ABSTRACT
Aims: Alpha (?)-amylase inhibitors from plants are preferable for type 2 diabetes treatment because of their relative potency and safety. This study examined, in vitro, the inhibitory effect of Anthocleista nobilis leaf extract on starch hydrolysis catalyzed by ? -amylase (extracted from moated sorghum). Place and Duration of Study: Department of Biochemistry (School of Biological Sciences) and Department of Chemistry, School of Physical Sciences, University of Cape Coast, Ghana, between June 2021 and August 2021. Methodology: Leaves of A. nobilis were air-dried, pulverized, and macerated in 70% aqueous ethanol for 72 hrs. The filtrate was concentrated and reconstituted in 0.02M Sodium phosphate buffer (pH 6.9) for further analysis including Phytoconstituents screening. In vitro analysis of ? -amylase activity as well as inhibitory effect of A. nobilis extract on ? -amylase was performed. The Lineweaver-Burk plot was employed in the inhibition analysis to determine the inhibition type, maximum initial reaction rate (Vmax), as well as the Michaelis constant (KM). Results: The percentage inhibition of ?-amylase ranged from 25.0 ± 0.46% - 85.7 ± 2.17% for 0.1mg/mL and 0.9mg/mL of the A. nobilis leaf extract respectively. The mode of ?-amylase inhibition was found from the Lineweaver-Burk plot as mixed noncompetitive. The KM and Vmax were determined as 0.2043 mM and 0.1282 mM/min respectively. In contrast, KM for the control were 0.1537mM and Vmax of 0.09750 mM/min. The inhibition property of A. nobilis could be attributed to its phytochemicals such as flavonoids, saponins, alkaloids, tannins, and terpenoids that were present. Conclusion: Anthocleista Nobilis leaf extract contains certain naturally occurring anti-diabetic compounds and could be explored for treating type 2 diabetic patients. These findings, however, need further work to validate the exact bioactive constituents responsible for the inhibitory effect.
ABSTRACT
Objective: To extract and isolate polysaccharide from Cyclocarya paliurus leaves, characterize its structural features and study its α-glucosidase inhibitory effect. Methods: C. paliurus polysaccharide (CP50) was isolated and purified by water extraction and ethanol precipitation, deproteinization with 732 cation exchange resin and 50% ethanol precipitation. Molecular weight of CP50 was determined by high performance gel permeation chromatography-multiple angle laser light scattering (HPGPC-MALLS), and monosaccharide composition was analyzed by HPLC with PMP (1-phenyl-3-methyl-5-pyrazolone) pre-column derivatization. The structure of CP50 was characterized by methylation, Fourier transform infrared spectroscopy (FT-IR), and proton nuclear magnetic resonance spectrum (1H-NMR), respectively. The α-glucosidase inhibitory effect of CP50 was investigated by PNPG method. Results: The molecular weight of CP50 was 59 000. It contained eight kinds of monosaccharides including galacturonic acid, glucose, galactose, arabinose, mannose, xylose, rhamnose, and glucuronic acid with molar ratio of 29.1:25.6:16.5:9.3:6.7:6.1:4.1:2.6. CP50 was mainly composed of →4) GalA (1→, →4) Glc (1→ and →4) Gal (1→ with branches at C-6 position of galactose. Furthermore, our results showed that CP50 exhibited a potent inhibitory effect on α-glucosidase, and the value of IC50 was determined to be 3.3 μg/mL which was much lower than the anti-type 2 diabetes drug acarbose (193.6 μg/mL). The inhibitory mode belongs to the mixed noncompetitive inhibition. Conclusion: CP50 is a pectin-like acidic polysaccharide with complex structure. Moreover, CP50 possesses better α-glucosidase inhibitory effect and potential value for the drug development and utilization.