Structure-bioactivity Relationship Research Articles

Antiviral Chlorinated Drimane Meroterpenoids from the Fungus Talaromyces pinophilus LD-7 and Their Biosynthetic Pathway.

Ten new drimane meroterpenoids talarines A-J (1-10), along with six known analogues (11-16), were isolated from desert soil-derived fungus Talaromyces pinophilus LD-7. Their 2D structures were elucidated by comprehensive interpretation of NMR and HRESIMS data. Electronic circular dichroism calculation was used to establish their absolute configurations. Compounds 2, 10, and 11 showed antiviral activities toward vesicular stomatitis virus with IC50 values of 18, 15, and 23 nM, respectively. The structure-bioactivity relationship indicated that chlorine substitution at C-5 contributed greatly to their antiviral activities. Finally, we identified a new halogenase outside the biosynthetic gene cluster, which was responsible for C-5 halogenation of the precursor isocoumarin 17 as a tailoring step in chlorinated meroterpenoids assembly.

The Horizons of Medical Mineralogy: Structure-Bioactivity Relationship and Biomedical Applications of Halloysite Nanoclay.

Medical mineralogy explores the interactions between natural minerals and living organisms such as cells, tissues, and organs and develops therapeutic and diagnostic applications in drug delivery, medical devices, and healthcare materials. Many minerals (especially clays) have been recognized for pharmacological activities and therapeutic potential. Halloysite clay (Chinese medicine name: Chishizhi), manifested as one-dimensional aluminum silicate nanotubes (halloysite nanotubes, HNTs), has gained applications in hemostasis, wound repair, gastrointestinal diseases, tissue engineering, detection and sensing, cosmetics, and daily chemicals formulations. Various biomedical applications of HNTs are derived from hollow tubular structures, high mechanical strength, good biocompatibility, bioactivity, and unique surface characteristics. This natural nanomaterial is safe, abundantly available, and may be processed with environmentally safe green chemistry methods. This review describes the structure and physicochemical properties of HNTs relative to bioactivity. We discuss surface area, porosity and surface defects, hydrophilicity, heterogeneity and charge of external and internal surfaces, as well as biosafety. The paper provides comprehensive guidance for the development of this tubule nanoclay and its advanced biomedical applications for clinical diagnosis and therapy.

Structure-bioactivity relationship study on anticancer Pd and Pt complexes with aliphatic glycine derivative ligands

To investigate the structure and bioactivity relationship, six Pd(II)/Pt(II) complexes with N-isobutylglycine (L1) and cyclohexylglycine (L2) as N^O amino acid bidentate ligands, 1,10′-phenanthroline (phen) and 2,2′-bipyridine (bipy) as N^N donor ligands, and [Pd(L1)(bipy)]NO3 (1), [Pd(L2)(bipy)]NO3 (2), [Pd(L1)(phen)]NO3 (3), [Pd(L2)(phen)]NO3·2H2O (4), [Pt(L1)(phen)]NO3 (5), along with [Pt(L2)(phen)]NO3 (6) were prepared and then characterized. The geometry of each compound was validated by doing a DFT calculation. Furthermore, tests were conducted on the complexes’ water solubilities and lipophilicity. All bipy complexes had superior aqueous solubility and less lipophilicity in comparison with phen complexes, as well as complexes containing cyclohexyl-glycine compared to isobutyl-glycine complexes, probably because of the steric effects and polarity of cyclohexylglycine. The in-vitro anticancer activities of these compounds were examined against HCT116, A549, and MCF7 cancerous cell lines. Data revealed that all Pd/Pt complexes demonstrate higher anticancer activity than carboplatin, and complexes 3 and 4 are more cytotoxic than cisplatin against the HCT116 cell line, particularly against MCF7 cancerous cells. In addition, among all compounds, complex 4 has more anticancer ability than oxaliplatin. Due to different solubility and lipophilicity behavior, the accumulation of Pt complexes and clinical Pt drugs in each cancerous cell was investigated. The binding capabilities of these complexes to DNA, as the main target in chemotherapy, occur through minor grooves and intercalate into DNA, which was done using absorption, fluorescence, and circular dichroism spectroscopy. Finally, the docking simulation study showed the mode of DNA bindings is in good agreement with the spectral binding data.

Impacts of ultrasound-assisted Fenton degradation and alkaline de-esterification on structural properties and biological effects of pectic polysaccharides from Tartary buckwheat leaves

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn) leaf has abundant rhamnogalacturonan-I enriched pectic polysaccharides, which exert various health-promoting effects. Nevertheless, the potential relationship between the chemical structure and the biological function of pectic polysaccharides from Tartary buckwheat leaves (TBP) remains unclear. Therefore, to bridge the gap between the chemical structure and the biological function of TBP, the impacts of ultrasound-assisted Fenton degradation (UFD) and mild alkaline de-esterification (MAD) on structural properties and biological effects of TBP were systematically studied. Compared with the native TBP (molecular mass, 9.537 × 104 Da), the molecular masses of degraded TBPs (TBP-MMW, 4.811 × 104 Da; TBP-LMW, 2.101 × 104 Da) were significantly reduced by the UFD modification, while their primary chemical structures were overall stable. Besides, compared with the native TBP (esterification degree, 22.73 %), the esterification degrees of de-esterified TBPs (TBP-MDE, 14.27 %; TBP-LDE, 6.59 %) were notably reduced by the MAD modification, while their primary chemical structures were also overall stable. Furthermore, the results revealed that both UFD and MAD modifications could significantly improve the antioxidant, antiglycation, and immunostimulatory effects of TBP. Indeed, TBP’s biological effects were negatively correlated to its molecular mass and esterification degree, while positively linked to its free uronic acids. The findings demonstrate that both UFD and MAD modifications are promising techniques for the structural modification of TBP, which can remarkedly promote its biological effects. Besides, the present results are conducive to better understanding TBP’s structure-bioactivity relationship.

New Antibacterial Peptaibiotics against Plant and Fish Pathogens from the Deep-Sea-Derived Fungus Simplicillium obclavatum EIODSF 020.

Bacterial diseases could severely harm agricultural production. To develop new antibacterial agents, the secondary metabolites of a deep-sea-derived fungus Simplicillium obclavatum EIODSF 020 with antibacterial activities against plant and fish pathogens were investigated by a bioassay-guided approach, which led to the isolation of 11 new peptaibiotics, simplicpeptaibs A-K (1-11). They contain 16-19 residues, including β-alanine, tyrosine, or tyrosine O-sulfate, that were rarely present in peptaibiotics. Their structures were elucidated by spectroscopic analyses (NMR, HRMS, HRMS2, and ECD) and Marfey's method. The primary and secondary structures of novel sulfated peptaibiotic 9 were reconfirmed by single-crystal X-ray diffraction analysis. Genome sequencing of S. obclavatum EIODSF 020 allowed the detection of a gene cluster encoding two individual NRPSs (totally containing 19 modules) that was closely related to simplicpeptaib biosynthesis. Antibacterial investigations of 1-11 together with the previously isolated linear and cyclic peptides from this strain suggested the antibacterial property of this fungus was attributed to the peptaibiotics and cyclic lipopeptides. Among them, compounds 4, 6, 7, and 9 showed significant activity against the tobacco pathogen Ralstonia solanacearum or tilapia pathogens Streptococcus iniae and Streptococcus agalactiae. The antibacterial activity of 6 against R. solanacearum could be enhanced by the addition of 1% NaCl. The structure-bioactivity relationship of simplicpeptaibs was discussed.

Synthesis of quaternary ammonium saltsisonicotinic and nicotinic hydrazones acids and their anti-inflammatory activity

Currently, the number of infections caused by strains of bacteria that are not sensitive to antibiotics and antiseptics is growing worldwide. A similar increase in bacterial resistance is observed for both nosocomial infections and community-acquired human-to-human infections. An important task for chemists and pharmacologists is the synthesis of new compounds and the establishment of a structure-bioactivity relationship. The purpose of this work is to study the effect of the structure of quaternary ammonium derivatives of hydrazones of isonicotinic and nicotinic acids on the manifestation of their anti-inflammatory properties. Results and discussion. The alkylation of nicotinic acid hydrazones produced their new quaternary ammonium salts (43.7-70.7%). The methodology for the synthesis of quaternary ammonium compounds of hydrazones included obtaining a variety of structures by introducing one or two fluorine and bromine-containing fragments into their structure. The structure of compounds was confirmed by 1H, 13C NMR spectroscopy. Conclusion. New quaternary ammonium salts of nicotinic acid hydrazones have been obtained. The study of anti-inflammatory activity was carried out using the method of formalin paw edema in rats. The acute inflammatory reaction was reproduced by subplantar administration of 2% formalin solution. Compared with ibuprofen at a dosage of 100 mg/kg, these compounds were ineffective (p2<0.05). According to the results of the analysis of possible pharmacological effects, it was also revealed that new compounds may have an effect on the regulation and production of ketone bodies, the enzymatic activity of transaminases. New alkylated hydrazones of isonicotinic and nicotinic acids may be of interest for studying their antituberculous and antiviral activities.

Microascones, Decahydrofluorene-Class Alkaloids from the Marine-Derived Fungus Microascus sp. SCSIO 41821.

Eight new decahydrofluorene-class alkaloids, microascones A and B (1 and 2), 2,3-epoxyphomapyrrolidone C (3), 14,16-epiascomylactam B (4), 24-hydroxyphomapyrrolidone A (5), and microascones C-E (6-8), along with five known analogs (9-13) were isolated from the marine-derived fungus Microascus sp. SCSIO 41821. Compounds 1 and 2 have an unprecedented complex macrocyclic alkaloid skeleton with a 6/5/6/5/6/5/13 polycyclic system. Their structures and absolute configurations were determined by spectroscopic analysis, quantum chemical calculations of ECD spectra, and 13C NMR chemical shifts. Compounds 10-13 showed selective enzyme inhibitory activity against PTPSig, PTP1B, and CDC25B, and 4, 9, and 10 exhibited strong antibacterial activity against seven tested pathogens. Their structure-bioactivity relationship was discussed, and a plausible biosynthetic pathway for 1-8 was also proposed.

Evaluation of Bioactive Effects of Five Plant Extracts with Different Phenolic Compositions against Different Therapeutic Targets.

Plant extracts rich in phenolic compounds have been reported to exert different bioactive properties. Despite the fact that there are plant extracts with completely different phenolic compositions, many of them have been reported to have similar beneficial properties. Thus, the structure-bioactivity relationship mechanisms are not yet known in detail for specific classes of phenolic compounds. In this context, this work aims to demonstrate the relationship of extracts with different phenolic compositions versus different bioactive targets. For this purpose, five plant matrices (Theobroma cacao, Hibiscus sabdariffa, Silybum marianum, Lippia citriodora, and Olea europaea) were selected to cover different phenolic compositions, which were confirmed by the phytochemical characterization analysis performed by HPLC-ESI-qTOF-MS. The bioactive targets evaluated were the antioxidant potential, the free radical scavenging potential, and the inhibitory capacity of different enzymes involved in inflammatory processes, skin aging, and neuroprotection. The results showed that despite the different phenolic compositions of the five matrices, they all showed a bioactive positive effect in most of the evaluated assays. In particular, matrices with very different phenolic contents, such as T. cacao and S. marianum, exerted a similar inhibitory power in enzymes involved in inflammatory processes and skin aging. It should also be noted that H. sabdariffa and T. cacao extracts had a low phenolic content but nevertheless stood out for their bioactive antioxidant and anti-radical capacity. Hence, this research highlights the shared bioactive properties among phenolic compounds found in diverse matrices. The abundance of different phenolic compound families highlights their elevated bioactivity against diverse biological targets.

Advancing Bioactivity Prediction through Molecular Docking and Self-Attention.

Bioactivity refers to the ability of a substance to induce biological effects within living systems, often describing the influence of molecules, drugs, or chemicals on organisms. In drug discovery, predicting bioactivity streamlines early-stage candidate screening by swiftly identifying potential active molecules. The popular deep learning methods in bioactivity prediction primarily model the ligand structure-bioactivity relationship under the premise of Quantitative Structure-Activity Relationship (QSAR). However, bioactivity is determined by multiple factors, including not only the ligand structure but also drug-target interactions, signaling pathways, reaction environments, pharmacokinetic properties, and species differences. Our study first integrates drug-target interactions into bioactivity prediction using protein-ligand complex data from molecular docking. We devise a Drug-Target Interaction Graph Neural Network (DTIGN), infusing interatomic forces into intermolecular graphs. DTIGN employs multi-head self-attention to identify native-like binding pockets and poses within molecular docking results. To validate the fidelity of the self-attention mechanism, we gather ground truth data from crystal structure databases. Subsequently, we employ these limited native structures to refine bioactivity prediction via semi-supervised learning. For this study, we establish a unique benchmark dataset for evaluating bioactivity prediction models in the context of protein-ligand complexes, showcasing the superior performance of our method (with an average improvement of 27.03%) through comparison with 9 leading deep learning-based bioactivity prediction methods.

Green-Chemical Strategies for Production of Tailor-Made Chitooligosaccharides with Enhanced Biological Activities.

Chitooligosaccharides (COSs) are b-1,4-linked homo-oligosaccharides of N-acetylglucosamine (GlcNAc) or glucosamine (GlcN), and also include hetero-oligosaccharides composed of GlcNAc and GlcN. These sugars are of practical importance because of their various biological activities, such as antimicrobial, anti-inflammatory, antioxidant and antitumor activities, as well as triggering the innate immunity in plants. The reported data on bioactivities of COSs used to contain some uncertainties or contradictions, because the experiments were conducted with poorly characterized COS mixtures. Recently, COSs have been satisfactorily characterized with respect to their structures, especially the degree of polymerization (DP) and degree of N-acetylation (DA); thus, the structure-bioactivity relationship of COSs has become more unambiguous. To date, various green-chemical strategies involving enzymatic synthesis of COSs with designed sequences and desired biological activities have been developed. The enzymatic strategies could involve transglycosylation or glycosynthase reactions using reducing end-activated sugars as the donor substrates and chitinase/chitosanase and their mutants as the biocatalysts. Site-specific chitin deacetylases were also proposed to be applicable for this purpose. Furthermore, to improve the yields of the COS products, metabolic engineering techniques could be applied. The above-mentioned approaches will provide the opportunity to produce tailor-made COSs, leading to the enhanced utilization of chitin biomass.

Degradation products of aflatoxin M1 (AFM1) formed by high voltage atmospheric cold plasma (HVACP) treatment

Cold plasma technology is a novel non-thermal technology that has shown promising results for food decontamination and improving food safety. This study is a continuation of a previous investigation of the treatment of AFM1-contaminated skim and whole milk samples by HVACP. Previous research has shown HVACP is effective in degrading aflatoxin M1 (AFM1) in milk. The goal of this study is to identify the degradation products of AFM1 after HVACP treatment in pure water. An HVACP direct treatment at 90 kV using modified air (MA65: 65% O2, 30% CO2, 5% N2) was performed for up to 5 min at room temperature on a 5.0 mL water sample in a Petri dish artificially contaminated with 2 μg/mL of AFM1. The degradants of AFM1 were analyzed and their molecular formulae were elucidated by using high-performance liquid-chromatography time-of-flight mass spectrometry (HPLC−TOF-MS). Three main degradation products were observed and based on mass spectrometric fragmentation pathways, chemical structures for the degradation products were tentatively assigned. According to the structure–bioactivity relationship of AFM1, the bioactivity of the AFM1 samples treated with HVACP was reduced due to the disappearance of the C8–C9 double bond in the furofuran ring in all of the degradation products.

De Novo-designed antimicrobial peptides with broad-spectrum antimicrobial potency and rapid wound disinfection

Antimicrobial peptides (AMPs) are widely regarded as a promising antibiotic alternative to current antibiotics in combating bacterial resistance. Cost-effective AMPs with outstanding antibacterial activity, fast killing kinetics, good biocompatibility, and strong stability are in urgent need. In this work, we took the short AMP G(IIKK)3I (denoted as G3-COOH, a de novo AMP) as template and mediated its physicochemical parameters by altering its hydrophobic and hydrophilic amino acid type, composition, amino acid sequence, and amino acid configuration to optimize its antibacterial performance and clarify the structure-bioactivity relationship. The results showed that AMPs with stronger hydrophobicity imposed stronger antibacterial activities, more rapid killing kinetics, but greater cytotoxicity and hemolytic activity as well. Among all the designed AMPs, Trp-substituting variants GW1 (G(WIKK)3W) and GW2 (G(IWKK)3W) showed the strongest antibacterial activity, good selectivity, and good salt and serum resistance. Particularly, GW1 presented very rapid bactericidal kinetics, which achieved 99.9% bacterial killing of all the tested strains in 0.25 min. Antibacterial mechanism investigations suggested that they destroyed membrane structure and eventually killed the bacteria. Furthermore, changing their chirality from L- to D-configuration (D-GW1 and D-GW2) had no obvious effects on their antibacterial activity, bactericidal kinetics, cytotoxicity, and hemolytic activity, but improved their biostability in serum. Subsequently, the excellent in vivo antibacterial performance of D-GW1 and its ability to effectively promote wound healing and re-epithelialization were confirmed in S. aureus-infected rat model. This work offers valuable insights into the structure-property-bioactivity relationship of AMPs and promote the development of AMP-based therapeutics.

Structure-Bioactivity Relationship of the Functionalized Polysulfone with Triethylphosphonium Pendant Groups: Perspective for Biomedical Applications.

Development of new biomaterials based on polysulfones tailored to act in various biomedical fields represents a promising strategy which provides an opportunity for enhancing the diagnosis, prevention, and treatment of specific illnesses. To meet these requirements, structural modification of the polysulfones is essential. In this context, for design of new materials with long-term stability, enhanced workability, compatibility with biological materials and good antimicrobial activity, the functionalization of chloromethylated polysulfones with triethylphosphonium pendant groups (PSFEtP+) was adopted. The surface chemistry analysis (Fourier transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX)), rheological properties, morphological aspects (Scanning electron microscopy (SEM), polarized light microscopy (POM)), and antimicrobial activity of the synthetized polysulfone were investigated to establish the relationship between its structure and properties, as an important indicator for targeted applications. Based on the obtained features, evaluated by the relationship between the rheological properties and microstructural aspects, and also the response at the biomaterial-bacteria interface, these qualities have been confirmed in their performance, in terms of thermal stability, antimicrobial activity, and also an increase in lifetime. Consequently, derived results constitute the preliminary basis for future tests concerning their functionality as gel matrices in biomedical devices.

Secondary Metabolites from Marine-Derived Bacteria with Antibiotic and Antibiofilm Activities against Drug-Resistant Pathogens.

The search for new antibiotics against drug-resistant microbes has been expanded to marine bacteria. Marine bacteria have been proven to be a prolific source of a myriad of novel compounds with potential biological activities. Therefore, this review highlights novel and bioactive compounds from marine bacteria reported during the period of January 2016 to December 2021. Published articles containing novel marine bacterial secondary metabolites that are active against drug-resistant pathogens were collected. Previously described compounds (prior to January 2016) are not included in this review. Unreported compounds during this period that exhibited activity against pathogenic microbes were discussed and compared in order to find the cue of the structure-bioactivity relationship. The results showed that Streptomyces are the most studied bacteria with undescribed bioactive compounds, followed by other genera in the Actinobacteria. We have categorized the structures of the compounds in the present review into four groups, based on their biosynthetic origins, as polyketide derivatives, amino acid derivatives, terpenoids, as well as compounds with mixed origin. These compounds were active against one or more drug-resistant pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), vancomycin-resistant Enterococci (VRE), multidrug-resistant Mycobacterium tuberculosis (MDR-TB), and amphotericin B-resistant Candida albicans. In addition, some of the compounds also showed activity against biofilm formation of the test bacteria. Some previously undescribed compounds, isolated from marine-derived bacteria during this period, could have a good potential as lead compounds for the development of drug candidates to overcome multidrug-resistant pathogens.

Phyto-Mediated Controllable Synthesis of ZnO Clusters with Bactericidal Activity.

The rapid development of antibiotic resistance has been considered a major threat to public health. Nanomaterials have risen to be an effective weapon to tackle this problem through multiple antibacterial mechanisms. The improved and tailored physiochemical properties of fine-tuned secondary nanoarchitectures contribute to the superior bactericidal actions of metal oxide structures. However, it is still challenging to construct secondary structures through mild green manufacturing methods. Here, we report the preferred antibacterial ZnO nanocrystal clusters formed by a green structure-tuning synthesis process, in which the primary ZnO nanoparticles with sizes <10 nm were assembled into different forms of clusters depending on the zinc salt concentration and temperature. ZnO clusters with a stable loose-assembly structure and a rougher surface exhibited better bactericidal ability with minimal inhibitory concentrations of 0.5 and 0.1 mg/mL against Escherichia coli and Staphylococcus aureus, respectively. The underlying mechanism is related to enhancing contact with bacteria, releasing small ZnO nanoparticles, and generating additional reactive oxygen species, which could aggravate the damage to bacterial cell membrane and eventually lead to bacterial death. Furthermore, attachment of phenolic compounds from olive leaf extract would promote membrane penetration by ZnO nanoparticles, resulting in the improvement of antibacterial activities, which profit from the green route mediated by Olea europaea leaf extract that could structure-tune ZnO nanocrystal clusters in one simple step that retains the active ingredients on the nanoparticles. This work proposes a feasible and clean strategy to improve the structure-bioactivity relationship of ZnO by controlling its growth into a preferable structure, and the developed ZnO clusters have a good prospect in antibacterial applications because of their excellent performance and green fabrication method.

Five new verrucosidin derivatives from Penicillium polonicum, a deep-sea cold-seep sediment isolated fungus

Five new verrucosidin derivatives, poloncosidins G–K (1–5), were isolated from the deep sea cold-seep sediment-derived fungus Penicillium polonicum CS-252. Their planar structures were elucidated by discreet analysis of the NMR spectroscopic and HRESIMS spectrometric data. The absolute configurations of compounds 1–5 were deduced from the combination of the modified Mosher's method and quantum chemical calculations of their ECD and NMR (with DP4+ probability analysis) data. The antimicrobial activities against several human- and aquatic-pathogenic bacteria of all the isolated compounds were evaluated and the structure-bioactivity relationship was briefly discussed.

Asymmetrical flow field-flow fractionation combined with ultrafiltration: A novel and high-efficiency approach for separation, purification, and characterization of Ganoderma lucidum polysaccharides

Ganoderma lucidum polysaccharide (GLP) has attracted increasing attention owing to its multiple pharmacological effects. However, the establishment of a structure-bioactivity relationship is possible only if highly purified and accurately characterized GLP is used. In this study, a combined technique based on asymmetrical flow field-flow fractionation (AF4), ultrafiltration, and the Sevag method was developed to improve the purification process of GLP. Deionized water was used throughout this study which avoids the dialysis desalting process. Furthermore, the molecular weight (Mw) and radius of gyration (Rg) of the purified GLP were characterized by AF4 coupled online ultraviolet–visible (UV), multiangle light scattering (MALS), and differential refractive index (dRI) detectors (AF4-UV-MALS-dRI). The results demonstrated that after removal of the larger size proteins, one highly purified GLP fraction (polysaccharide content of 108.37 ± 0.45%) and its structural information (i.e., Mw, Rg, and apparent density) were obtained in a single run owing to a combination of mechanisms of ultrafiltration and AF4 separation. The results suggested that the method developed in this study for separation, purification, and characterization of GLP is highly efficient, which could help to better understand its structure-function relationships.

Effects of various degrees of esterification on antioxidant and immunostimulatory activities of okra pectic-polysaccharides.

Pectic-polysaccharides are considered as one of the most abundant bioactive components in okra, which possess various promising health-promoting effects. However, the knowledge regarding the structure-bioactivity relationship of okra pectic-polysaccharides (OPP) is still limited. In this study, effects of various degrees of esterification (DEs) on in vitro antioxidant and immunostimulatory activities of OPP were analyzed. Results displayed that OPP with high (42.13%), middle (25.88%), and low (4.77%) DE values were successfully prepared by mild alkaline de-esterification, and their primary chemical structures (compositional monosaccharide and glycosidic linkage) and molecular characteristics (molecular weight distribution, particle size, and rheological property) were overall stable. Additionally, results showed that the notable decrease of DE value did not significantly affect antioxidant activities [2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and nitric oxide (NO) radical scavenging abilities as well as ferric reducing antioxidant power (FRAP)] of OPP, suggesting that the DE was not closely related to its antioxidant activity. In fact, the slight decrease of antioxidant activity of OPP after the alkaline de-esterification might be attributed to the slight decrease of uronic acid content. Nevertheless, the immunostimulatory effect of OPP was closely related to its DE, and a suitable degree of acetylation was beneficial to its in vitro immunostimulatory effect. Besides, the complete de-acetylation resulted in a remarkable reduction of immune response. The findings are beneficial to better understanding the effect of DE value on antioxidant and immunomodulatory activities of OPP, which also provide theoretical foundations for developing OPP as functional foods or health products.

Structural Characterization of a Low Molecular Weight HG-Type Pectin From Gougunao Green Tea.

Tea is a popular beverage with a long history of safe and healthy use. Tea polysaccharide is a bioactive component extracted from tea, which has attracted more and more attention in recent decades. In this article, an acidic polysaccharide Gougunao tea polysaccharide (GPS) was isolated from Gougunao green tea by hot water extraction and ethanol precipitation. After purification by a diethylaminoethyl (DEAE) Sepharose Fast Flow column and a Sephacryl S-400 column, several homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) fractions were obtained. Fraction GPS2b with the highest yield was selected for structural characterization by methylation and nuclear magnetic resonance (NMR) analysis. GPS2b was found to be an HG-type pectic polysaccharide (degree of methyl esterification [DE], 51.6%) with low molecular weight (Mw, 36.8 kDa). It was mainly composed of →4)-α-GalpA- (1→ and →4)-α-GalpA-6-OMe-(1→. In addition, a minor highly branched RG-I domain was identified in this fraction. The investigation of structural features of tea polysaccharides can provide insights to understand their structure-bioactivity relationship.

Green Synthesis of Robust Selenium Nanoparticles via Polysaccharide–Polyphenol Interaction: Design Principles and Structure–Bioactivity Relationship

Selenium is an essential micronutrient and is well known for its role in regulating metabolism. However, it is also highly toxic in some of its forms and above certain concentration levels. Amorphous selenium nanoparticles (SeNPs) are extremely unstable and convert into non-bioactive or gray elemental selenium with crystal-type structures due to aggregation, which limits its antioxidant and anti-tumor activities. To overcome these limitations, monodisperse SeNPs were obtained by stabilizing SeNPs with glucan and rosmarinic acid (RA) via Se–O bonds and polysaccharide–polyphenol interactions. The prepared glucan-RA-SeNPs were found much more stable than both SeNPs and glucan-stabilized SeNPs. Meanwhile, glucan-RA-SeNPs displayed enhanced bioactivities including an improved free radical scavenging ability and an increased cytotoxicity toward cancer cells. The underlying mechanism might be related to caspase activation by glucan-RA-SeNPs, thus overproducing intracellular reactive oxygen species and eventually resulting in cancer cell apoptosis. Our work proposes a feasible strategy for improving the structure–bioactivity of SeNPs through polysaccharide–polyphenol interaction.