Anti-polyphenol oxidase properties of total flavonoids from young loquat fruits: inhibitory activity and mechanism.
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ABSTRACT:
SUBMITTER: Huang GL
PROVIDER: S-EPMC8806263 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:In this study, a polydopamine (PDA)-modified hollow fiber-immobilized xanthine oxidase (XOD) was prepared for screening potential XOD inhibitors from flavonoids. Several parameters for the preparation of PDA-modified hollow fiber-immobilized XOD, including the dopamine concentration, modification time, XOD concentration and immobilization time, were optimized. The results show that the optimal conditions for immobilized XOD activity were a dopamine concentration of 2.0 mg/mL in 10.0 mM Tris-HCl buffer (pH 8.5), a modification time of 3.0 h, an XOD concentration of 1000 μg/mL in 10.0 mM phosphate buffer (pH 7.5) and an immobilization time of 3.0 h. Subsequently, the enzymatic reaction conditions such as the pH value and temperature were investigated, and the enzyme kinetics and inhibition parameters were determined. The results indicate that the optimal pH value (7.5) and temperature (37 °C) of the PDA-modified hollow fiber-immobilized XOD were consistent with the free enzyme. Moreover, the PDA-modified hollow fiber-immobilized XOD could still maintain above 50% of its initial immobilized enzyme activity after seven consecutive cycles. The Michaelis-Menten constant (Km) and the half-maximal inhibitory concentration (IC50) of allopurinol on the immobilized XOD were determined as 0.25 mM and 23.2 μM, respectively. Furthermore, the PDA-modified hollow fiber-immobilized XOD was successfully applied to evaluate the inhibitory activity of eight flavonoids. Quercetin, apigenin, puerarin and epigallocatechin showed a good inhibition effect, and their percentages of inhibition were (79.86 ± 3.50)%, (80.98 ± 0.64)%, (61.15 ± 6.26)% and (54.92 ± 0.41)%, respectively. Finally, molecular docking analysis further verified that these four active compounds could bind to the amino acid residues in the XOD active site. In summary, the PDA-modified hollow fiber-immobilized XOD is an efficient method for the primary screening of XOD inhibitors from natural products.
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Project description:Loquat fruits are known to have high nutritional contents and phytochemicals which are attributed with its health benefits. However, its storage life is reported to be very limited which negatively affect its marketability and consumption. Present study aimed to investigate the influence of seven different bio-materials or the combination of bio-materials on the postharvest life and storage quality of loquat (Eriobotrya japonica Lindl.) fruits var. 'Morphitiki'. The tested bio-materials or the combinations of current works was (1) OFI-Oputia ficus-indica extract; (2) OFI + Ns-Oputia ficus-indica extract + Nigella sativa oil; (3) OFI + PEx-Oputia ficus-indica extract + propolis extract; (4) OFI + C-Oputia ficus-indica extract + cinnamon oil; (5) Ns-Nigella sativa oil; (6) PEx-propolis extract and (7) CcEx-Chrysanthemum coronarium flower extract. As expected, weight loss showed an increasing tendency during storage period. Results showed that all of the tested bio-materials were effective in maintaining the postharvest quality of loquat fruits by reducing weight loss, positively affecting fruit firmness, preventing fruit browning and reducing decay incidence. Results suggested that loquat fruits can be stored with an acceptable quality for up to 35 days at 4 ± 1 °C and 95% relative humidity conditions, when treated with 0.5% Nigella sativa oil (Ns) or 0.5% propolis extract (PEx).
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Project description:BackgroundGlycation of serum albumin and its consequence products were considered as an important factor in drug distribution and diabetic complications, therefore finding the glycation inhibitors and their inhibitory mechanisms became a valuable field of study. In this work, bovine serum albumin (BSA) became a subject as a model protein for analyzing the inhibitory mechanism of flavonoids, known as natural BSA glycation inhibitors in the early stage of glycation.MethodsFirstly, for theoretical study, the three-dimensional model of BSA structure was generated by homology modeling and refined through molecular dynamic simulation. Secondly, several validation methods (statistical assessment methods and also neural network methods) by simultaneous docking study were employed for insurance about accuracy of our simulation. Then docking studies were performed for visualizing the relation between flavonoids' binding sites and BSA glycation sites besides, the correlation analyzes between calculated binding energy and reported experimental inhibitory IC50 values of the flavonoids set, was considered to explore their molecular inhibitory mechanism.ResultsThe quality assessment methods and simultaneous docking studies on interaction of quercetin (as the most studied flavonoids) with BSA and Human serum albumin (HAS), confirm the accuracy of simulation and the second stage of docking results which were in close agreement with experimental observations, suggest that the potential residues in flavonoids binding sites (which were place neighbor of tryptophan 212 within 5Ǻ) cannot be considered as one of glycation sites.ConclusionsBased on the results, flavonoids don't participate in inhibitory interference mechanism, and also, the differentiation between complexes of flavonoids with BSA and HSA could destroy the speculation of using them as an exchangeable model protein in study of serum albumin and flavonoids interactions.
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