Number Of Phenolic Hydroxyl Groups Research Articles

Exploring the relationship between lignin structure and antioxidant property using lignin model compounds

Lignin has a natural polyphenol structure that is expected to replace chemically synthesized antioxidants as a native antioxidant with biodegradable and convenient source characteristics. However, the improvement of the antioxidant property of lignin and its application as an antioxidant are still somewhat limited due to the lack of understanding of the relationship between specific lignin structures and antioxidant property. Therefore, the study of the relationship between lignin structure and antioxidant property is crucial to realize the high-quality application of lignin. In this experiment, the scavenging ability of free 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radicals was determined for different grades of acetylated tannins, typical lignin model compounds and different structural units of milled wood lignin to investigate the relationship between lignin structure and antioxidant property. Based on the experimental results, some structure-activity relationships were proposed and the mechanism of the antioxidant property of lignin was discussed. The number of phenolic hydroxyl groups was linearly and positively correlated with antioxidant property, and the scavenging of DPPH radicals increased significantly with the increase in the number of methoxy groups in the model compounds. Moreover, aldehyde and carboxyl groups had a negative effect on the antioxidant property of lignin, while methoxy, alkyl and alcohol hydroxyl groups played a positive role. The guaiacyl (G) and syringyl (S) units favored the antioxidant property, so the difference in the content of structural units in lignin under certain conditions of phenolic hydroxyl content also affected the antioxidant property. Therefore, the antioxidant property of aspen milled lignin was higher than that of other milled lignin from different wood species. Finally, the mechanism of DPPH free radical scavenging by lignin was revealed to better understand the relationship between lignin structure and antioxidant property.

GPx-like phenolic-amine nanoparticles with onion peel-off model for constantly generative anti-inflammation and anti-oxidation capability

Oxidative stress and inflammation are hallmark characteristics of Atherosclerosis (AS) and are crucial points for treatment. Polyphenolic materials have been widely used in anti-inflammatory and antioxidant therapy due to their naturally excellent antioxidant properties, which are limited by the irreversible depletion of a limited number of phenolic hydroxyl groups under oxidative stress. Therefore, polyphenols alone cannot meet the need for long-lasting anti-inflammatory and antioxidant effects in atherosclerosis. In this work, inspired by the natural antioxidant defense system in living organisms, we introduce the CASe nanoparticle capitalizing on the synergistic action of polyphenols and diselenium. In vitro and in vivo experiments have demonstrated that the incorporation of diselenium not only enhance the reactive oxygen species (ROS) scavenging synergized with polyphenols, but also imparts glutathione peroxidase (GPx)-like activity and in situ nitric oxide (NO) -catalyzed release. In addition, ROS-triggered onion peel-off degradation ensures the continuous generation of refreshed surfaces, endowing CASe with a persistent anti-inflammatory and antioxidant capacity. These features facilitate the long-term treatment of chronic inflammatory diseases, providing a dynamic and effective approach for AS treatment.

Adsorption behavior of self-loading bayberry tannin resin for UO22+ with surface phenolic hydroxyl groups

In this study, self-polymerization of bayberry tannin and formaldehyde condensation were used to prepare a self-loading tannin resin (STR). The environmental conditions for UO22+ capture by STR were thoroughly investigated; the experimental results indicated that the UO22+ adsorption capacity of STR could reach 691.9 mg/g under optimal adsorption conditions. The mechanism of UO22+ capture by STR was studied using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results showed that STR possessed a significant number of phenolic hydroxyl groups, which enabled the reduction of U(VI) in water to U(IV). Subsequently, stable chelation complexes were formed by filling vacant orbitals of uranium through the lone electron pair of oxygen, resulting in the formation of O = U = O structural motifs, which facilitated the effective capture of UO22+ in water. Moreover, the evaluation of the performance of STR in low-concentration UO22+ extraction from seawater revealed its favorable UO22+ removal capacity, even in simulated seawater conditions. These findings highlight the substantial potential of STR for practical applications in uranium remediation.

Highly Efficient Tannic Acid (TA) -Iron Ion (Fe3+) Modification of Polyethylene Terephthalate (PET) Fibers for High-Performance Polymer Composites

The polyethylene terephthalate (PET) fibers surfaces were modified by complexing tannic acid (TA)-iron ions (Fe3+) to form a metal skeleton structure on the fibers. In this system a large number of phenolic hydroxyl groups, epoxy groups and other active groups on the fibers surfaces can stabilize the metal skeleton structure and enhance the interfacial peeling performance between the fibers and the composite rubber matrix. The modified PET fibers were analyzed by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and mechanical properties. The results showed that the peeling strength between the modified fibers and the rubber matrix was increased 45%. This method has the advantages of simple operation, mild conditions and low cost, which provides a new idea for the preparation of rubber/polyester fiber composites with excellent mechanical properties.

α-Glucosidase Inhibitors from Cold-Pressed Black Sesame (Sesamum indicum) Meal: Characterization of New Furofuran Lignans, Kinetic Study, and In Vitro Gastrointestinal Digestion.

Black sesame (Sesamum indicum) meal is an agricultural waste obtained after oil extraction. It is used as a key protein source in animal feed. Previous investigations have indicated that its health benefits, such as antidiabetic activity, are mainly due to its high lignan content. In the present study, we applied α-glucosidase inhibitory guided isolation to identify the active components responsible for the above claim. Twenty-nine compounds, mostly lignans, were isolated and identified, of which five (2-3, 12-13, and 28) were newly isolated. Of the isolated compounds, 20 and 21 were the most potent inhibitors, retarding enzyme function in noncompetitive and uncompetitive manners. Structure-activity relationship analysis suggested that the number of phenolic hydroxyl groups in the structures was significantly related to the inhibitory effect against α-glucosidase. A gastrointestinal digestion study of the major lignan sesaminol triglucoside (STG, 9) suggested that the transformation of dioxymethylene and glucoside moieties gradually began in the late process, thus enhancing the α-glucosidase inhibitory effect.

Interaction mechanism of okra (Abelmoschus esculentus L.) seed protein and flavonoids: Fluorescent and 3D-QSAR studies

The binding capacity of 10 flavonoids with okra seed protein (OSP) was studied by fluorescence spectroscopy. The structure of flavonoids had an obvious impact on binding performance. The binding ability of flavanone was lower than that of flavone, isoflavone and dihydrochalcone. The binding capacity of flavonoid glycoside was superior to that of the corresponding flavonoid aglycone. The binding ability was positively correlated with the number of phenolic hydroxyl groups on the B ring. The steric field and electrostatic field model constructed by 3D-QSAR method could well explain the above interaction behavior. Thermodynamic analysis suggested that the quenching mechanism of OSP caused by flavonoids was static quenching, and the binding-site number was 1. In addition, hydrogen bonding and van der Waals force dominated this interaction. The 3D and synchronous fluorescence spectra showed that there was no significant change in the polarity of the environment around tryptophan and tyrosine residues during binding.

Utilization of self-assembled soy protein nanoparticles as carriers for natural pigments: Examining non-interaction mechanisms and stability

In this study, we made self-assembled soy protein nanoparticles (SPN) by partially hydrolyzing soy protein isolate (SPI) using Flavourzyme at different hydrolysis times (0, 0.5, 1, 1.5, 2, 3, and 4 h). Compared with SPI, SPN (hydrolysis time, 1.5 h) was spherical with smaller particle size, better dispersion, and higher surface hydrophobicity. The interaction and stability of SPN loaded with different concentrations (0, 0.05, 0.1, 0.3, and 0.5 mmol/L) of lutein (Lut), β-carotene (β-Car), and curcumin (Cur) were then characterized. The encapsulation efficiency, load capacity, and X-ray diffraction measurements showed that natural pigments were successfully encapsulated by SPN in amorphous form, with the highest encapsulation efficiency observed at 0.05 mmol/L with 94.3%, 88.7%, and 96.0% for Lut, β-Car, and Cur, respectively. Fluorescence, ultraviolet, and infrared spectroscopy revealed that natural pigments were loaded into SPN mainly by hydrophobic interactions, and hydrogen bonding was also involved in the loading process of Lut and Cur. Moreover, the outcomes of the isothermal titration calorimetry measurement validated the spontaneous and entropy-driven binding process between SPN and natural pigments. Due to its low molecular weight, a high number of phenolic hydroxyl groups, and low spatial resistance, Cur was most encapsulated in SPN, while the strongest interactions were observed. Lut, β-Car, and Cur were encapsulated by SPN with significantly better thermal and light stability, especially Cur. This study may open a new avenue for the use of SPN as product formulations to extend lipophilic natural edible pigments in food products.

Antioxidative Impact of Phenolics-Loaded Nanocarriers on Cytoskeletal Network Remodeling of Invasive Cancer Cells.

Natural phenolic compounds have antioxidant properties owing to their free radical-scavenging capability. The combined effect of a mixture of phenolic compounds has been studied; however, the detailed investigation for finding a correlation between single phenolic molecules and antioxidant activity has not been explored. Herein, we revealed that the number of phenolic hydroxyl groups in phenolics played a central role in their antioxidant capacity. Based on the finding, tannic acid showed the most effective antioxidant potential, e.g., 76% in tannic acid versus 22% in vitamin C as a standard antioxidant component. Because cancer progression is closely related to oxidative processes at the cellular level, we further applied the surface treatment of tannic acid drug-delivery nanocarriers. Tannic acid-loaded nanocarriers reduced reactive oxygen species of cancer cells as much as 41% of vehicle treatment and remodeled cytoskeletal network. By a gelatin degradation study, TA-loaded nanocarrier-treated cells induced 44.6% reduction of degraded area than vehicle-treated cells, implying a potential of blocking invasiveness of cancer cells.

Plant Polyphenols Attenuate DSS-induced Ulcerative Colitis in Mice via Antioxidation, Anti-inflammation and Microbiota Regulation.

The pathogenesis of ulcerative colitis (UC) is associated with inflammation, oxidative stress, and gut microbiota imbalance. Although most researchers have demonstrated the antioxidant bioactivity of the phenolic compounds in plants, their UC-curing ability and underlying mechanisms still need to be further and adequately explored. Herein, we studied the antioxidation-structure relationship of several common polyphenols in plants including gallic acid, proanthocyanidin, ellagic acid, and tannic acid. Furthermore, the in vivo effects of the plant polyphenols on C57BL/6 mice with dextran-sulfate-sodium-induced UC were evaluated and the action mechanisms were explored. Moreover, the interplay of several mechanisms was determined. The higher the number of phenolic hydroxyl groups, the stronger the antioxidant activity. All polyphenols markedly ameliorated the symptoms and pathological progression of UC in mice. Furthermore, inflammatory cytokine levels were decreased and the intestinal barrier was repaired. The process was regulated by the antioxidant-signaling pathway of nuclear-erythroid 2-related factor 2. Moreover, the diversity of the intestinal microbiota, Firmicutes-to-Bacteroides ratio, and relative abundance of beneficial bacteria were increased. An interplay was observed between microbiota regulation and oxidative stress, immunity, and inflammatory response. Furthermore, intestinal barrier repair was found to be correlated with inflammatory responses. Our study results can form a basis for comprehensively developing plant-polyphenol-related medicinal products.

STRUCTURE-ACTIVITY-RELATIONSHIP OF THE POLYPHENOLS INHIBITION OF α-AMYLASE AND α-GLUCOSIDASE

Background: Diabetes mellitus (DM) is a serious public health challenge, projected by WHO to be one of the 7 leading cause of death by 2030. Medicinal plants have been demonstrated to be useful in DM local management because of polyphenols present in these plants. For an alternative treatment approach especially with polyphenols-rich herbs, knowledge of comparative efficacy of the polyphenols will lead to enhanced therapy especially in postprandial hyperglyceamic control. Materials and Methods:Vegetative parts of Anacardium occidentale, Abelmoschus ecsulentus and Ceiba pentandra, prominent in the local management of DM were identified, collected and subjected to alcoholic extraction. From the crude extracts were isolated agathisflavone, quercetin 3-O-glucoside, quercetin 3-O-diglycoside, mangiferin, isomangiferin and pentagalloyl glucose, belonging to flavonoid, xanthones and tannins structural classes. These polyphenols were evaluated for their potentials to inhibit both α-glucosidase and α-amylase. Physicochemical parameters of the polyphenols were evaluated and molecular docking experiments were carried out to gain insight into the observed inhibitory activity. Results: quercetin 3-O-glucosidewas the most potent of the polyphenols against the two enzymes. Increase in the number of phenolic hydroxyl group did not increase the inhibitory activity and neither computation of the binding energies with the enzymes nor physicochemical parameters of the polyphenols could explain the observed inhibitory activity against the enzymes, across the structural classes. Thus, only the bioassay against the enzymes α-glucosidase and α-amylase correlated well with the use of the plants in treating diabetic mellitus Conclusion: Medicinal plants rich in quercetin 3-O-glycoside may have better treatment outcomes in postprandial hyperglycaemia control.

Adsorption-Reduction Behavior of Cr(VI) by Ferrihydrite-Fulvic Acid Complexes with Different C/Fe Mole Ratios

Ferrihydrite and fulvic acid are prevalent components of soils and can significantly influence the environmental behavior of Cr(VI) in these matrices. Prior research has investigated the sorption behavior of Cr(VI) by ferrihydrite and fulvic acid independently; however, the sorption-reduction capacity of Cr(VI) by the ferrihydrite-fulvic acid complex, which is ubiquitously present in soils, has been less explored. In this study, ferrihydrite-fulvic acid complexes (Fh-FA) with varying C/Fe mole ratios were synthesized, and the adsorption-reduction behaviors of Cr(VI) on Fh-FA were examined using batch experiments, FTIR, BET, XRD, SEM-EDS, and XPS. The results demonstrate that the pseudo-second-order kinetic model can accurately describe the adsorption process of Fh-FA on Cr(VI), which can be delineated into three stages: rapid adsorption (0-30 min), slow adsorption (30-120 min), and reaction equilibrium (>120 min). The adsorption of Cr(VI) on Fh-FA primarily occurs through chemisorption. FTIR and XPS analyses revealed that Cr(VI) is initially adsorbed by Fe-OH on the Fh-FA surface. However, as the C/Fe mole ratio of Fh-FA increases, more Fe-OH is complexed by -COOH from FA, resulting in a decrease in the adsorption capacity of Cr(VI) by Fh-FA. The number of phenolic hydroxyl groups from FA also increases, providing additional electrons to reduce Cr(VI) to Cr(III) with increasing C/Fe mole ratio. This study not only emphasizes the adsorption-reduction behavior of Cr(VI) by ferrihydrite-fulvic acid complexes but also uncovers the interplay between C/Fe mole ratios and Cr(VI) adsorption-reduction, contributing to a more comprehensive understanding of the relative roles of Fe hydroxides and natural organic matter in soil environments. These findings have significant implications for Cr(VI) management in soils, enhancing our capability to protect and sustain the environmental quality.

A high-protein retained PES hemodialysis membrane with tannic acid as a multifunctional modifier

A high protein retention polyethersulfone (PES) membrane was prepared by nonsolvent-induced phase separation and surface coating, which exhibited enhanced hemocompatibility and antioxidant stress performance. The cross-linked network was constructed by tannic acid (TA) and alpha-lipoic acid (α-LA) on the surface of the membrane, which controlled the pores to a reasonable size. The enrichment of heparin-like groups on the membrane surface, implemented by “hydrophobic interaction” and “click reaction”, confers anticoagulant properties; the presence of a large number of phenolic hydroxyl groups from TA and the introduction of α-LA allows the modified membranes to intervene in oxidative stress. The hemocompatibility characterizations included plasma recalcification time (PRT), activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT) and hemolysis rate (HR). Additionally, the DPPH ABTS radical scavenging capacity was tested to evaluate the antioxidant performance. The results show that the modified membrane presents an outstanding protein retention rate (99.3%) along with permeability. In addition, the PRT is prolonged to 341.7 s, and the DPPH• scavenging ability reaches 0.74 µmol•cm-2. The membranes can be easily prepared and present excellent comprehensive performance. This work provides a simple and facile strategy for the fabrication of hemodialysis membranes with controllable pore sizes.

Effects of polyphenols on the thermal decomposition, antioxidative, and antimicrobial properties of poly(vinyl alcohol) and poly(vinyl pyrrolidone)

Thermal stabilizers are frequently employed to increase the thermal stability of polymers. Among the thermal stabilizers, the polyphenols and related molecules have been widely used as thermal stabilizers of polymers. However, the effect of the number of their phenolic hydroxyl groups on the thermal decomposition of polymers was relatively less studied. In this study, three phenolic compounds with different numbers of phenolic hydroxyl groups (phenol, pyrocatechol, and pyrogallol) were incorporated in water-soluble poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) to fabricate the polymer/phenolic additive composite films. The effects of the phenolic additive on the thermal decomposition of PVA and PVP were investigated through thermogravimetric analysis. The results suggested that the phenolic additive is effective as a thermal stabilizer, owing to its radical-trapping action, when its boiling point is higher than the thermal decomposition temperature of the polymer (PVA and PVP) and the polymer decomposition follows a radical pathway. In addition, to compare the effect of the number of phenolic hydroxyl groups in the phenolic additive on the properties of the composite films, their antioxidative and antibacterial activities were evaluated using the α,α-diphenyl-β-picrylhydrazyl assay and disk diffusion test, respectively.

Phenolic acids modified cellulose microspheres for selective capture of Bi(III): Batch, column and mechanism investigation

Bismuth (Bi) is a strategic metal, and its recovery is of great significance for environmental protection and resource recycling. In this work, three polyhydroxyl monomers (gallic acid (GA), protocatechuic acid (PC) and shikimic acid (SA)) functionalized cellulose microspheres (MCGA, MCPC and MCSA) were fabricated by radiation technology, and employed for Bi(III) uptake. The effect of the number and type of hydroxyl groups on the adsorption performance was evaluated by batch and column experiments. The adsorption capacity of phenolic acid modified MCGA (Qm = 155.28 mg/g) and MCPC (Qm = 93.46 mg/g) was found to be significantly higher than that of non-phenolic acid modified MCSA (Qm = 3.90 mg/g) in the batch experiment. DFT calculation manifested that the phenolic hydroxyl groups could more easily coordinate with Bi(III) than the alcoholic hydroxyl groups. The higher number of phenolic hydroxyl groups, the more favorable the coordination. Notably, the column experiments demonstrated that MCGA and MCPC can selectively capture and recover Bi(III) using 0.5 M HNO3. Finally, the MCGA and MCPC could remove trace Bi(III) from actual environmental water samples, indicating that MCGA and MCPC would be promising candidates in environmental remediation and water purification.

Interaction Mechanism between OVA and Flavonoids with Different Hydroxyl Groups on B-Ring and Effect on Antioxidant Activity.

Ovalbumin (OVA) is a common carrier with high efficiency to deliver flavonoids. The aim of this study was to investigate the interaction mechanism of OVA and four flavonoids (quercetin (Que), myricetin (Myri), isorhamnetin (Ish), and kaempferol (Kaem)) with similar structures by fluorescence spectra, SDS−PAGE, FT−IR, and molecular docking analysis, and the effect on the antioxidant abilities of flavonoids was also evaluated. Results indicated that the antioxidant activity of flavonoids was positively correlated to the number of phenolic hydroxyl groups of on the B-ring, and weakened when the C-3′ position was replaced by a methoxy group. The addition of OVA enhanced the antioxidant activity of Que/Kaem, while it masked the antioxidant activity of Myri. The formation of Que/Myri/Ish/Kaem−OVA complexes was a spontaneous exothermic process driven mainly by hydrogen bond and van der Waals force, which could result in the change in OVA conformation and induce the transformation of α-helix to β-sheet. Among these, Kaem exhibited the strongest binding ability with OVA, and showed the greatest impact on the secondary and conformational structure of OVA, followed by Que. The hydroxylation of C-3′ and methoxylation of C-5′ weaken the interaction of Kaem with OVA. Molecular docking analysis suggested that Que, Myri, Ish, and Kaem formed six, three, five, and four hydrogen bonds with OVA, and the number of hydrogen bonds was not positively correlated with their binding constants. Our findings can provide a theoretical basis for the application of OVA on improving the antioxidant activity of flavonoids, and may help to explain the delivery efficiency of OVA on different bioactive constituents.

Carrier-Free Deferoxamine Nanoparticles against Iron Overload in Brain

Carrier-Free Deferoxamine Nanoparticles against Iron Overload in Brain

Chemical Derivatization of Commercially Available Condensed and Hydrolyzable Tannins.

Novel valorization routes for tannins were opened by the development of a simple, straightforward, robust, and flexible approach to the selective functionalization of condensed and hydrolyzable tannins. Irrespective of the different degrees of polymerization, different commercial tannins were efficiently functionalized by the generation of an ether linkage bound to a short linker carrying the desired functional group. Functionalizations could be realized at varying degrees of technical loadings, i.e., amounts of introduced tannin-alien functionalities per number of phenolic hydroxyl groups. The same strategy was found suitable for the synthesis of polyethylene glycol-functionalized tannin copolymers. Condensed tannins functionalized with carboxylic acid moieties could be converted into a tannin–oligopeptide hybrid.

Polyphenols separated from Enteromorpha clathrata by one-dimensional coupled with inner-recycling high-speed counter-current chromatography and their antioxidant activities

Algae polyphenols, derived from marine algae, have gained much attention in recent years for their diverse biological activities, such as antibacterial, antioxidant, anti-inflammatory, and cholesterol-lowering effects. Extraction, purification, and identification of individual compounds are difficult due to the broad range of molecular sizes and complex structures. In this paper, an efficient separation of polyphenols from Enteromorpha clathrata (E. clathrata), commonly found in the southeast coast of China, was achieved using ultrasonic-assisted extraction and multistage extraction followed by one-dimensional coupled with inner-recycling high-speed counter-current chromatography. The structure was identified by mass spectrometry and nuclear magnetic resonance spectra. Seven compounds with a purity of greater than 90% were separated from the ethyl acetate extract of E. clathrata, and identified as hydroquinone, gallic acid, (−)-epigallocatechin, caffeine, (−)-epicatechin, (−)-epigallocatechin-3-O-gallate, and epicatechin-3-O-gallate. These compounds were first separated and identified from E. clathrata. All of the six polyphenols exhibited potent antioxidant activity measured as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, while (−)-epicatechin and epicatechin-3-O-gallate showed poor hydroxyl radical scavenging capacity, in comparison with Vitamin C (VC). The antioxidant activity of polyphenols with the same number of benzene rings was positively proportional to the number of phenolic hydroxyl groups. Esterification appeared to enhance the antioxidant activity of catechin and reduce the hydroxyl radical scavenging capacity of gallic acid. Our results about the separation, identification, and antioxidant activity of polyphenols from E. clathrata provide a basis for further elucidating the relationship between structure and antioxidant activity, which will promote the development and utilization of E. clathrata antioxidants.

Phenolic Composition, Antioxidant Capacity and Antibacterial Activity of White Wormwood (Artemisia herba-alba).

Artemisia herba-alba Asso. (Wormwood) is a wild aromatic herb that is popular for its healing and medicinal effects and has been used in conventional as well as modern medicine. This research aimed at the extraction, identification, and quantification of phenolic compounds in the aerial parts of wormwood using Soxhlet extraction, as well as characterizing their antimicrobial and anitoxidant effects. The phenolic compounds were identified in different extracts by column chromatography, thin layer chromatography (TLC), and high performance liquid chromatography. Five different fractions, two from ethyl acetate extraction and three from ethanolic extraction were obtained and evaluated further. The antimicrobial activity of each fractions was evaluated against two Gram-positive (Bacillus cereus and Staphylococcus aureus) and two Gram-negative microorganisms (Escherichia coli and Proteus vulgaris) using the disc-diffusion assay and direct TLC bioautography assay. Fraction I inhibited B. cereus and P. vulgaris, Fraction II inhibited B. cereus and E. coli, Fraction III inhibited all, except for P. vulgaris, while Fractions IV and V did not exhibit strong antimicrobial effects. Their antioxidant capabilities were also measured by calculating their ability to scavenge the free radical using DPPH method and the ferric reducing antioxidant power (FRAP) assay. Ethanolic fractions III and V demonstrated excellent antioxidant properties with IC50 values less than 15.0 μg/mL, while other fractions also had IC50 values less than 80.0 μg/mL. These antioxidant effects were highly associated with the number of phenolic hydroxyl group on the phenolics they contained. These extracts demonstrated antimicrobial effects, suggesting the different phenolic compounds in these extracts had specific inhibitory effects on the growth of each bacteria. The results of this study suggested that the A. herba-alba can be a source of phenolic compounds with natural antimicrobial and antioxidant properties which can be used for potential pharmaceutical applications.

STRUCTURE-ACTIVITY-RELATIONSHIP OF THE POLYPHENOLS INHIBITION OF α-AMYLASE AND α-GLUCOSIDASE

Background: Diabetes mellitus (DM) is a serious public health challenge, projected by WHO to be one of the 7 leading cause of death by 2030. Medicinal plants have been demonstrated to be useful in DM local management because of polyphenols present in these plants. For an alternative treatment approach especially with polyphenols-rich herbs, knowledge of comparative efficacy of the polyphenols will lead to enhanced therapy especially in postprandial hyperglyceamic control. Materials and Methods: Vegetative parts of Anacardium occidentale, Abelmoschus ecsulentus and Ceiba pentandra, prominent in the local management of DM were identified, collected and subjected to alcoholic extraction. From the crude extracts were isolated agathisflavone, quercetin 3-O-glucoside, quercetin 3-O-diglycoside, mangiferin, isomangiferin and pentagalloyl glucose, belonging to flavonoid, xanthones and tannins structural classes. These polyphenols were evaluated for their potentials to inhibit both α-glucosidase and α-amylase. Physicochemical parameters of the polyphenols were evaluated and molecular docking experiments were carried out to gain insight into the observed inhibitory activity. Results: quercetin 3-O-glucosidewas the most potent of the polyphenols against the two enzymes. Increase in the number of phenolic hydroxyl group did not increase the inhibitory activity and neither computation of the binding energies with the enzymes nor physicochemical parameters of the polyphenols could explain the observed inhibitory activity against the enzymes, across the structural classes. Thus, only the bioassay against the enzymes α-glucosidase and α-amylase correlated well with the use of the plants in treating diabetic mellitus Conclusion: Medicinal plants rich in quercetin 3-O-glycoside may have better treatment outcomes in postprandial hyperglycaemia control.