, P |
| Publisher | Elsevier |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | |
| Rights | © 2010 SAAB |
| Relation | South African Journal of Botany |
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