A Comprehensive Review of Natural Flavonoids with Anti-SARS-CoV-2 Activity.

The COVID-19 pandemic caused by SARS-CoV-2 has majorly impacted public health and economies worldwide. Although several effective vaccines and drugs are now used to prevent and treat COVID-19, natural products, especially flavonoids, showed great therapeutic potential early in the pandemic and thus attracted particular attention. Quercetin, baicalein, baicalin, EGCG (epigallocatechin gallate), and luteolin are among the most studied flavonoids in this field. Flavonoids can directly or indirectly exert antiviral activities, such as the inhibition of virus invasion and the replication and inhibition of viral proteases. In addition, flavonoids can modulate the levels of interferon and proinflammatory factors. We have reviewed the previously reported relevant literature researching the pharmacological anti-SARS-CoV-2 activity of flavonoids where structures, classifications, synthetic pathways, and pharmacological effects are summarized. There is no doubt that flavonoids have great potential in the treatment of COVID-19. However, most of the current research is still in the theoretical stage. More studies are recommended to evaluate the efficacy and safety of flavonoids against SARS-CoV-2.

Impacts of Ag and Ag2S nanoparticles on the nitrogen removal within vertical flow constructed wetlands treating secondary effluent.

In this study, the effects of silver (Ag NPs) and sliver sulfide nanoparticles (Ag2S NPs) on nitrogen removal and nitrogen functional microbes in constructed wetlands were investigated. The obtained results demonstrated that inhibition extent on nitrogen removal relied on NPs types and high concentrations NPs showed higher negative effects. 0.5 mg/L Ag NPs had no influence on NH4+-N removal, amoA and nxrA gene copies, whereas Ag2S NPs and Ag+ decreased NH4+-N removal by reducing abundances of nitrifying genes. The concentrations of NO3--N and TN in all 0.5 mg/L obviously increased compared with control, resulting from decreasing functional genes and denitrifying bacteria. And 0.5 mg/L Ag NPs exhibited largest inhibitory effects, with the highest NO3--N effluent concentrations. 2 mg/L Ag NPs decreased NH4+-N removal, but adverse effects gradually vanished with extension of time, whereas both Ag2S NPs and Ag+ at 2 mg/L influenced NH4+-N transformation and decreased the abundance of amoA and nxrA genes and the AOB Nitrosomonas in CWs. Moreover, 2 mg/L of Ag NPs reduced NO3--N removal by decreasing abundance of nirS and key denitrifying bacteria. To sum up, the inhibition mechanisms concluded from current results were possibly in that Ag NPs exhibited nanotoxicity rather than ionic toxicity.

Comparative analysis of upward and downward vertical flow constructed wetlands on the nitrogen removal and functional microbes treating wastewater containing Ag nanoparticles.

This study investigated impacts of silver nanoparticles (AgNPs) on nitrogen removal within constructed wetlands (CWs) with different flow directions. The obtained results showed that addition of AgNPs at 0.5 and 2 mg/L significantly inhibited NH4+-N removal, resulting from lower abundances of functional genes (amoA and nxrA) within CWs. And higher abundances of amoA and nxrA genes at 0.5 mg/L were observed in downward flow CW, leading to better NH4+-N removal, compared to upward flow CW. Besides, nitrifying genes amoA and nxrA in upward flow CW at 2.0 mg/L exhibited higher than downward flow CW, explaining better NH4+-N removal in upward flow CW. 0.5 mg/L AgNPs significantly declined NO3--N and TN removal, resulted from decreasing abundances of nirK, nirS and nosZ. In contrast, abundances of nirK, nirS and nosZ genes had slightly lower or higher than before adding AgNPs in upward flow CW, leading to lower NO3--N and TN effluent concentrations. High throughput sequencing also indicated the changes of functional bacterial community after exposing to AgNPs.

[Cuscuta chinensis flavonoids reduce the expression of GM-CSF in the testis of oligozoospermia rats].

OBJECTIVE: To investigate the effect of Cuscuta chinensis flavonoids (CCF) on the expression of the granulocyte-macrophage colony-stimulating factor (GM-CSF) in the testis of the rat with oligozoospermia (OZ). METHODS: Thirty SD male rats were randomly divided into three groups of equal number, blank control, OZ model control and CCF intervention. The OZ model was established in the latter two groups by intraperitoneal injection of cyclophosphamide at 30 mg/kg qd for 5 successive days. From the 6th day, the rats in the CCF intervention group were treated intragastrically with mixed suspension of CCF at 5 mL/kg and those in the other two groups with normal saline, all for 4 weeks. The epididymal sperm concentration and motility and the testicular morphology were examined and the expression of GM-CSF in the testis tissue detected with the SELDI Protein Chip. RESULTS: Compared with the rats in the blank control and CCF intervention groups, the OZ model controls showed dramatically decreased epididymal sperm concentration and motility (both P < 0.01) and significant morphological changes in the testis with deformed seminiferous tubules and reduced number and disordered arrangement of spermatogenic cells. Normal testicular morphology was observed in the CCF intervention group and there were no statistically significant differences in sperm concentration and motility between the CCF intervention and blank control groups (P > 0.05). The expression of GM-CSF was significantly up-regulated in the testis tissue of the OZ model controls but lower than the minimum value obtained with the SELDI Protein Chip in the blank control and CCF intervention groups. CONCLUSIONS: Cuscuta chinensis flavonoids can significantly down-regulate the expression of GM-CSF in the testis of the rats with cyclophosphamide-induced oligozoospermia.

Long-term effects of environmentally relevant concentration of Ag nanoparticles on the pollutant removal and spatial distribution of silver in constructed wetlands with Cyperus alternifolius and Arundo donax.

The widely usage of silver nanoparticles in a range of consumer products inevitably results in its being released to the wastewater. As a result, the potential negative effects associated with AgNPs on wastewater treatment systems need to be assessed to develop the regulatory guidelines. In this paper, the exposure experiment at environmentally relevant concentration (100 µg L-1) were conducted to demonstrate the effects of AgNPs on the pollutant removals in constructed wetlands (CWs) with different plants and the spatial distribution of silver. Before adding AgNPs, the system with Arundo donax (VF2) had the better nitrogen removal than Cyperus alternifolius (VF1). After exposure for about 94 d, the average removal efficiencies of NH4+-N significantly reduced by 32.43% and 23.92%, TN of 15.82% and 17.18% and TP of 22.74% and 20.46% in VF1 and VF2, respectively, while the COD removal had no difference. However, presence of 100 µg L-1 AgNPs for about 450 d showed no inhibition effects on nutrient removals in two experimental CWs. Two wetlands showed high removal efficiencies of about 98% on AgNPs, indicating CWs could play a crucial role to control the AgNPs release to environment. It was found that AgNPs mainly accumulated in the soil layer with the Ag content of 0.45-5.96 µg g-1 dry weight in lower soil and 2.84-11.37 µg g-1 dry weight in upper soil. The roots of Cyperus alternifolius absorbed more AgNPs, with higher bioconcentration factors (1.32-1.44) than that of 0.59 in Arundo donax. The differences of translocation factors on leaves and stems in two test plants showed that AgNPs assimilated by roots in Cyperus alternifolius were more easily transferred to the leaves. The obtained results showed that the macrophyte Cyperus alternifolius could be better choice for immobilization of AgNPs.