Table 1.
Yields of total TN extracts and methanol fractions (% w/w), total phenolic content, and antioxidant activity.
Fig 1.
α-Glucosidase inhibitory activity of TN extracts.
(a) α-Glucosidase inhibitory effect of different TN extracts compared to acarbose. A concentration of 10 μg/mL of TN extracts or acarbose was used in this assay. Results are expressed as percentage inhibition relative to the control without inhibitor. Mean values are presented and bars represent standard deviations (n = 3). (b) Concentration-dependent inhibition of TNW, TN50E, TNW30M, and TNW40M compared to acarbose.
Table 2.
α-Glucosidase inhibitory effect (IC50) of different TN extracts compared to acarbose.
Fig 2.
Lineweaver-Burk plot of TN extracts inhibitory activity.
Lineweaver-Burk plot in the absence (black) and presence of IC50 (μg/mL) equivalent of Acarbose (green), TNW (orange) and TN50E extract (red). V0 represents the initial rate of the reaction and [S] the concentration of pNPG in the reaction.
Table 3.
Kinetic parameters of α-glucosidase inhibition in absence and presence of T. nilotica extracts (TNW or TN50E) compared to acarbose.
Fig 3.
Reversibility of α-glucosidase inhibition and effect of pre-incubation.
(a) Reversibility of α-glucosidase inhibition determined by rapid dilution assay. Produced pNP (mM) was determined after incubation of the enzyme in the absence (no inhibitor) or presence of TN50E extract. Initial rates were measured for 15 min after dilution of the enzyme-inhibitor complex with substrate to initiate the reaction. (b) α-glucosidase inhibition in the presence of IC50, IC50/2 and IC50/4 (μg/mL) of TN50E extract or acarbose before and after 1 h of pre-incubation with inhibitor. Mean values are presented and bars represent standard deviations.
Fig 4.
Thermal and pH stability of TN extracts.
(a) pH stability of TN extracts (TNW and TN50E) compared to acarbose. Extracts were incubated at pH 3, 7.5 and 8 for 4 h at 37°C and their inhibitory effect was determined in the standard assay (pH 6.8). (b) Thermal stability of TN extracts (TNW and TN50E) compared to acarbose. Extracts were incubated at room temperature (RT), 37°C and 50°C for 4 h their inhibitory effect was determined in the standard assay (37°C). Mean values are presented and bars represent standard deviations.
Fig 5.
Multivariate analysis of phytochemicals identified in TNW, TN50E extracts and methanolic fractions.
(a) Score plot of PCA analysis comparing TNW (green) and TN50E (red) extracts. (b) Score plot of PCA analysis comparing TNW methanolic fractions. MetaboAnalyst software was used to perform the analysis.
Fig 6.
Molecules contributing to the difference between TNW and TN50E.
Identified phytoconstituents whose relative abundance are significantly different between TNW and TN50E extracts (p value < 0.01). The chemical classifications and sub-classifications are presented for each metabolite.
Table 4.
Compounds with significantly higher abundance in TNW30M/TNW40M and TNW70M/TNW80M compared to TNW10M/TNW60M fractions.