Phytochemicals in antiviral drug development against human respiratory viruses.

This review explores the potential antiviral properties of various plant-based compounds, including polyphenols, phytochemicals, and terpenoids. It emphasizes the diverse functionalities of compounds such as epigallocatechin-3-gallate (EGCG), quercetin, griffithsin (GRFT,) resveratrol, linalool, and carvacrol in the context of respiratory virus infections, including SARS-CoV-2. Emphasizing their effectiveness in modulating immune responses, disrupting viral envelopes, and influencing cellular signaling pathways, the review underlines the imperative for thorough research to establish safety and efficacy. Additionally, the review underscores the necessity of well-designed clinical trials to evaluate the efficacy and safety of these compounds as potential antiviral agents. This approach would establish a robust framework for future drug development efforts focused on bolstering host defense mechanisms against human respiratory viral infections.

Metal sequestration by Microcystis extracellular polymers: a promising path to greener water treatment.

The problem of heavy metal pollution in water bodies poses a significant threat to both the environment and human health, as these toxic substances can persist in aquatic ecosystems and accumulate in the food chain. This study investigates the promising potential of using Microcystis aeruginosa extracellular polymeric substances (EPS) as an environmentally friendly, highly efficient solution for capturing copper (Cu2+) and nickel (Ni2+) ions in water treatment, emphasizing their exceptional ability to promote green technology in heavy metal sequestration. We quantified saccharides, proteins, and amino acids in M. aeruginosa biomass and isolated EPS, highlighting their metal-chelating capabilities. Saccharide content was 36.5 mg g-1 in biomass and 21.4 mg g-1 in EPS, emphasizing their metal-binding ability. Proteins and amino acids were also prevalent, particularly in EPS. Scanning electron microscopy (SEM) revealed intricate 3D EPS structures, with pronounced porosity and branching configurations enhancing metal sorption. Elemental composition via energy dispersive X-ray analysis (EDAX) identified essential elements in both biomass and EPS. Fourier transform infrared (FTIR) spectroscopy unveiled molecular changes after metal treatment, indicating various binding mechanisms, including oxygen atom coordination, π-electron interactions, and electrostatic forces. Kinetic studies showed EPS expedited and enhanced Cu2+ and Ni2+ sorption compared to biomass. Thermodynamic analysis confirmed exothermic, spontaneous sorption. Equilibrium biosorption studies displayed strong binding and competitive interactions in binary metal systems. Importantly, EPS exhibited impressive maximum sorption capacities of 44.81 mg g-1 for Ni2+ and 37.06 mg g-1 for Cu2+. These findings underscore the potential of Microcystis EPS as a highly efficient sorbent for heavy metal removal in water treatment, with significant implications for environmental remediation and sustainable water purification.

Potential of Scenedesmus-fabricated ZnO nanorods in photocatalytic reduction of methylene blue under direct sunlight: kinetics and mechanism.

Organic synthetic dyes are widely used in several industries; however, their inherent resistance to biodegradation necessitates to investigate alternative methods for the remediation of this class of hazardous substances. In the present study, a green synthesis of ZnO nanorods was achieved in a fast, environment-friendly, and safe microwave process employing algal extract. Different metabolites like sugars, proteins, fatty acids, amino acids, and vitamins present in the algal extract reduced the Zn2+ into ZnO. The XRD analysis showed that the nanostructure was a crystalline hexagonal nanorod having a crystalline size of 27.37 nm. The XPS spectra of ZnO nanorod showed characteristic peaks at binding energy 1043, 1020, 496, 137, 87, and 8 eV corresponding to Zn2p1/2, Zn2p3/2, ZnLMM, Zn3s, Zn3p, Zn3d, respectively. The synthesized ZnO nanorods were in-situ functionalized and showed strong catalytic activity in photoreduction of a model organic dye methylene blue (MB) under direct sunlight irradiation. Synthesized ZnO nanorods showed a complete (100%) reduction of model dye MB from its 10 mg/L aqueous solution. The photocatalytic degradation of MB followed the Michaelis-Menten kinetics. The rate of ZnO-catalyzed photocatalytic degradation depends on the concentrations of ZnO, pH, and sunlight irradiation. The ZnO nanorod-catalyzed photoreduction of MB involves hydroxyl radicals. Algal-mediated and microwave-assisted synthesis provides a scalable source of metal oxide nanoparticles for the remediation of dye-containing wastewaters under natural sunlight. Apart from application in the removal of dyes, ZnO nanorods are excellent material for applications in semiconductors, electronics, optics, bio-imaging, and drug delivery.

Accumulation and cellular toxicity of engineered metallic nanoparticle in freshwater microalgae: Current status and future challenges.

Metal nanoparticles (MNPs) are employed in a variety of medical and non-medical applications. Over the past two decades, there has been substantial research on the impact of metallic nanoparticles on algae and cyanobacteria, which are at the base of aquatic food webs. In this review, the current status of our understanding of mechanisms of uptake and toxicity of MNPs and metal ions released from MNPs after dissolution in the surrounding environment were discussed. Also, the trophic transfer of MNPs in aquatic food webs was analyzed in this review. Approximately all metallic nanoparticles cause toxicity in algae. Predominantly, MNPs are less toxic compared to their corresponding metal ions. There is a sufficient evidence for the trophic transfer of MNPs in aquatic food webs. Internalization of MNPs is indisputable in algae, however, mechanisms of their transmembrane transport are inadequately known. Most of the toxicity studies are carried out with solitary species of MNPs under laboratory conditions rarely found in natural ecosystems. Oxidative stress is the primary toxicity mechanism of MNPs, however, oxidative stress seems a general response predictable to other abiotic stresses. MNP-specific toxicity in an algal cell is yet unknown. Lastly, the mechanism of MNP internalization, toxicity, and excretion in algae needs to be understood carefully for the risk assessment of MNPs to aquatic biota.

Copper-induced proline synthesis is associated with nitric oxide generation in Chlamydomonas reinhardtii.

Excess copper affects the growth and metabolism of plants and green algae. However, the physiological processes under Cu stress are largely unknown. In this study, we investigated Cu-induced nitric oxide (NO) generation and its relationship to proline synthesis in Chlamydomonas reinhardtii. The test alga accumulated a large amount of proline after exposure to relatively low Cu concentrations (2.5 and 5.0 microM Cu2+). A concomitant increase in the intracellular NO level was observed with increasing concentrations of Cu applied. Data analysis revealed that the endogenous NO generated was positively associated with the proline level in Cu-stressed algae. The involvement of NO in Cu-induced proline accumulation was confirmed by using an NO-specific donor, sodium nitroprusside (SNP), and an NO scavenger cPTIO [2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylinidazoline-1-oxyl-3-oxide]. Pre-treatment with 10 microM SNP increased the proline accumulation in Cu-treated cells by about 1.5-fold, while this effect could be blocked by addition of 10 microM cPTIO. We further investigated the effect of Cu and NO on the activity and transcript amount of Delta(1)-pyrroline-5-carboxylate synthetase (P5CS, EC 2.7.2.11), the key enzyme of proline biosynthesis, and observed that application of SNP was able to stimulate the P5CS activity and up-regulate the expression of P5CS in the Cu-treated algae. These results indicate that Cu-responsive proline synthesis is closely related to NO generation in C. reinhardtii, suggesting the regulatory function of NO in proline metabolism under heavy metal stress.

Metabolic adaptations to mercury-induced oxidative stress in roots of Medicago sativa L.

Alfalfa (Medicago sativa) roots were treated with mercuric ions in a concentration- and time-dependent manner, and lipid peroxidation was studied biochemically as well as histochemically along with other physiological responses. Histochemical staining with Schiff's reagent and Evans blue revealed that the peroxidation of membrane lipids and loss of plasma membrane integrity in Hg-treated roots occurred in the meristem and the elongation zone. The histochemical observations were supported by the quantitative determinations of thiobarbituric acid reactive substances (TBARS). However, under the mercuric ions stress, the alfalfa plants showed no significant alteration of hydrogen peroxide in roots. Analysis of lipoxygenase activity by non-denaturing polyacrylamide gel electrophoresis (PAGE) showed that there were two isoforms in the root of alfalfa plants, but they showed quite different patterns under the Hg exposure. Also, using non-denaturing PAGE, activities of superoxide dismutase (SOD) and peroxidase (POD) were determined in roots after treatment with Hg ions. The total activities of SOD and POD increased in roots after Hg treatment of roots. Activity of ascorbate peroxides (APX) was stimulated at relatively high concentration of Hg (40microM), and after prolonged Hg exposure (20microM, 24h). In contrast, glutathione reductase activity was depressed at higher concentrations of Hg (10-20microM). Treatments of seedlings with 10-40microM Hg decreased the ascorbate and glutathione amounts but increased total non-protein thiols. The above results indicated that Hg exerted its toxic effect on the root growth of alfalfa by induction of oxidative stress.

Recovery of uptake and assimilation of nitrate in Scenedesmus sp. previously exposed to elevated levels of Cu2+ and Zn2+.

A study of the effects of elevated levels of Cu2+ and Zn2+ on NO3- uptake and nitrate reductase (NR) activity in Scenedesmus sp. was carried out. The two metals inhibited NR and NO3- uptake in a concentration-dependent manner, with the latter process being inhibited more strongly than the former. After withdrawal of metal stress, NR activity and NO3- uptake recovered in a metal ion concentration-dependent manner. Dark pretreatment of the alga enhanced the toxic effects of the metal ions on NR activity and NO3- uptake. The recovery from metal stress was slower in the dark-pretreated cells in comparison to the light-pretreated cells. No recovery of NR and NO3- uptake occurred in the presence of the photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), suggesting that photosynthesis was required for the recovery from metal stress. Cycloheximide blocked the recovery of NR activity in metal-treated alga, suggesting that new enzyme synthesis was required for the recovery from metal stress.