Metal Ion Chelating Research Articles

Hg (II) and Cd (II) Heavy Metal Ions Detection Based On Fluorescence Using Zn (II) Metal Ion Complex with Pyrazoline Derivatives Ligand

Pyrazoline derivatives can be used as ligands because they have photophysical properties and can chelate metal ions which cause very strong absorption, emission and have a fluorescence properties. Therefore, in recent years, pyrazoline ligands and their derivatives have been widely used for chemosensors. This research aims to detect fluorescence-based heavy metal ions Hg2+ and Cd2+ using a metal ion complex compound Zn2+ with pyrazoline derivative ligand. The research was started by synthesizing pyrazoline-derived ligands, then synthesizing complex compounds. Complex compounds were characterized using Fourier Transform Infra Red (FTIR), UV-Vis Spectrophotometer, and Spectrofluorometer. Then, a fluorescence study was carried out to determine the type of fluorosensor for complex compounds with the addition of heavy metal ions Cd2+ and Hg2+. The last stage is UV-Vis spectroscopy study on the addition of heavy metal ions Hg2+ and Cd2+. Pyrazoline derivative ligand obtained as para-di-2-(1-phenyl-3-pyridyl-4,5-dihydro-1H-pyrazole-5-yl)benzene is a yellow solid. The metal ion complex compound Zn2+ with pyrazolin derivative ligand is a brown colored compound, has a yield of 45 % and a melting point is 245 oC. The FTIR spectrum showed the presence of functional groups such as amine, C-H aromatic, C=N, C=C aromatic, C-N, Zn-N and Zn-Cl. Analysis with UV-Vis spectrophotometer showed that there was a shift in the maximum wavelength from the ligand to the Zn(II)-ligand complex, namely 240 nm to 246 nm and 363 nm with molar absorptivity values (log ) of 4.56 and 4.28, respectively. For fluorescence analysis, two absorbance peaks were obtained, namely at a wavelength of 370 nm with an intensity of 3644 a.u and 478 m at 8216 a.u. The results of fluorescence chemosensor studies on the addition of heavy metal ions Hg2+ and Cd2+ showed that the metal ion complex compound Zn2+ with pyrazoline-derived ligands can detect heavy metal ions Hg2+ and Cd2+ with a turn-on type.

Biological Functions of Antioxidant Dipeptides.

In the history of modern nutritional science, understanding antioxidants is one of the major topics. In many cases, food-derived antioxidants have π conjugate or thiol group in their molecular structures because π conjugate stabilizes radical by its delocalization and two thiol groups form a disulfide bond in its antioxidative process. In recent years, antioxidant peptides have received much attention because for their ability to scavenge free radicals, inhibition of lipid peroxidation, chelation of transition metal ions, as well as their additional nutritional value. Among them, dipeptides are attracting much interest as post-amino acids, which have residues in common with amino acids, but also have different physiological properties and functions from those of amino acids. Especially, dipeptides containing moieties of several amino acid (tryptophan, tyrosine, histidine, cysteine, and methionine) possess potent antioxidant activity. This review summarizes previous details of structural property, radical scavenging activity, and biological activity of antioxidant dipeptide. Hopefully, this review will help provide a new insight into the study of the biological functions of antioxidant dipeptides.

Preparation and characterization of lipophilic antioxidative peptides derived from mung bean protein

This study aimed to prepare and characterize antioxidative hydrolysate and its lipophilic peptides derived from mung bean protein. Our results indicated that the hydrolysate prepared with 120 min hydrolysis (MPH) possessed superb DPPH, ABTS radical scavenging activity and metal ion-chelating activity with IC50 values of 11.19 ± 0.02, 18.06 ± 0.18 and 3.78 ± 0.59 µg/mL, respectively. MPH could also effectively retard lipid oxidation for oil-in-water emulsion (up to 50%) and linoleic acid (up to 94%), as well as for bulk oil. Interestingly, the lipophilic peptide fraction (MPHP) extracted from MPH could suppress the formation of primary (up to 50%) and secondary oxidation products (up to 90%) in bulk oil. Ten lipophilic peptides identified from MPHP using LC-MS/MS possessed high amounts of hydrophobic amino acids and histidine, which might favor peptides interacting and/or forming hydrogen bonds with lipid radicals. These findings provide a new perspective for lipophilic peptides in fortifying lipids as natural antioxidants.

Polysaccharides From Pogostemon cablin (Blanco) Benth.: Characterization and Antioxidant Activities.

Two polysaccharide fractions from Pogostemon cablin (Blanco) Benth. (P. cablin) (designated as PCB-1 and PCB2-1) were isolated by water extraction and purified by Sepharose chromatography. The chemical properties of the polysaccharides were characterised, and their antioxidant activities were evaluated. The sugar content of the crude polysaccharide (PCB), PCB-1, and PCB2-1 was 58.74, 90.23 and 88.61%, respectively. The molecular weights of PCB-1 and PCB2-1 were determined to be 97.8 and 12.8 kDa, respectively. Monosaccharide composition analysis showed that all the three polysaccharides consisted of mannose, rhamnose, galacturonic acid, galactose, glucose, and arabinose, but with varying molar ratios. The polysaccharides exhibited significantly high antioxidant activities in vitro based on the scavenging activity against hydroxyl radicals, metal ion-chelating and ferric-reducing abilities. In vivo experiments in an oxidatively damaged mice model showed that PCB-1 increased the levels of antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase, and inhibited malondialdehyde formation in the serum and liver. These findings suggest that PCB-1 has significant potential as an antioxidant in functional foods.

Sources and Chemistry of Flavonoids; their Biological and Therapeutic Potential

Flavonoids are natural polyphenolic compounds, which are responsible for the taste and colors of medicinal plants, herbs, fruits, vegetables. Fruits (e.g., Berries, cherries, plums, apples, lemons, oranges, and grapes etc) and vegetables (e.g., broad beans, olives, onions, spinach, shallot etc) are the main sources of flavonoids. They also exist abundantly in cocoa products, black and green tea, red wine, red pepper, chamomile, celery, parsley, ginkgo, and mint. Flavonoids derivatives can also be synthesized through esterification, halogenation, alkoxylation, alkylation, aromatic hydroxylation, acylation and conjugation with various organic compounds. Flavonoids can be supplemented in a staple of food as nutraceutical agents and have an important role in human diet. They possess diverse biological activities including anti-inflammation, anti-oxidation, anti-cancer, anti-diabetes, anti-obesity, antimutagenic, neuroprotective and also have beneficial effects on oxidative stress, inflammation, insulin resistance, lipid metabolism and neurodegenerative diseases (e.g., amyotrophic lateral sclerosis, Huntington’s disease, Parkinson’s disease and Alzheimer’s disease). Flavonoids contain a 15-carbon skeleton; the basic structure consists of a flavan nucleus, a combination of two benzene and one pyran rings. Flavonoids are divided into eight important groups i.e., flavones, flavanols, isoflavones, flavan-3-ols, flavanonols, anthocyanidins, chalcones, and flavanones. A structure-activity relationship exists between flavonoids and their antioxidant activities. Flavonoids are effective in chelating metal ions and scavenging free radicals. The antioxidant properties of flavonoids are governed by their –OH groups, differences in hydrophobicity and molecular planarity.

Multifunctional Gel Films of Marine Polysaccharides Cross-Linked with Poly-Metal Ions for Wound Healing.

The development of an efficient and convenient material to improve skin tissue regeneration is a major challenge in healthcare. Inspired by the theory of moist wound healing, portable chitooligosaccharide (COS)/sodium alginate (SA) dual-net gel films containing multiple metal ions were prepared by a casting and in-situ spray method, which can be used to significantly promote wound healing without the use of therapeutic drugs. A variety of divalent cations was introduced in this experiment to improve the advantages of each metal ion by forming metal ion chelates with COS. Moreover, the physicochemical properties and antioxidant properties of nIon2+-COS/SA gel films were systematically characterized and evaluated by in vitro experiments. The gel films showed good antibacterial activity against Gram-negative and Gram-positive bacteria. In addition, the gel films showed good cytocompatibility in cellular experiments, and the gel films with Zn2+ and Sr2+ addition significantly accelerated wound healing in whole skin defect model experiments. Therefore, this nIon2+-COS/SA gel film is an ideal candidate material for wound dressing.

The interplay between selective etching induced cation defects and active oxygen species for volatile organic compounds degradation

Surface electronic structure of transition metal oxides plays a vital role in determining the catalytic performance. Herein, we present a selective etching strategy to tune the surface cation defect of the CuWO4 (CW) catalyst for improving the catalytic activity of volatile organic compounds (VOCs). HRTEM, SEM-EDS, EPR, and XPS show that the chelation of metal ions in acetic acid and ammonium hydroxide can help to remove a small number of surface cations in CW to form suitable W defects. Cu L-edge and O K-edge XAS, Raman, and O 1s XPS spectrum illustrate that cation defects can improve the hybrid orbits of metal-oxygen bonds, which increases the activity of surface lattice oxygen and metal sites. In-situ DRIFTS spectra reveal that CW with cation defects can easily adsorb toluene, cleave and oxidize benzene ring, and desorb CO2 because of more surface dangling bonds and active oxygen species. Therefore, the toluene conversion rates of CW-Aci and CW-Alk are much higher than CW in VOCs degradation and the catalytic performance improved 33 times and 22 times at 200 °C, respectively. This study offers a new pathway in engineering surface electronic structure and highlights the interplay between cation defects and active oxygen species.

Recent advances of chitosan-based polymers in biomedical applications and environmental protection

Interest in polymer-based biomaterials such as chitosan and its modifications and also the methods of their application in various fields of science is uninterruptedly growing. Owing to unique physicochemical, biological, ecological, physiological properties, such as biocompatibility, biodegradability, stability in the natural environment, non-toxicity, high biological activity, economic affordability, chelating of metal ions, high sorption properties, chitosan is used in various biomedical and industrial processes. The reactivity of the amino and hydroxyl groups in the structure makes it more interesting for diverse applications in drug delivery, tissue engineering, wound healing, regenerative medicine, blood anticoagulation and bone, tendon or blood vessel engineering, dentistry, biotechnology, biosensing, cosmetics, water treatment, agriculture. Taking into account the current situation in the world with COVID-19 and other viruses, chitosan is also active in the form of a vaccine system, it can deliver antibodies to the nasal mucosa and load gene drugs that prevent or disrupt the replication of viral DNA/RNA, and deliver them to infected cells. The presented article is an overview of the nowaday state of the application of chitosan, based on literature of recent years, showing importance of fundamental and applied studies aimed to expand application of chitosan-based polymers in many fields of science.

Pharmacokinetics and tissue distribution of orally administrated imidazole dipeptides in carnosine synthase gene knockout mice.

Imidazole dipeptides (ID) are abundant in skeletal muscle and the brain and have various functions, such as antioxidant, pH-buffering, metal-ion chelation. However, the physiological significance of ID has not been fully elucidated. In this study, we orally administered ID to conventional carnosine synthase gene-deficient mice (Carns-KO mice) to investigate the pharmacokinetics. Carnosine or anserine was administered at a dose of 500 mg (∼2 mmol) per kilogram of mouse body weight, and ID contents in the tissues were measured. No ID were detected in untreated Carns-KO mice. In the ID treatment groups, the ID concentrations in the tissues increased in a time-dependent manner in the gastrocnemius muscle, soleus muscle, and cerebrum after ID administration. Our findings suggest that the Carns-KO mice are a valuable animal model for directly evaluating the effects of dietary ID and for elucidating the physiological functions of oral ID administration.

Discovery of Novel 3-Hydroxyquinazoline-2,4(1H,3H)-Dione Derivatives: A Series of Metal Ion Chelators with Potent Anti-HCV Activities.

Millions of people worldwide suffer from acute or chronic liver inflammation caused by the hepatitis C virus (HCV). Metal ion chelators have achieved widespread success in the development of antiviral drugs. Some inhibitors with metal ion chelating structures have been proven to have good inhibitory activities on non-structural protein 5B (NS5B) polymerase. However, most of the reported metal ion chelators showed poor anti-HCV potency at the cellular level. Hence, we designed and synthesized a series of 3-hydroxyquinazoline-2,4(1H,3H)-dione derivatives with novel metal ion chelating structures. Typical compounds such as 21h, 21k, and 21t showed better anti-HCV activities than ribavirin with EC50 values less than 10 μM. 21t is currently known as one of the metal ion chelators with the best anti-HCV potency (EC50 = 2.0 μM) at the cellular level and has a better therapeutic index (TI > 25) as compared to ribavirin and the reported compound 6. In the thermal shift assay, the representative compounds 21e and 21k increased the melting temperature (Tm) of NS5B protein solution by 1.6 °C and 2.1 °C, respectively, at the test concentration, indicating that these compounds may exert an anti-HCV effect by targeting NS5B. This speculation was also supported by our molecular docking studies and ultraviolet-visible (UV-Vis) spectrophotometry assay, in which the possibility of binding of 3-hydroxyquinazoline-2,4(1H,3H)-diones with Mg2+ in the NS5B catalytic center was observed.

Pharmacological potential of serially extracted Solanum xanthocarpum fruit extracts and their phytochemical characterization

ABSTRACT Pharmacological potential of serially extracted Solanum xanthocarpum fruit (SXF) extracts in terms of antioxidant, anticancer, and antibacterial activities was evaluated. Chemical characterization of the potent extract was done by HPLC, LC-MS-MS, and GC-MS techniques. In vitro antioxidant models, viz. hydroxyl radical scavenging, metal ion chelation, total antioxidant capacity, and ferric reducing antioxidant power, were used to assess the antioxidant potential of extract. Cytotoxicity of the SXF extracts was tested against prostate, ovary, and breast cancer cell lines (DU-145, IGR-OV-1, and MCF-7) using sulforhodamine (SRB) assay. The antibacterial potential was assessed against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella pneumonia, and Escherichia coli bacteria. Results indicated potential pharmacological activities and the presence of pharmacologically active phytoconstituents in the SKF extracts.

Achieving High-Performance Molecular Rectification through Fast Screening Alkanethiol Carboxylate-Metal Complexes Electroactive Units

Achieving High-Performance Molecular Rectification through Fast Screening Alkanethiol Carboxylate-Metal Complexes Electroactive Units

Evaluation of Zn2+- and Cu2+-Binding Affinities of Native Cu,Zn-SOD1 and Its G93A Mutant by LC-ICP MS.

The tight binding of Cu and Zn ions to superoxide dismutase 1 (SOD1) maintains the protein stability, associated with amyotrophic lateral sclerosis (ALS). Yet, the quantitative studies remain to be explored for the metal-binding affinity of wild-type SOD1 and its mutants. We have investigated the demetallation of Cu,Zn-SOD1 and its ALS-related G93A mutant in the presence of different standard metal ion chelators at varying temperatures by using an LC-ICP MS-based approach and fast size-exclusion chromatography. Our results showed that from the slow first-order kinetics both metal ions Zn2+ and Cu2+ were released simultaneously from the protein at elevated temperatures. The rate of the release depends on the concentration of chelating ligands but is almost independent of their metal-binding affinities. Similar studies with the G93A mutant of Cu,Zn-SOD1 revealed slightly faster metal-release. The demetallation of Cu,Zn-SOD1 comes always to completion, which hindered the calculation of the KD values. From the Arrhenius plots of the demetallation in the absence of chelators ΔH‡ = 173 kJ/mol for wt and 191 kJ/mol for G93A mutant Cu,Zn-SOD1 was estimated. Obtained high ΔH values are indicative of the occurrence of protein conformational changes before demetallation and we concluded that Cu,Zn-SOD1 complex is in native conditions kinetically inert. The fibrillization of both forms of SOD1 was similar.

Chemical stability of proton exchange membranes synergistically promoted by organic antioxidant and inorganic radical scavengers

The synergistic effects between organic antioxidants with metal ion chelation ability and inorganic radical scavengers were investigated. The different perfluorosulfonic acid (PFSA) composite membranes were prepared by single doping and codoping of alizarin (AZR) and cerium ions. AZR and cerium ion codoping not only significantly enhanced the oxidative stability of the membrane but also lessened both the migration of cerium ions from the membrane and the ionic cross-linkages of cerium ions with sulfonic acid groups. AZR/Ce codoping of the PFSA composite membrane exhibited a maximum power density of 966 mW cm−2 at 75 °C under 80% RH, which was 89.45% of that of the pristine PFSA membrane, whereas only 79.37% remained for cerium ion single doping of the membrane under the same conditions. The AZR/Ce-codoped PFSA composite membrane released much less fluoride than the single-doped PFSA, AZR, or cerium ion composite membranes. The antioxidation effects of AZR/Ce codoping of the PFSA composite membrane were also studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical hydrogen crossover analysis, and cell performance analysis. Notably, the open-circuit voltage (OCV) test indicated that the AZR/Ce-codoped PFSA composite membrane was still viable after 456 h of testing, whereas the other membranes were seriously damaged.

Supplementation of Biscuit with Moringa Oleifera Seed Protein Enhanced Its in-vitro Antioxidative, Antidiabetic and anti-inflammatory Properties

ABSTRACT Biscuit was supplemented with Moringa oleifera seed protein concentrate at 2, 4 and 6%. Compared to the control sample (100% wheat biscuit), supplementation resulted in improved antioxidative properties – DPPH (40–51%) against 31% (control), hydroxyl radical (45–70%) against 30% (control), metal ion chelation (42–54%) against 40% (control), ABTS (0.009–0.013 mmol/g against 0.007 mmol/g (control) but reduced FRAP (2.81–6.68 mg/g) against 8.2 mg/g (control). The in vitro antidiabetic properties showed that the supplemented biscuit had a range of 39 to 57% inhibition against α-glucosidase against 30% (control) and 1.81 to 24.25% inhibition against α-amylase against (1.65%). Supplementation with mspc also showed better potential to inhibit lipid peroxidation. Anti-inflammatory properties evaluated through the inhibition of albumin denaturation and anti-hemolytic assays showed that enrichment with mspc is safe. It was concluded that supplementing biscuit with mspc is safe and may provide enhanced antioxidative, anti-inflammatory as well as inhibition against α-amylase and α-glucosidase.

Non-clinical studies indicating lack of interactions between iron/calcium ions and linzagolix, an orally available GnRH antagonist

Linzagolix is an orally available gonadotropin-releasing hormone antagonist used to treat sex-hormone-dependent diseases in women. This study aimed to investigate drug-drug interactions between linzagolix and iron/calcium ions in the intended clinical setting by conducting pharmacokinetic studies in vitro and in rats. Insoluble precipitate formation with metal ions was evaluated by measuring linzagolix concentrations in four types of bio-relevant dissolution media (fasted/fed state simulated gastric fluid and fasted/fed state simulated gastric fluid version 2), and chelate complex formation with metal ions was evaluated by release of linzagolix from a cellulose membrane sac. In these in vitro studies, linzagolix showed no potential for insoluble precipitate formation under fasted/fed conditions and no chelate complex formation in the presence of metal ions. In rats, the plasma concentration-time profiles of linzagolix and iron ion were similar regardless of whether they were administered with or without ferrous sulfate and linzagolix choline at clinically relevant doses. Thus, linzagolix and iron ion had no effect on each other’s absorption in vivo. In conclusion, linzagolix is unlikely to cause clinically relevant drug-drug interactions by chelating metal ions according to the results of in vitro and in vivo studies.

Metal Chelators Ethylenediaminetetraacetic acid (EDTA) and N,N,N′,N′‐tetrakis(2‐pyridinylmethyl)‐1,2‐ethanediamine (TPEN) Interfere with Carbonic Anhydrase (CA) Activity in Wilbur‐Anderson Assay (WAa)

In our effort to set up a laboratory for undergraduate students with the tentative title ”Studying enzymatic activity of Carbonic Anhydrase”, we successfully determined carbonic anhydrase activity and demonstrated its inhibition by Acetazolamide, a potent CA inhibitor, using the Wilbur‐Anderson assay (WAa) using 6 experimental set‐ups with a class of 24 students.WAa hinges upon determining the time T (in seconds) required for 4 mL of saturated with carbon dioxide (CO2) water to lower pH from 8.3 to 6.3 of the mixture when added to 6 mL of 0.02M Tris buffer at 0°C without (T0) and with enzyme (TE). Activity (A) is defined as A = 2*(T0/TE‐1) assay units (AU). In n = 16 blank trials, T0 = 75.0±10.7s (Mean±Standard deviation), and with 0.001mg of CA in n = 12 trials, TE = 50.2±8.1s, A = 0.99±0.66 AU (p < 0.001). When for a test we used EDTA, a carboxylic high‐affinity metal ion chelator, to inactivate this Zn2+‐containing enzyme, we unexpectedly encountered that in the presence of the sodium salt of EDTA (Na2EDTA): 1) T was significantly slowed in a concentration‐dependent manner: for 5µM, 50µM, and 500µM, T was 84.3±7.9s (n = 10, p < 0.05), 108.5±.6s (n = 7, p < 0.001), and 130.8±22.7s (n = 10, p < 0.001), respectively; and 2) unexpectedly, in the context of the previous finding, Na2EDTA significantly enhanced CA activity (TE = 38.5±4.0s, A = 1.84 AU, n = 10, p < 0.001) in the presence of 5µM Na2EDTA that was abrogated by 10µM Acetazolamide, a potent CA inhibitor (T = 138.3±10.4s, n = 7, p < 0.001). TPEN, a pyridinic non‐carboxylic metal ion chelator that is more potent in metal ion chelation that EDTA, significantly slowed T0 (99.5±15.9s, n = 4) similar to Na2EDTA, and significantly enhance CA activity (TE = 41.1±3.8, n = 4, p < 0.05) with equal potency.This indicates that principally chemically different metal ion chelators EDTA and TPEN interfere with the determination of CA activity in the context of WAa. Studies to explain these phenomena are underway with the hypotheses that the contaminating metal ions that catalyze CO2 hydration/dehydration without CA are responsible for the observed phenomena.

Physicochemical properties, molecular structure, antioxidant activity, and biological function of extracellular melanin from Ascosphaera apis.

Ascosphaera apis spores containing a dark-colored pigment infect honeybee larvae, resulting in a large-scale collapse of the bee colony due to chalkbrood disease. However, little is known about the pigment or whether it plays a role in bee infection caused by A. apis. In this study, the pigment was isolated by alkali extraction, acid hydrolysis, and repeated precipitation. Ultraviolet (UV) analysis revealed that the pigment had a color value of 273, a maximum absorption peak at 195 nm, and a high alkaline solubility (7.67%) and acid precipitability. Further chemical structure analysis of the pigment, including elemental composition, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, mass spectrometry, and nuclear magnetic resonance (NMR), proved that it was a eumelanin with a typical indole structure. The molecular formula of melanin is C10H6O4N2, and its molecular weight is 409 Da. Melanin has hydroxyl, carboxyl, amino, and phenolic groups that can potentially chelate to metal ions. Antioxidant function analyses showed that A. apis melanin had a high scavenging activity against superoxide, hydroxyl, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, and a high reducing ability to Fe3+. Indirect immunofluorescence assay (IFA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses showed that A. apis melanin was located on the spore wall. The spore wall localization, antioxidant activity, and metal ion chelating properties of fungal melanin have been suggested to contribute to spore pathogenicity. However, further infection experiments showed that melanin-deficient spores did not reduce the mortality of bee larvae, indicating that melanin does not increase the virulence of A. apis spores. This study is the first report on melanin produced by A. apis, providing an important background reference for further study on its role in A. apis.

Synthesis and Antimalarial Activities of New Hybrid Atokel Molecules.

The currently spreading resistance of the malaria parasite Plasmodium falciparum to artemisinin‐based combination therapies makes an urgent need for new efficient drugs. Aiming to kill artemisinin‐resistant Plasmodium, a series of novel hybrid drugs named Atokels were synthesized and characterized. Atokels are based on an 8‐amino‐ or 8‐hydroxyquinoline entity covalently bound to a 1,4‐naphthoquinone through a polyamine linker. These drugs have been designed to target the parasite mitochondrion by their naphthoquinone moiety reminiscent of the antimalarial drug atovaquone, and to trigger a damaging oxidative stress due to their ability to chelate metal ions in order to generate redox active complexes in situ. The most effective Atokel drug shown a promising antimalarial activity (IC50=622 nm on an artemisinin‐resistant P. falciparum strain) and no cytotoxicity at 50 μm indicating a specific antiplasmodial mode of action.

Potential Use of Tannin Extracts as Additives in Semen Destined for Cryopreservation: A Review.

Simple SummaryFreezing of semen used for artificial reproductive technologies (ART) affects the survival and vigour of sperm cells due to excessive production of reactive oxygen species (ROS) during the freezing and thawing processes. ROS plays a physiological role in sperm function but excessive ROS production from damaged sperm cells can hinder sperm’s motility and their ability to fertilise an oocyte. Tannins, a class of water-soluble plant polyphenols, are known to have antioxidant and other health-promoting effects and may serve as binders/acceptors to reduce the deleterious effects of excessive ROS produced during the freezing and thawing process. This review is the first to analyse the available data supporting the use of tannins as additives to semen extenders to improve the survival of cryopreserved spermatozoa during storage and after thawing. It is concluded that tannins and their derivatives have naturally protective properties with the potential to ameliorate sperm cell survival after freezing.Cryopreservation and storage of semen for artificial insemination (AI) result in excessive accumulation of reactive oxygen species (ROS). This leads to a shortened life span and reduced motility of spermatozoa post-thawing, with consequent impairment of their function. However, certain levels of ROS are essential to facilitate the capacitation of spermatozoa required for successful fertilisation. Tannins, as well-known antioxidant compounds, may act as ROS binders/acceptors/scavengers to inhibit the damaging effects of ROS. This review comprises an analysis of the semen cryopreservation protocol and health functions of tannins, as well as the effects of ROS on fresh and cryopreserved semen’s longevity and fertilisation. Additionally, we surveyed available evidence of the effects of tannin extract feed supplementation on male fertility. We furthermore interrogated existing theories on tannin use as a potential additive to semen extenders, its relationship with semen quality, and to what degree existing theories have been investigated to develop testable new hypotheses. Emphasis was placed on the effects of tannins on ROS, their involvement in regulating sperm structure and function during cryopreservation, and on post-thaw sperm motility, capacitation, and fertilising ability. The diverse effects of tannins on the reproductive system as a result of their potential metal ion chelation, protein precipitation, and biological antioxidant abilities have been identified. The current data are the first to support the further investigation of the incorporation of tannin-rich plant extracts into semen extenders to enhance the post-thaw survival, motility, and fertilising ability of cryopreserved spermatozoa.