Radical scavenging property of a novel peptide derived from C-terminal SOD domain of superoxide dismutase enzyme in Arthrospira platensis

Microalgal proteins: Unveiling sustainable alternatives to address the protein challenge

Recent breakthroughs emphasized the considerable potential of microalgae as a sustainable protein source. Microalgae are regarded as a substitute for protein-rich foods because of their high protein and amino acid content. However, despite their nutritional value, microalgae cannot be easily digested by humans due to the presence of cell walls. In the subsequent sections, protein extraction technology, the overview of the inherent challenges of the process, and the summary of the factors affecting protein extraction and utilization have been deliberated. Moreover, the review inspected the formation of proteolytic products, highlighting their diverse bioactivities, including antioxidant, antihypertensive, and immunomodulatory activities. Finally, the discussion extended to the emerging microalgal protein sourced foods, such as baked goods and nutritional supplements, as well as the sensory and marketing challenges encountered in the production of microalgal protein foods. The lack of consumer awareness about the health benefits of microalgae complicates its acceptance in the market. Long-standing challenges, such as high production costs, persist. Currently, multi-product utilization strategies are being developed to improve the economic viability of microalgae. By integrating economic, environmental, and social factors, microalgae protein can be sustainably developed to provide a reliable source of raw materials for the future food industry.

TiO2 nanoparticles combined with polystyrene nanoplastics aggravated reproductive toxicity in female mice via exacerbating intestinal barrier disruption

BACKGROUND

TiO2 nanoparticles (NPs), a widely used food additive in the food industry, have been shown to aggravate the progress of metabolic diseases. Nanoplastics (NPLs) are an emerging contaminant widely present in the food system and have been shown to induce ovarian disorders in mammals. Noteworthy, they can be ingested by humans through 'contaminated' food, whereas the potential toxicity of NPLs and TiO2 NPs combined remains unclear. In the present study, we investigated the potential effects and mechanisms of co-exposure to polystyrene (PS) NPLs and TiO2 NPs on the ovary in female mice.

RESULTS

Our results revealed that the co-exposure of TiO2 NPs and PS NPLs caused significant injury to ovarian structure and function, but individual exposure had no effect. Moreover, compared to the TiO2 NPs group, co-exposure aggravated the intestinal barrier damage in mice, increasing the bioaccumulation of TiO2 NPs in the ovary. After being supplemented with the oxidative stress inhibitor N-acetyl-l-cysteine, the expression of ovarian antioxidant genes increased, and the ovarian structural and functional injury in co-exposure mice reverted to normal levels.

CONCLUSION

The present study demonstrated that co-exposure to PS NPLs and TiO2 NPs can cause more severe female reproductive dysfunction and deepens the toxicological insights between NPLs and NPs. © 2023 Society of Chemical Industry.

Antimicrobial Peptides from Photosynthetic Marine Organisms with Potential Application in Aquaculture

Aquaculture production is at a record level and is estimated to increase in the coming years. However, this production can be negatively affected by infectious diseases produced by viruses, bacteria, and parasites, causing fish mortality and economic losses. Antimicrobial peptides (AMPs) are small peptides that may be promising candidates to replace antibiotics because they are the first line of defense in animals against a wide variety of pathogens and have no negative effects; they also show additional activities such as antioxidant or immunoregulatory functions, which makes them powerful alternatives for use in aquaculture. Moreover, AMPs are highly available in natural sources and have already been used in the livestock farming and food industries. Photosynthetic marine organisms can survive under all kinds of environmental conditions and under extremely competitive environments thanks to their flexible metabolism. For this reason, these organisms represent a powerful source of bioactive molecules as nutraceuticals and pharmaceuticals, including AMPs. Therefore, in this study we reviewed the present knowledge about AMPs from photosynthetic marine organism sources and analyzed whether they could be suitable for use in aquaculture.

Integrated cascade catalysis of microalgal bioenzyme and inorganic nanozyme for anti-inflammation therapy

Combinations of multiple enzymes for cascade catalysis have been widely applied in biomedicine, but the integration of a natural bioenzyme with an inorganic nanozyme is less developed. Inspired by the abundant content of superoxide dismutase (SOD) in Spirulina platensis (SP), we establish an integrated cascade catalysis for anti-inflammation therapy by decorating catalase (CAT)-biomimetic ceria nanoparticles (CeO₂) onto the SP surface via electrostatic interaction to build microalgae-based biohybrids. The biohybrids exhibit combined catalytical competence for preferentially transforming superoxide anion radicals (O₂˙^-) to hydrogen peroxide (H₂O₂), and subsequently catalyzing H₂O₂ disproportionation to water and oxygen. In ulcerative colitis and Crohn's disease, the biohybrids reveal a satisfactory therapeutic effect owing to the synergistic reactive oxygen species (ROS)-scavenging capacity, suggesting a new train of thought for enzyme-based biomedical application.

Alleviating effects of pea peptide on oxidative stress injury induced by lead in PC12 cells via Keap1/Nrf2/TXNIP signaling pathway

Background

Lead poisoning causes an oxidative stress response – a key “bridge” connecting various pathways – in the human body. Oxidative stress usually implies an imbalance between pro-oxidants and antioxidants. Moreover, Nrf2, Keap1, and TXNIP proteins play an essential role in oxidative stress. Some studies showed that pea peptides could alleviate the oxidative stress response. However, the effect and mechanism of pea peptide on oxidative stress response induced by lead in PC12 cells has not been reported.

Aim

Investigating the effect and mechanism of pea peptides in alleviating oxidative damage in PC12 cells induced by lead.

Methods

In this study, cell viability was measured by CCK8 (Cell Counting Kit-8). Superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), reactive oxygen species (ROS), and lipid peroxidation (MDA) were measured using the corresponding Biochemical kits. The Keap1, Nrf2, and TXNIP protein expressions were tested using Western blot.

Results

Pea peptides PP3, PP4, and PP6 could reverse the decrease of cell viability caused by lead exposure (P < 0.05), the elevation of ROS and MDA caused by lead exposure, and the decrease of CAT, SOD, GR, GPx, and GSH/GSSG caused by lead exposure (P < 0.05). Moreover, PP3, PP4, and PP6 could reduce the elevated expression of Keap1 and TXNIP caused by lead exposure; and increase the expression of Nrf2 (P < 0.05).

Conclusion

PP3, PP4, and PP6 can alleviate lead-induced oxidative stress damage in PC12 cells, and the Nrf2/Keap1/TXNIP signaling pathway may play an essential role in this process.

3-Formylindole-based chitosan Schiff base polymer: Antioxidant and in vitro cytotoxicity studies on THP-1 cells

Two imine derivatives of chitosan (i-CTs), namely 2FCT and 5MCT, were synthesized by reacting chitosan (CT) with 2-(3-formyl-1H-indol-1yl)acetonitrile (2F), and 5-methoxyindole-3-carbaldehyde (5M), respectively. The antimicrobial evaluation of i-CTs exhibited stronger inhibition effect against Staphylococcus aureus, Escherichia coli and Candida albicans. The antioxidant activity of 2FCT and 5MCT showed strong scavenging ability with IC₅₀ 2.31 and 6.92 μg/mL, respectively. The results of in vitro cytotoxicity of 2FCT and 5MCT examined using human monocyte leukemia (THP-1) cells indicate no cytotoxic effect on host cells and the value of cell viability was found to be 87.08 and 84.47%, respectively. Measurement of intracellular Reactive Oxygen Species (ROS) production by flow cytometry analysis revealed that the 2FCT and 5MCT reduced the ROS generation by 83 and 43%, respectively. In summary, these findings show that i-CTs synthesized to be promising biomaterial for biomedical applications such as wound healing.

Antioxidant Peptides From Protein Hydrolysate of Marine Red Algae Eucheuma cottonii: Preparation, Identification, and Cytoprotective Mechanisms on H2O2 Oxidative Damaged HUVECs

To screen, prepare, identify, and evaluate the activities of natural antioxidants for treating chronic diseases caused by oxidative stress. Two algal proteins, namely ZD10 and ZD60, precipitated with 10 and 60% (NH₄)₂SO₄ were extracted from red algae Eucheuma cottonii (E. cottonii) and hydrolyzed using five proteolytic enzymes. The results showed that ZD60 played the most significant role in the enhancement of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH⋅) scavenging activity (25.91 ± 0.24%) among all protein hydrolysates. Subsequently, six antioxidant peptides (EP1-EP6) were isolated from the papain hydrolysate of ZD60 by ultrafiltration and chromatography methods. Their amino acid sequences were identified as Thr-Ala (EP1), Met-Asn (EP2), Tyr-Ser-Lys-Thr (EP3), Tyr-Ala-Val-Thr (EP4), Tyr-Leu-Leu (EP5), and Phe-Tyr-Lys-Ala (EP6) with molecular weights of 190.21, 263.33, 497.55, 452.51, 407.51, and 527.62 Da, respectively. Of which, EP3, EP4, EP5, and EP6 showed strong scavenging activities on DPPH⋅, hydroxyl radical (HO⋅), and superoxide anion radical (O- 2⋅). Moreover, EP4 and EP5 could significantly protect human umbilical vein endothelial cells (HUVECs) from H₂O₂-induced oxidative damage by increasing the levels of antioxidant enzyme systems including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to reduce the levels of reactive oxygen species (ROS) (60.51 and 51.74% of model group) and malondialdehyde (MDA) (75.36 and 64.45% of model group). In addition, EP4 and EP5 could effectively inhibit H₂O₂-induced apoptosis by preventing HUVECs from early apoptosis to late apoptosis. These results indicated that the antioxidant peptides derived from E. cottonii, especially EP4 and EP5, could serve as the natural antioxidants applied in pharmaceutical products to treat chronic cardiovascular diseases caused by oxidative damage, such as coronary heart disease, atherosclerosis, etc.

A hepatic antimicrobial peptide, hepcidin from Indian major carp, Catla catla: molecular identification and functional characterization

Background

Increase of antibiotic resistance in pathogenic microbes necessitated novel molecules for curing infection. Antimicrobial peptides (AMPs) are the gene-encoded evolutionarily conserved small molecules with therapeutic value. AMPs are considered as an alternative drug for conventional antibiotics. Hepcidin, the cysteine-rich antimicrobial peptide, is an important component in innate immune response. In this study, we identified and characterized hepcidin gene from the fish, Catla catla (Indian major carp) and termed it as Cc-Hep.

Results

Open reading frame of Cc-Hep consists of 261 base pair that encodes 87 amino acids. Cc-Hep is synthesized as a prepropeptide consisting of 24 amino acid signal peptide, 36 amino acid propeptide, and 26 amino acid mature peptide. Sequence analysis revealed that Cc-Hep shared sequence similarity with hepcidin from Sorsogona tuberculata. Phylogenetic analysis indicated that Cc-Hep was grouped with HAMP2 family. Structure analysis of mature Cc-Hep identified two antiparallel beta sheets stabilized by four disulphide bonds and a random coil. The mature peptide region of Cc-Hep has a charge of + 2, isoelectric value 8.23 and molecular weight 2.73 kDa.

Conclusion

Functional characterization predicted antibacterial, antioxidant, and anticancer potential of Cc-Hep, which can be explored in aquaculture or human health care.

6-Gingerol and Semisynthetic 6-Gingerdione Counteract Oxidative Stress Induced by ROS in Zebrafish

6-Gingerol (1) is one of the major components in ginger and developing new synthetic methodologies could bring semisynthetic analogs with improved therapeutic properties. Towards this, multigram scale isolation of 6-gingerol with excellent purity was optimized using a simple and robust extraction, followed by column purification. Synthesis of 6-gingerdione, 7 from 6-gingerol was then achieved through selective -OTBDMS protection, DMP oxidation and deprotection reaction sequence for the first time. Compounds 1, 7 and 8 (dehydrozingerone) exhibited excellent cell-free antioxidant properties in DPPH, ABTS, superoxide radical scavenging assay and H2 O2 assay at 10-50 μM concentrations. The hemolytic study suggests that up to 50 μM, all three compounds did not exhibit toxicity to human erythrocytes. When H2 O2 treated zebrafish larvae groups (96hpf) were exposed to compounds 1, 7 and 8, it increases the SOD (19, 19.1 and 18.7 U/mg protein), CAT (18.1, 16.5, and 15.8 μmol/mg levels and decreases the lipid peroxidation level (13, 15 and 18 nmol/mg protein), respectively. In vivo ROS levels and degree of cell death were studied using DCFDA and Acridine orange assays. Compounds 1, 7 and 8 decreases the ROS and cell death level significantly. Taken together, compounds 1, 7 and 8 exhibit excellent antioxidant properties, counteract H2 O2 induced oxidative stress, reduces cell death in zebrafish larvae.

RM12 similar to substance P from tachykinin of freshwater murrel Channa striatus influence intracellular ROS in vitro fish erythrocytes and developmental toxicity and antioxidant enzymes in vivo zebrafish embryo

In this study, substance P, an antioxidant peptide of tachykinin, was identified using bioinformatics tools from the earlier established muscle transcriptome of a freshwater murrel Channa striatus and the peptide was named RM12. The antioxidant properties of RM12 were screened using various colorimetric assays. The toxicity of RM12 was experimented using fish erythrocytes, and it is observed that the maximum concentration (320 μM) of RM12 was found to have 15 or 20% of hemolytic activity; however, it was not significant with other tested concentrations (10, 20, 40, 80, and 160 μM). Further, the in vivo antioxidant properties of RM12 were experimented on zebrafish embryo, the intracellular ROS level was estimated by 5 mM H₂O₂ stress in the zebrafish embryo, and inhibition of apoptosis was evaluated. The antioxidant enzymes were extracted from the H₂O₂-stressed zebrafish embryo, and the intracellular ROS was eliminated due to RM12. Collectively, the experiment showed that the substance P from the freshwater murrel C. striatus possessed potent antioxidant properties; thus, it can further be focused to develop it as antioxidant molecule in aquaculture organisms.

NV14 from serine O-acetyltransferase of cyanobacteria influences the antioxidant enzymes in vitro cells, gene expression against H2 O2 and other responses in vivo zebrafish larval model

In this study, we have identified a novel peptide NV14 with antioxidative functions from serine O-acetyltransferase (SAT) of Artrospira platensis (Ap). The full sequence of ApSAT and its derived NV14 peptide "NVRIGAGSVVLRDV" (141-154) was characterized using bioinformatics tools. To address the transcriptional activity of ApSAT in response to induce generic oxidative stress, the spirulina culture was exposed to H₂ O₂ (10 mM). The ApSAT expression was studied using RT-PCR across various time points and it was found that the expression of the ApSAT was significantly upregulated on Day 15. The in vitro cytotoxicity assay against NV14 was performed in human dermal fibroblast cells and human blood leukocytes. Results showed that NV14 treatment was non-cytotoxic to the cells. Besides, in vivo treatment of NV14 in zebrafish larvae did not exhibit the signs of developmental toxicity. Further, the in vitro antioxidant assays enhanced the activity of the antioxidant enzymes, such as SOD and CAT, due to NV14 treatment; and also significantly reduced the MDA levels, while increasing the superoxide radical and H₂ O₂ scavenging activity. The expression of antioxidant enzyme genes glutathione peroxidase, γ-glutamyl cysteine synthase, and glutathione S-transferase were found to be upregulated in the NV14 peptide pretreated zebrafish larvae when induced with generic oxidative stress, H₂ O₂ . Overall, the study showed that NV14 peptide possessed potent antioxidant properties, which were demonstrated over both in vitro and in vivo assays. NV14 enhanced the expression of antioxidant enzyme genes at the molecular level, thereby modulating and reversing the cellular antioxidant balance disrupted due to the H₂ O₂ -induced oxidative stress.

Deteriorating insulin resistance due to WL15 peptide from cysteine and glycine-rich protein 2 in high glucose-induced rat skeletal muscle L6 cells

This study investigates the antioxidant and antidiabetic activity of the WL15 peptide derived from Channa striatus on regulating the antioxidant property in the rat skeletal muscle cell line (L6) and enhancing glucose uptake via glucose metabolism. Increased oxidative stress plays a major role in the development of diabetes and its complications. Strategies are needed to mitigate the oxidative stress that can reduce these pathogenic processes. Our results showed that with treatment with WL15 peptide, the reactive oxygen species significantly decreased in L6 myotubes in a dose-dependent manner, and increased antioxidant enzymes help to prevent the formation of lipid peroxidation in L6 myotubes. The cytotoxicity of WL15 is evaluated in the L6 cells and found to be non-cytotoxic at the tested concentration. Also, for the analysis of glucose uptake activity in L6 cells, the 2-(N-[7-nitrobenz-2-oxa-1,3-diazol-4-yl]amino)-2-deoxy- d -glucose assay was performed in the presence of wortmannin and genistein inhibitors. WL15 demonstrated antidiabetic activities through a dose-dependent increase in glucose uptake (64%) and glycogen storage (7.8 mM). The optimal concentration for the maximum activity was found to be 50 µM. In addition, studies of gene expression in L6 myotubes demonstrated upregulation of antioxidant genes and genes involved in the pathway of insulin signaling. In cell-based assays, WL15 peptide decreased intracellular reactive oxygen species levels and demonstrated insulin mimic activity by enhancing the primary genes involved in the insulin signaling pathway by increased glucose uptake indicating that glucose transporter type 4 (GLUT4) is regulated from the intracellular pool to the plasma membrane.

Tryptophan-tagged peptide from serine threonine-protein kinase of Channa striatus improves antioxidant defence in L6 myotubes and attenuates caspase 3-dependent apoptotic response in zebrafish larvae

This study reports the antioxidant property and molecular mechanism of a tryptophan-tagged peptide derived from a teleost fish Channa striatus of serine threonine-protein kinase (STPK). The peptide was tagged with tryptophan to enhance the antioxidant property of STPK and named as IW13. The antioxidant activity of IW13 peptide was investigated using in vitro methods such as DPPH, ABTS, superoxide anion radical scavenging and hydrogen peroxide scavenging assay. Furthermore, to investigate the toxicity and dose response of IW13 peptide on antioxidant defence in vitro, L6 myotubes were induced with generic oxidative stress due to exposure of hydrogen peroxide (H₂O₂). IW13 peptide exposure was found to be non-cytotoxic to L6 cells in the tested concentration (10, 20, 30, 40 and 50 μM). Also, the pre-treatment of IW13 peptide decreased the lipid peroxidation level and increased glutathione enzyme activity. IW13 peptide treatment upregulated the antioxidant enzyme genes: GPx (glutathione peroxidase), GST (glutathione S transferase) and GCS (glutamine cysteine synthase), in vitro in L6 myotubes and in vivo in zebrafish larvae against the H₂O₂-induced oxidative stress. The results demonstrated that IW13 renders protection against the H₂O₂-induced oxidative stress through a cellular antioxidant defence mechanism by upregulating the gene expression, thus enhancing the antioxidant activity in the cellular or organismal level. The findings exhibited that the tryptophan-tagged IW13 peptide from STPK of C. striatus could be a promising candidate for the treatment of oxidative stress-associated diseases.

Intracellular ROS scavenging and antioxidant regulation of WL15 from cysteine and glycine-rich protein 2 demonstrated in zebrafish in vivo model

Antioxidant peptides are naturally present in food, especially in fishes, and are considered to contain rich source of various bioactive compounds that are structurally heterogeneous. This study aims to identify and characterize the antioxidant property of the WL15 peptide, derived from Cysteine and glycine-rich protein 2 (CSRP2) identified from the transcriptome of a freshwater food fish, Channa striatus. C. striatus is already studied to contain high levels of amino acids and fatty acids, besides traditionally known for its pharmacological benefits in the Southeast Asian region. In our study, in vitro analysis of WL15 peptide exhibited strong free radical scavenging activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), superoxide anion radical and hydrogen peroxide (H2O2) scavenging assay. Further, to evaluate the cytotoxicity and dose-response, the Human dermal fibroblast (HDF) cells were used. Results showed that the treatment of HDF cells with varying concentrations (10, 20, 30, 40 and 50 μM) of WL15 peptide was not cytotoxic. However, the treatment concentrations showed enhanced antioxidant properties by significantly inhibiting the levels of free radicals. For in vivo assessment, we have used zebrafish larvae for evaluating the developmental toxicity and for determining the antioxidant property of the WL15 peptide. Zebrafish embryos were treated with the WL15 peptide from 4 h of post-fertilization (hpf) to 96 hpf covering the embryo-larval developmental period. At the end of the exposure period, the larvae were exposed to H2O2 (1 mM) for inducing generic oxidative stress. The exposure of WL15 peptide during the embryo-larval period showed no developmental toxicity even in higher concentrations of the peptide. Besides, the WL15 peptide considerably decreased the intracellular reactive oxygen species (ROS) levels induced by H2O2 exposure. WL15 peptide also inhibited the H2O2-induced caspase 3-dependent apoptotic response in zebrafish larvae was observed using the whole-mount immunofluorescence staining. Overall results from our study showed that the pre-treatment of WL15 (50 μM) in the H2O2-exposed zebrafish larvae, attenuated the expression of activated caspase 3 expressions, reduced Malondialdehyde (MDA) levels, and enhanced antioxidant enzymes, including superoxide dismutase (SOD) and catalase (CAT). The gene expression of antioxidant enzymes such as glutathione S-transferase (GST), glutathione peroxide (GPx) and γ-glutamyl cysteine synthetase (GCS) was found to be upregulated. In conclusion, it can be conceived that pre-treatment with WL15 could mitigate H2O2-induced oxidative injury by elevating the activity and expression of antioxidant enzymes, thereby decreasing MDA levels and cellular apoptosis by enhancing the antioxidant response, demonstrated by the in vitro and in vivo experiments.

Extraction of flavanones from immature Citrus unshiu pomace: process optimization and antioxidant evaluation

Dietary guidelines recommend the consumption of flavonoid-rich extracts for several health benefits. Although immature Citrus unshiu pomace (ICUP) contains high levels of flavanone glycosides, many studies have concentrated on the optimization of flavonoid extraction from mature citrus peels. Therefore, we developed an optimized extraction method for hesperidin and narirutin from ICUP, and evaluated their antioxidant activities using ten different assay methods. The extraction conditions for the highest flavonoid yields based on a response surface methodology were 80.3 °C, 58.4% (ethanol concentration), 40 mL/g (solvent/feed), and 30 min, where the hesperidin and narirutin yields were 66.6% and 82.3%, respectively. The number of extractions was also optimized as two extraction steps, where the hesperidin and narirutin yields were 92.1% and 97.2%, respectively. Ethanol was more effective than methanol and acetone. The ethanol extract showed high scavenging activities against reactive oxygen species but relatively low scavenging activities for nitrogen radicals and reactive nitrogen species. The antioxidant activities showed a higher correlation with hesperidin content than narirutin content in the extracts. This study confirms the potential of an optimized method for producing antioxidant-rich extracts for the functional food and nutraceutical industries.

TL15 of Arthrospira platensis sulfite reductase scavenges free radicals demonstrated in oxidant induced larval zebrafish (Danio rerio) model

The antioxidant role of sulfite reductase (SiR) derived from Arthrospira platensis (Ap) was identified through a short peptide, TL15. The study showed that the expression of ApSiR was highly expressed on day ten due to sulfur deprived stress in Ap culture. TL15 peptide exhibited strong antioxidant activity when evaluated using antioxidant assays in a concentration ranging from 7.8 and 125 μM. Further, the cytotoxicity of TL15 peptide was investigated, even at the higher concentration (250 μM), TL15 did not exhibit any toxicity, when tested in vitro using human leucocytes. Moreover, a potential reduction in reactive oxygen species (ROS) production was observed due to the treatment of TL15 peptide (>15.6 μM) to H₂O₂ exposed leucocytes. For the in vivo assessment of TL15 toxicity and antioxidant ability, experiments were performed in zebrafish (Danio rerio) larvae to analyse the developmental toxicity of TL15 peptide. Results showed that, exposure to TL15 peptide in tested concentrations ranging from 10, 20, 40, and 80 μM, did not affect the development and physiological parameters of the zebrafish embryo/larvae such as morphology, survival, hatching and heart rate. Fluorescent assay was performed using DCFH-DA (2,7-dichlorodihydrofluorescein diacetate) to examine the production of intracellular reactive oxygen species (ROS) in zebrafish treated with TL15 peptide during the embryo-larval stages. Fluorescent images showed that pre-treatment with TL15 peptide to attenuate the H₂O₂ induced ROS levels in the zebrafish larvae in a dose-dependent manner. Further to uncover the underlying biochemical and antioxidant mechanism, the enzyme activity of superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation (LPO) levels were studied in zebrafish larvae. TL15 pre-treated groups showed enhanced antioxidant enzyme activity, while the hydrogen peroxide (H₂O₂) exposed larvae showed significantly diminished activity. Overall results from the study revealed that, TL15 act as a potential antioxidant molecule with dose-specific antioxidant property. Thus, TL15 peptide could be an effective and promising source for biopharmaceutical applications.

Peroxiredoxin of Arthrospira platensis derived short molecule YT12 influences antioxidant and anticancer activity

This study demonstrates both the antioxidant and anticancer potential of the novel short molecule YT12 derived from peroxiredoxin (Prx) of spirulina, Arthrospira platensis (Ap). ApPrx showed significant reduction in reactive oxygen species (ROS) against hydrogen peroxide (H₂ O₂ ) stress. The complementary DNA sequence of ApPrx contained 706 nucleotides and its coding region possessed 546 nucleotides between position 115 and 660. Real-time quantitative reverse transcription polymerase chain reaction analysis confirmed the messenger RNA expression of ApPrx due to H₂ O₂ exposure in spirulina cells at regular intervals, in which the highest expression was noticed on Day 20. Cytotoxicity assay was performed using human peripheral blood mononuclear cells, and revealed that at 10 μM, the YT12 did not exhibit any notable toxicity. Furthermore, ROS scavenging activity of YT12 was performed using DCF-DA assay, in which YT12 scavenged a significant amount of ROS at 25 μM in H₂ O₂ -treated blood leukocytes. The intracellular ROS in human colon adenocarcinoma cells (HT-29) was regulated by oxidative stress, where the YT12 scavenges ROS in HT-29 cells at 12.5 μM. Findings show that YT12 peptide has anticancer activity, when treated against HT-29 cells. Through the MTT assay, YT12 showed vital cytotoxicity against HT-29 cells. These finding suggested that YT12 is a potent antioxidant molecule which defends ROS against oxidative stress and plays a role in redox balance.

CxxC Zinc Finger Protein Derived Peptide, MF18 Functions Against Biofilm Formation

The major threat in modern medicine was biofilm forming bacterial related infections and they were highly tolerant to conventional antibiotics and a boundless demand for new drugs. In this regard, antimicrobial peptide (AMP) have been considered as potential alternative agents to conventional antibiotics. In this study, we have reported a CxxC zinc finger protein derived peptide, MF18 and its various biological role including activity against biofilm forming bacteria. Zinc finger protein are important in regulation of several cellular processes and wide range of molecular functions. The CxxC zinc finger protein identified from the cDNA library of a teleost fish; further it was characterised using various online bioinformatics programs. During the in-silico analysis, an AMP named MF18 was identified from the CxxC zinc finger protein, then it was synthesised for further biological activity studies. The antimicrobial activity of MF18 was confirmed against the biofilm clinical isolates such as Staphylococcus aureus and Escherichia coli. The MIC of the antimicrobial peptide at the concentration of 320 µM was observed against these two biofilm bacteria. The mechanism of the peptides was determined using bacteria on its membrane permeabilization ability by scanning electron microscopy. It is exhibited that the MF18 potentially influenced in damaging the morphology of the bacteria. The toxicity of MF18 against the continuous cell line (RAW 264.7) was demonstrated by MTT assay and also using peripheral red blood cells by haemolytic assay; both assays showed that the peptide have no toxicity on the cells at lower concentration. Overall, the study showed the potential therapeutic application of the peptide in pharma industry.

Intracellular oxidative damage due to antibiotics on gut bacteria reduced by glutathione oxidoreductase-derived antioxidant molecule GM15

The human gut consists of > 1000 different bacterial species for the smooth functioning of the gut. In normal conditions, the antioxidant system present in cells minimize the effects of reactive oxygen species. Upon exposure to antibiotics, there is a rise in ROS level which induces oxidative stress to the cells, ultimately killing the cells. Two broad-spectrum antibiotics, streptomycin and gentamicin at a concentration of 50 µM and 25 µM, were treated with Bacillus subtilis SRMIST201901 (MN726522) and B. cereus SRMIST201902 (MN726923); the treatment reduced the cell counts. Considering the bacterial defense property which relies on the antioxidant mechanism, in this study, we have reported an antioxidant peptide (GM15) derived from glutathione oxidoreductase of spirulina (or called cyanobacteria) Arthrospira platensis (Ap) which reduced the intracellular oxidative stress. Cellular ROS detection was confirmed by fluorescent-associated cell sorting (FACS) using the DCFDA dye. Resazurin dye test also confirmed the activity of peptide on the growth of the Bacillus sp. Based on the results obtained, it was concluded that there was a significant (P < 0.05) reduction in the intracellular oxidative stress on treating with GM15 peptide. Overall, the study indicates the influence of antioxidant peptide on the intracellular oxidative stress, leading to the development of an antioxidant drug from glutathione oxidoreductase of A. platensis against oxidative-related stresses.

Antioxidant molecular mechanism of adenosyl homocysteinase from cyanobacteria and its wound healing process in fibroblast cells

An antioxidant molecule namely, adenosyl homocysteinase (AHc) was identified from the earlier constructed transcriptome database of Spirulina, where it was cultured in a sulphur deprived condition. From the AHc protein, a small peptide NL13 was identified using bioinformatics tools and was predicted to have antioxidant property. Further, the peptide was synthesised and its antioxidant mechanism was addressed at molecular level. NL13 was subjected to various antioxidant assays including DPPH assay, HARS assay, SARS Assay, NO assay and ABTS assay, where NL13 exhibited significant (P < 0.05) potential antioxidant activity compared to its antioxidant control, Trolox. Cytotoxicity was performed on Human whole blood and the cell viability was performed on VERO fibroblast cells. In both assays, it was found that NL13 did not exhibit any cytotoxic effect towards the cells. Further, the intracellular ROS was performed on Multimode reader followed by imaging on fluorescence microscope which showed scavenging activity even at lower concentration of NL13 (31.2 µM). An effective wound healing property of NL13 on VERO cells was confirmed by analysing the cell migration rate at two different time intervals (24 and 48 h). Overall, the study shows that NL13 peptide scavenges the intracellular oxidative stress.

High-Efficiency Catalysis of Peroxymonosulfate by MgO for the Degradation of Organic Pollutants

In the study, magnesium oxide (MgO) was used to catalyze peroxymonosulfate (PMS) for the degradation of organic pollutants for the first time. According to the single-factor experiment results, it was determined that MgO could efficiently catalyze PMS to degrade organic matters in a wide range of pH values. Based on radical quenching experiments and electron spinning resonance spectra, singlet oxygen was identified to be the crucial reactive species. Importantly, the oxygen vacancy on the surface of MgO was determined as the key active site, which accelerated the decomposition of PMS to produce singlet oxygen. This study provides an interesting insight into the novel and ignored catalyst of MgO for the highly efficient activation of PMS, which will greatly benefit the Fenton-like catalytic degradation of organic wastewater.

Optimization and Identification of Antioxidant Peptide from Underutilized Dunaliella salina Protein: Extraction, In Vitro Gastrointestinal Digestion, and Fractionation

DPPH• scavenging peptides (<3kDa) from underutilized Dunaliella salina protein were obtained by the following successive treatment, i.e., ultrasound extraction, simulated in vitro gastrointestinal digestion hydrolyzation, and membrane ultrafiltration classification. The optimal condition for ultrasound-assisted extraction was an ultrasound wave with 800 W of power treating a mixture of 60 mL of 1.0 mol L⁻¹ NaOH and 2 g algae powder for 15 min. A high correlation (r=0.8146) between DPPH• scavenging activity and yield of the intact peptides showed their antioxidant capacity. Simulated in vitro digestion assay resulted in excellent DPPH• scavenging activity of the total peptide, amounting to (86.5 ± 10.1)%, comparing with the nondigestion samples at (46.8 ± 6.5)%. After fractionation, the 500-1000 Da fraction exhibited the highest DPPH• scavenging activity (81.2 ± 4.0)%, increasing 1.5 times due to digestion. Then, the 500-1000 Da fraction was analyzed by RPLC-Q Exactive HF mass spectrometer, and 4 novel peptides, i.e., Ile-Leu-Thr-Lys-Ala-Ala-Ile-Glu-Gly-Lys, Ile-Ile-Tyr-Phe-Gln-Gly-Lys, Asn-Asp-Pro-Ser-Thr-Val-Lys, and Thr-Val-Arg-Pro-Pro-Gln-Arg, were identified. From these amino acid sequences, hydrophobic residues accounted for 56%, which indicated their high antioxidant property. The results indicated that underutilized protein of Dunaliella salina could be a potential source of antioxidative peptides through simulated in vitro gastrointestinal digestion.

Design and characterization of a novel Arthrospira platensis glutathione oxido-reductase-derived antioxidant peptide GM15 and its potent anti-cancer activity via caspase-9 mediated apoptosis in oral cancer cells

Glutathione oxido-reductase (GR) is a primary antioxidant enzyme of most living forms which protects the cells from oxidative metabolism by reducing glutathione (GSH) from its oxidized form (GSSG). Although the antioxidant role of the enzyme is well characterized, the specific role of conserved N' peptide sequence in antioxidant mechanism remains unclear. In this study, we have identified an RNA sequence encoding GR enzyme from spirulina, Arthrospira platensis (Ap) and the changes in its gene expression profile was analysed during H₂O₂ stress. Results showed that H₂O₂ (10 mM) stimulated the expression of ApGR throughout the timeline of study (0, 5, 10, 15 and 20 days) with highest expression at 5^th day post-exposure which confirmed the antioxidant role of ApGR in spirulina during H₂O₂ induced oxidative stress. A dithiol containing short antioxidant peptide, ³⁹GGTCVIRGCVPKKLM⁵³ (GM15) from ApGR was predicted and its radicals (superoxide and hydroxyl radical) scavenging potential was confirmed by in vitro cell-free assays. GM15 (12.5 μM) reduced the intracellular generalized oxidative stress level, as measured using DCFDA assay in H₂O₂ exposed leucocytes without affecting any of the cellular population. Further, the biomedical application of the radical scavenging property of GM15 was validated in oral carcinoma (KB) cells where GM15 exhibited significant cytotoxicity. Also, GM15 exhibited heterogenous effects on intracellular oxidative stress level in KB cells: at lower concentration (6.25 μM), the peptide reduced oxidative stress whereas, at higher concentration (25 μM) it increased the intensity of oxidative stress. GM15 (25 μM) induced caspase-9 mediated apoptosis in KB cells along with membrane disruption and DNA degradation which are confirmed by propidium iodide (PI) internalization and comet assays, respectively. Overall, the study shows that GM15 peptide i) scavenges superoxide, hydroxyl radicals, and influences intracellular oxidative stress, and ii) has anti-cancer effect in oral cancer cells.