Faculty of Applied Sciences

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Identification of flavonoid C-glycosides as promising antidiabetics targeting protein tyrosine phosphatase 1B
(Hindawi Limited, 2022-06-24) Rampadarath, Athika; Balogun, Fatai Oladunni; Pillay, Charlene; Sabiu, Saheed
Protein tyrosine phosphatase 1B (PTP1B), a negative regulator of the insulin signaling pathway, has gained attention as a validated druggable target in the management of type 2 diabetes mellitus (T2DM). The lack of clinically approved PTP1B inhibitors has continued to prompt research in plant-derived therapeutics possibly due to their relatively lesser toxicity profiles. Flavonoid C-glycosides are one of the plant-derived metabolites gaining increased relevance as antidiabetic agents, but their possible mechanism of action remains largely unknown. This study investigates the antidiabetic potential of flavonoid C-glycosides against PTP1B in silico and in vitro. Of the seven flavonoid C-glycosides docked against the enzyme, three compounds (apigenin, vitexin, and orientin) had the best affinity for the enzyme with a binding score of -7.3 kcal/mol each, relative to -7.4 kcal/mol for the reference standard, ursolic acid. A further probe (in terms of stability, flexibility, and compactness) of the complexes over a molecular dynamics time study of 100 ns for the three compounds suggested orientin as the most outstanding inhibitor of PTP1B owing to its overall -34.47 kcal/mol binding energy score compared to ursolic acid (-19.24 kcal/mol). This observation was in accordance with the in vitro evaluation result, where orientin had a half maximal inhibitory concentration (IC₅₀) of 0.18 mg/ml relative to 0.13 mg/ml for the reference standard. The kinetics of inhibition of PTP1B by orientin was mixed-type with V _max and K _m values of 0.004 μM/s and 0.515 μM. Put together, the results suggest orientin as a potential PTP1B inhibitor and could therefore be further explored in the management T2DM as a promising therapeutic agent.
An investigation of the voltammetric behaviour of antioxidants in flavonoids
(2020-04) Ramsarup, Lee-Ann; Bisetty, Krishna; Kanchi, Suvardhan
The two case studies in this work involve the development and fabrication of an electrochemical biosensor using various enzymes for the evaluation of the electrochemical responses, relating to the total phenolic (TP) content and the antioxidant activities in wine and tea samples respectively. The modification of the glassy carbon electrode (GCE) was carried out using green apple as an enzymatic source of polyphenol oxidase and laccase enzyme. The experimental variables were optimized using the Box-Behnken experimental design as a predictive model, for a better understanding of the parameters and their interaction responses with each other during an electrochemical analysis. This multivariate optimization method is based on a factorial design, where the three most influential factors include the electrolyte pH, the deposition time (td) and the scan rate (sr). The design was run in a single block fashion while random order of experiment was selected to provide greater protection against the effects of outlying variables. The optimized results obtained yielded the most suitable conditions for the determination of the TP content in wine samples. They were selected as follows: phosphate buffer of pH 7.65 as supporting electrolyte, td 29.8 s and sr 25.0 mV/s respectively. The method was optimized for the current signal at a deposition potential of 0.2 V and within an oxidation potential of -0.2 V to 0.6 V. Good analytical responses were obtained with apple sensors for the detection of TP content in wine samples, with a higher concentration in red wines than in white wines. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were used to establish and interpret the redox mechanisms of flavonoids present in alcoholic and non-alcoholic beverages. The sensor responses were evaluated by first, investigating the changes in the total phenolic (TP) content in wine samples using catechin as a standard. Thereafter, the electrochemical behaviour of rutin and ascorbic acid, antioxidant capacities (trolox reagents) were established in tea samples, yielding a positive linear correlation between the trolox equivalent antioxidant capacities (TEAC) and TP content (R2 = 0.9812 ± 0.012). DPV was applied to the laccase modified GCE, and the experimental results indicate that this sensor shows good reducing properties. The scavenging ability of 2,2’-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) a diammonium salt, was assessed in the sample extracts, which yielded half-maximal effective concentration (EC50) values of 10.80 μg/ml and 11.62 μg/ml for ascorbic acid and rutin respectively. These findings indicated that the experimental design was a convenient method to evaluate the statistical significance of the optimised parameters, and the positive linearity for the TEAC and the TP content confirms the robustness of this methodology.
Food borne bacteria isolated from spices and fate of Cronobacter sakazakii ATCC 29544 in black pepper exposed to drying and various temperature conditions
(Academic Journals, 2013-03-19) Madela, Nokwanda; Ijabadeniyi, Oluwatosin Ademola
The degree of infection of Juniperus procera roots by arbuscular mycorrhiza fungi (AMF) is highly indicative of the response of plants to environmental stress and is affected by the presence of flavonoids in the roots. However, relatively little is known about the relationship between soil textural components (sand, clay, silt content) and the percentage of AMF in the field soil. The aim of this work was to determine the relationship between soil textural components, content of flavonoids and AMF infection in the roots of J. procera. A significant correlation was found between AMF in the roots of J. procera and the soil textural components. A positive or negative correlation depended on each composition of soil texture. A negative correlation was found between the percent of AMF in the roots and the amount of coarse sand, fine sand and clay, while a positive correlation existed between the percent of AMF and silt. The degree of colonization with AMF was higher when the quantity of coarse sand was lower (r = -0.83). Similar trend was also observed with fine sand (r = -0.84), and clay (r = -0.83). On the contrary, root colonization with AMF was higher when the quantity of silt was higher (r = 0.92). This study demonstrated that the proportion of silt in the soil and the amount of flavonoid are strongly and positively correlated with AMF infection in the root of J. procera in Saudi Arabia.

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