Inhibition of SARS-CoV-2 Virus Entry by the Crude Polysaccharides of Seaweeds and Abalone Viscera In Vitro

Much attention is being devoted to the potential of marine sulfated polysaccharides as antiviral agents in preventing COVID-19. In this study, sulfated fucoidan and crude polysaccharides, extracted from six seaweed species (Undaria pinnatifida sporophyll, Laminaria japonica, Hizikia fusiforme, Sargassum horneri, Codium fragile, Porphyra tenera) and Haliotis discus hannai (abalone viscera), were screened for their inhibitory activity against SARS-CoV-2 virus entry. Most of them showed significant antiviral activities at an IC50 of 12~289 μg/mL against SARS-CoV-2 pseudovirus in HEK293/ACE2, except for P. tenera (IC50 > 1000 μg/mL). The crude polysaccharide of S. horneri showed the strongest antiviral activity, with an IC50 of 12 μg/mL, to prevent COVID-19 entry, and abalone viscera and H. fusiforme could also inhibit SARS-CoV-2 infection with an IC50 of 33 μg/mL and 47 μg/mL, respectively. The common properties of these crude polysaccharides, which have strong antiviral activity, are high molecular weight (>800 kDa), high total carbohydrate (62.7~99.1%), high fucose content (37.3~66.2%), and highly branched polysaccharides. These results indicated that the crude polysaccharides from seaweeds and abalone viscera can effectively inhibit SARS-CoV-2 entry.

Inhibitory Effects of Porphyra tenera Extract on Oxidation and Inflammatory Responses

Porphyra tenera (laver) has long been a popular and traditional seaweed food in Korea, Japan, and China. Historically, it was known as a marine medicinal herb to treat hemorrhoids and cholera morbus in Donguibogam. We investigated the effects of P. tenera extract (PTE) for its antioxidant and anti-inflammatory activities. These activities were measured using assays for 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) radical scavenging and its superoxide dismutase- (SOD-) like activity, and through the inhibitory production of inflammatory mediators (prostaglandin E2 (PGE2), NO, tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6)) in lipopolysaccharide- (LPS-) stimulated Raw 264.7 cells. The antioxidant assay results showed that PTE displayed DPPH radical scavenging activity (46.44%), NO radical scavenging activity (67.14%), and SOD-like activity (80.29%) at a concentration of 5 mg/mL. In the anti-inflammatory assays, treatment with PTE (1 mg/mL) significantly inhibited expression levels of LPS-induced COX-2 and iNOS, as well as the production of PGE2, NO, TNF-α, and IL-6. These results show that PTE has antioxidant and anti-inflammatory properties and provide scientific evidence to explain the antioxidative and anti-inflammatory properties of PTE.

Anti-Inflammatory Properties and Gut Microbiota Modulation of Porphyra tenera Extracts in Dextran Sodium Sulfate-Induced Colitis in Mice

Porphyra tenera (PT) is a functional seaweed food that has been reported for health benefits such as antioxidant, immunostimulant, anti-inflammation, and hepatoprotective effects. In this study, we investigated the effect of PT extracts on gut microbiota modulation in colitis-induced mice. The mice experiment was designed as three groups including normal mice (CTL), dextran sodium sulfate (DSS)-fed mice, and DSS plus PT extracts-fed mice (PTE). DSS was administrated through drinking water containing DSS for 1 week, and the PT extract was ingested into the gastrointestinal tract in mice. PT extract ameliorated the decreased body weight and colon length and improved disease activity index and pro-inflammatory cytokine expression. In addition, PT extract significantly shifted the gut microbiota of mice. DSS treatment significantly increased the portion of harmful bacteria (i.e., Helicobacter, Mucipirillum, and Parasutterella) and decreased the butyrate producing bacteria (i.e., Acetatifactor, Alistipes, Oscillibacter, and Clostridium_XIVb). PT extract increased the abundance of genera Clostridium_XIVb and also enriched some of predicted metabolic activities such as glyoxylate cycle, ethylmalonyl-CoA pathway, nitrate reduction, creatinine degradation, and glycine betaine metabolism. These results suggest that PT extract may ameliorate the DSS-induced colitis inflammation through regulating the compositions and functions of gut microbiota in mice.

The Efficiency of Atmospheric Dielectric Barrier Discharge Plasma against Escherichia coli and Bacillus cereus on Dried Laver (Porphyra tenera)

This study investigated the effects of atmospheric dielectric barrier discharge (DBD) plasma (1.1 kV, 43 kHz, 5–30 min, N2: 1.5 L/m) on the reduction of Escherichia coli and Bacillus cereus on dried laver. The reductions of E. coli and B. cereus by 5, 10, 20, and 30 min of DBD plasma were 0.56 and 0.24, 0.61 and 0.66, 0.76 and 1.24, and 1.02 and 1.38 log CFU/g, respectively. The D-value of E. coli and B. cereus was predicted as 29.80 and 20.53 min, respectively, using the Weibull model for E. coli (R2 = 0.95) and first-order kinetics for B. cereus (R2 = 0.94). After DBD plasma 5–30 min treatment, there was no change in pH (6.20–6.21) and this value was higher than the untreated dried laver (6.08). All sensory scores in DBD plasma-treated laver were determined as >6 points. The 30 min of DBD plasma is regarded as a novel intervention for the control of potential hazardous bacteria in dried laver.

Effects of Porphyra tenera Supplementation on the Immune System: A Randomized, Double-Blind, and Placebo-Controlled Clinical Trial

Objective: The purpose of this study was to determine if Porphyra tenera extract (PTE) has immune-enhancing effects and is safe in healthy adults. Methods: Subjects who met the inclusion criteria (3 × 103 ≤ peripheral blood leukocyte level ≥ 8 × 103 cells/µL) were recruited for this study. Enrolled subjects (n = 120) were randomly assigned to either the PTE group (n = 60) and were given 2.5 g/day of PTE (as PTE) in capsule form or the placebo group (n = 60) and were given crystal cellulose capsules with the identical appearance, weight, and flavor as the PTE capsules for 8 weeks. Outcomes were assessed based on measuring natural killer (NK) cell activity, cytokines level, and upper respiratory infection (URI), and safety parameters were assessed at baseline and 8 weeks. Results: Compared with baseline, NK cell activity (%) increased for all effector cell-to-target cell ratios in the PTE group after 8 weeks; however, changes were not observed in the placebo group (p < 0.10). Subgroup analysis of 101 subjects without URI showed that NK cell activity in the PTE group tended to increase for all effector cell/target cell (E:T) ratios (E:T = 12.5:1 p = 0.068; E:T = 25:1 p = 0.036; E:T = 50:1 p = 0.081) compared with the placebo group. A significant difference between the two groups was observed for the E:T = 25:1 ratio, which increased from 20.3 ± 12.0% at baseline to 23.2 ± 12.4% after 8 weeks in the PTE group (p = 0.036). A significant difference was not observed in cytokine between the two groups. Conclusion: PTE supplementation appears to enhance immune function by improving NK cell activity without adverse effects in healthy adults.

Effects of Porphyra tenera Supplementation on the Immune System: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Objective: The purpose of this study was to determine if Porphyra tenera extract (PTE) has immune-enhancing effects and is safe in healthy adults. Methods: Subjects (3x103 &le; peripheral blood leukocyte levels &lt; 8x103 cells/&mu;l) who met the inclusion criteria were recruited for this study. Enrolled subjects (n=120) were randomly assigned to either the PTE group (n=60) who were given 2.5 g/day of PTE (as Porphyra tenera extract) in capsule form or the placebo group (n=60) who were given crystal cellulose capsules with the identical appearance, weight, and flavor as the PTE capsules for 8 weeks. Outcomes were assessed by measuring natural killer cell (NK-cell) activity, cytokines, and upper respiratory infection (URI), and safety parameters were assessed at baseline and 8 weeks. Results: Compared to baseline, NK cell activity (%) increased for all effector cell to target cell ratios in the PTE group after 8 weeks, but there were no changes in the placebo group (p&lt;0.1). Subgroup analysis of 101 subjects without an URI revealed that NK-cell activity in the PTE group tended to be increased for all E:T ratios (E:T=12.5:1 p=0.068; E:T=25:1 p=0.036; E:T=50:1 p=0.081) compared to the placebo group. There was a significant difference between these two groups for the E:T=25:1 ratio, which increased from 20.3&plusmn;12.0% at baseline to 23.2&plusmn;12.4% after 8 weeks in the PTE group (p=0.036). There was no significant difference in levels of cytokines between these two groups. Conclusions: PTE supplementation appears to enhance immune function by improving NK-cell activity without adverse effects in healthy adults.