Phospholipid Scramblase 1 Localizes Proximal to Sphingomyelin Synthase Isoforms but Is Not Involved in Sphingomyelin Synthesis.

Ceramide (Cer) is synthesized de novo in the bilayer of the endoplasmic reticulum and transported to the cytosolic leaflet of the trans-Golgi apparatus for sphingomyelin (SM) synthesis. As the active site of SM synthase (SMS) is located on the luminal side of the Golgi membrane, Cer translocates to the lumen via transbilayer movement for SM synthesis. However, the mechanism of transbilayer movement is not fully understood. As the Cer-related translocases seem to localize near the SMS, the protein was identified using proximity-dependent biotin identification proteomics. Phospholipid scramblase 1 (PLSCR1), which is thought to act as a scramblase for phosphatidylserine and phosphatidylethanolamine, was identified as a protein proximal to the SMS isoforms SMS1 and SMS2. Although five isoforms of PLSCR have been reported in humans, only PLSCR1, PLSCR3, and PLSCR4 are expressed in HEK293T cells. Confocal microscopic analysis showed that PLSCR1 and PLSCR4 partially co-localized with p230, a trans-Golgi network marker, where SMS isoforms are localized. We established CRISPR/Cas9-mediated PLSCR1, PLSCR3, and PLSCR4 single-knockout cells and PLSCR1, 3, 4 triple knockout HEK293T cells. Liquid chromatography-tandem mass spectrometry revealed that the levels of species with distinct acyl chains in Cer and SM were not significantly different in single knockout cells or in the triple knockout cells compared to the wild-type cells. Our findings suggest that PLSCR1 is localized in the vicinity of SMS isoforms, however is not involved in the transbilayer movement of Cer for SM synthesis.

Ciclesonide Inhibits SARS-CoV-2 Papain-Like Protease in Vitro.

The emergence of coronavirus disease 2019 (COVID-19), a novel identified pneumonia resulting from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, has significantly impacted and posed significant challenges to human society. The papain-like protease (PLpro) found in the nonstructural protein 3 of SARS-CoV-2 plays a vital role in viral replication. Moreover, PLpro disrupts the host immune response by cleaving ubiquitin and interferon-stimulated gene 15 from host proteins. Consequently, PLpro has emerged as a promising drug target against SARS-CoV-2 infection. Computational studies have reported that ciclesonide can bind to SARS-CoV-2 PLpro. However, the inhibitory effects of ciclenoside on the PLpro have not been experimentally evaluated. Here, we evaluated the inhibitory effects of synthetic glucocorticoids (sGCs), including ciclesonide, on SARS-CoV-2 PLpro in vitro assay. Ciclesonide significantly inhibited the enzymatic activity of PLpro, compared with other sGCs and its IC50 was 18.4 ± 1.89 µM. These findings provide insights into the development of PLpro inhibitors.

Inhibitory effects of senkyuchachosan on SARS-CoV-2 papain-like protease activity in vitro.

Papain-like protease (PLpro) enzyme plays a vital role in viral replication as it breaks down polyproteins and disrupts the host's immune response. There are few reports on Kampo formulas that focus on PLpro activity. In this study, we evaluated the inhibitory effects of senkyuchachosan, a traditional Japanese medicine, on PLpro of SARS-CoV-2, the virus responsible for causing COVID-19. We purified the PLpro enzyme and conducted in vitro enzymatic assays using specific substrates. Among the nine crude drugs present in senkyuchachosan, four (Cyperi Rhizoma, Schizonepetae Spica, Menthae Herba, and Camelliae sinensis Folium [CsF]) strongly inhibited PLpro activity. CsF, derived from Camellia sinensis (green tea), contains polyphenols, including catechins and tannins. To confirm that the PLpro inhibitory effects of senkyuchachosan predominantly stem from tannins, the tannins were removed from the decoction using polyvinylpolypyrrolidone (PVPP). The inhibitory effect of senkyuchachosan on PLpro activity was reduced by the removal of PVPP. In addition, the tannin fraction obtained from the CsF extracts showed significant PLpro inhibitory effects. These findings lay the groundwork for the potential development of therapeutic agents that target SARS-CoV-2 infection by intervening in proteolytic cleavage of the virus.

Method for Preparing Recombinant Galectin-2 Protein without Escherichia coli-Specific Post-translational Modifications.

Galectin-2 (Gal-2) is an animal lectin with specificity for ß-galactosides. It is predominantly expressed and suggested to play a protective function in the gastrointestinal tract; therefore, it can be used as a protein drug. Recombinant proteins have been expressed using Escherichia coli and used to study the function of Gal-2. The recombinant human Gal-2 (hGal-2) protein purified via affinity chromatography after being expressed in E. coli was not completely homogeneous. Mass spectrometry confirmed that some recombinant Gal-2 were phosphogluconoylated. In contrast, the recombinant mouse Gal-2 (mGal-2) protein purified using affinity chromatography after being expressed in E. coli contained a different form of Gal-2 with a larger molecular weight. This was due to mistranslating the original mGal-2 stop codon TGA to tryptophan (TGG). In this report, to obtain a homogeneous Gal-2 protein for further studies, we attempted the following methods: for hGal-2, 1) replacement of the lysine (Lys) residues, which was easily phosphogluconoylated with arginine (Arg) residues, and 2) addition of histidine (His)-tag on the N-terminus of the recombinant protein and cleavage with protease after expression; for mGal-2, 3) changing the stop codon from TGA to TAA, which is commonly used in E. coli. We obtained an almost homogeneous recombinant Gal-2 protein (human and mouse). These results have important implications for using Gal-2 as a protein drug.

Inhibition of furin-like enzymatic activities and SARS-CoV-2 infection by osthole and phenolic compounds with aryl side chains.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), spread as a pandemic and caused damage to people's lives and countries' economies. The spike (S) protein of SARS-CoV-2 contains a cleavage motif, Arg-X-X-Arg, for furin and furin-like enzymes at the boundary of the S1/S2 subunits. Given that cleavage plays a crucial role in S protein activation and viral entry, the cleavage motif was selected as the target. Our previous fluorogenic substrate study showed that osthole, a coumarin compound, inhibits furin-like enzyme activity. In this study, we examined the potential activities of 15 compounds with a structure-activity relationship with osthole, and evaluated their protective ability against SARS-CoV-2 infection. Of the 15 compounds tested, compounds C1 and C2 exhibited the inhibitory effects of osthole against furin-like enzymatic activity; however, little or no inhibitory effects against furin activity were observed. We further examined the inhibition of SARS-CoV-2 activity by compounds C1 and C2 using a Vero E6 cell line that expresses the transmembrane protease serine 2 (TMPRSS2). Compounds C1, C2, and osthole effectively inhibited SARS-CoV-2 infection. Therefore, osthole and its derivatives can potentially be used as therapeutic agents against SARS-CoV-2.

Characterization of Carbohydrates, Amino Acids, Viscosity, and Antioxidant Capacity in Rice Wines Made in Saitama, Japan, with Different Sake Rice.

We investigated the physicochemical properties of Japanese rice wines, including their functional properties and carbohydrate and amino acid content in solution and solid state. Three samples were tested. The glucose, allose, and raffinose contents in samples (A, B, C) in g/100 g were (3.47, 3.45, 7.05), (1.60, 1.63, 1.61), and (2.14, 2.75, 1.49), respectively. The total amino acid in µmol/mL was (3.1, 3.5, 4.4). Glutamic acid, alanine, and arginine varied in content across the samples. The viscosity (10 °C) and activation energy (ΔE) calculated using the Andrade equation were (2.81 ± 0.03, 2.74 ± 0.06, 2.69 ± 0.03) mPa-s and (22.3 ± 1.1, 22.0 ± 0.2, 21.3 ± 0.5) kJ/mol, respectively. Principal component analysis using FT-IR spectra confirmed the separation of the samples into principal components 2 and 3. The IC50 values from the DPPH radical scavenging test were (2364.7 ± 185.3, 3041.9 ± 355.1, 3842.7 ± 228.1) µg/mL. Thus, the three rice wines had different carbohydrate and amino acid contents, viscosities, and antioxidant capacities.

Characterization, Preparation, and Promotion of Plant Growth of 1,3-Diphenylurea/ß-Cyclodextrin Derivatives Inclusion Complexes.

The study aimed to prepare inclusion complexes of 1,3-diphenylurea (DPU) with ß-cyclodextrin (ßCD) and 2-hydroxypropyl-ß-cyclodextrin (HP-ßCD) using a three-dimensional ground mixture (3DGM). Their physicochemical properties, intermolecular interactions, solubilities, and plant growth-promoting activities were investigated on broccoli sprouts. Phase-solubility diagrams indicated the stability constant (Ks) and complexation efficiency (CE) of ßCD/DPU were found to be K1/1 = 250 M-1, CE = 2.48× 10-3. The Ks and CEs of HP-ßCD/DPU were found to be K1/1 = 427 M-1, CE = 3.93 × 10-3 and K2/1 = 196 M-1, CE = 1.93 × 10-3 respectively. The powder X-ray diffraction results of 3DGM (ßCD/DPU = 2/1, HP-ßCD/DPU = 2/1) showed that the diffraction peaks originating from the DPU and ßCD disappeared, indicating a halo pattern. Differential scanning calorimetry results showed an endothermic peak at 244 °C derived from the melting point of DPU, but the endothermic peak disappeared in the 3DGM (ßCD/DPU = 2/1, HP-ßCD/DPU = 2/1). Near-infrared absorption spectra showed peak shifts in 3DGM (ßCD/DPU and HP-ßCD/DPU) at the -CH and -NH groups of DPU and the -OH groups of ßCDs and free water. In the dissolution test (after 5 min), the concentration of intact DPU was 0.083 µg/mL. However, the dissolution concentrations of DPU in the 3DGM (ßCD/DPU = 1/1), 3DGM (ßCD/DPU = 2/1), 3DGM (HP-ßCD/DPU = 1/1), and 3DGM (HP-ßCD/DPU = 2/1) were 3.27, 3.64, 5.70, and 7.03 µg/mL, respectively, indicating higher solubility than that of the intact DPU. Further, 1H-1H NOESY NMR spectroscopic measurements showed cross-peaks between H-A (7.32 ppm) and H-B (7.12 ppm) of DPU and H-6 (3.79 ppm) in the ßCD cavity of the 3DGM (ßCD/DPU = 2/1). A cross-peak was also observed among DPU H-A (7.32 ppm), H-B (7.11 ppm), and H-6 (3.78 ppm) in the ßCD cavity. The results of the broccoli sprout cultivation experiment showed that 3DGM (ßCD/DPU = 1/1), 3DGM (ßCD/DPU = 2/1), 3DGM (HP-ßCD/DPU = 1/1), and 3DGM (HP-ßCD/DPU = 2/1) increased the stem thickness compared with that of the control group (DPU). These results indicated that the ßCD/DPU and HP-ßCD/DPU inclusion complexes were formed by the three-dimensional mixing and milling method, which enhanced the solubility and plant growth-promoting effects.

Development of Novel Monoclonal Antibodies Against Nattokinase.

Nattokinase is a protease produced by Bacillus subtilis var. natto that exhibits various beneficial biological effects. Thus, a reliable assay to determine nattokinase levels is needed. In this study, we developed novel mouse monoclonal antibodies (mAbs) that recognize nattokinase, and created a specific and sensitive enzyme-linked immunosorbent assay (ELISA) to measure nattokinase levels. The ELISA was developed using a combination of new mouse antinattokinase mAbs used as capture antibodies coated onto 96-well plates, with a peroxidase-conjugated antibody used for detection. This ELISA enabled detection of nattokinase at 1 ng/mL. We believe that the novel mAbs developed in this study will be useful in future for elucidating nattokinase function.

Inhibitory effect of Ephedra herba on human norovirus infection in human intestinal organoids.

Human norovirus (HuNoV) is a major cause of acute gastroenteritis and foodborne diseases worldwide with public health concern, yet no antiviral therapies have been developed. In this study, we aimed to screen crude drugs, which are components of Japanese traditional medicine, ''Kampo'' to see their effects on HuNoV infection using a reproducible HuNoV cultivation system, stem-cell derived human intestinal organoids/enteroids (HIOs). Among the 22 crude drugs tested, Ephedra herba significantly inhibited HuNoV infection in HIOs. A time-of-drug addition experiment suggested that this crude drug more preferentially targets post-entry step than entry step for the inhibition. To our knowledge, this is the first anti-HuNoV inhibitor screen targeting crude drugs, and Ephedra herba was identified as a novel inhibitor candidate that merits further study.

Reactive oxygen species are associated with the inhibitory effect of N-(4-hydroxyphenyl)-retinamide on the entry of the severe acute respiratory syndrome-coronavirus 2.

N-(4-hydroxyphenyl)-retinamide (4-HPR) inhibits the dihydroceramide Δ4-desaturase 1 (DEGS1) enzymatic activity. We previously reported that 4-HPR suppresses the severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) spike protein-mediated membrane fusion through a decrease in membrane fluidity in a DEGS1-independent manner. However, the precise mechanism underlying the inhibition of viral entry by 4-HPR remains unclear. In this study, we examined the role of reactive oxygen species (ROS) in the inhibition of membrane fusion by 4-HPR because 4-HPR is a well-known ROS-inducing agent. Intracellular ROS generation was found to be increased in the target cells in a cell-cell fusion assay after 4-HPR treatment, which was attenuated by the addition of the antioxidant, α-tocopherol (TCP). The reduction in membrane fusion susceptibility by 4-HPR treatment in the cell-cell fusion assay was alleviated by TCP addition. Furthermore, fluorescence recovery after photobleaching analysis showed that the lateral diffusion of glycosylphosphatidylinositol-anchored protein and SARS CoV-2 receptor was reduced by 4-HPR treatment and restored by TCP addition. These results indicate that the decrease in SARS-CoV-2 spike protein-mediated membrane fusion and membrane fluidity by 4-HPR was due to ROS generation. Taken together, these results demonstrate that ROS production is associated with the 4-HPR inhibitory effect on SARS-CoV-2 entry.

Anti-inflammatory Effect of a Combination of Cannabidiol and Morinda citrifolia Extract on Lipopolysaccharide-stimulated RAW264 Macrophages.

BACKGROUND/AIM: The inflammatory response plays an important role in the activation and progression of many inflammation-related diseases. Cannabis sativa and Morinda citrifolia have long been used in folk medicine to treat inflammation. Cannabidiol is the most abundant non-psychoactive phytocannabinoid in C. sativa and exhibits anti-inflammatory activity. The objective of this study was to examine the anti-inflammatory effect of cannabidiol in combination with M. citrifolia and compare its effects with those of cannabidiol alone. MATERIALS AND METHODS: RAW264 cells stimulated with lipopolysaccharide (200 ng/ml) were treated with cannabidiol (0-10 µM), M. citrifolia seed extract (0-100 µg/ml), or a combination of both for 8 or 24 h. Following the treatments, nitric oxide production in the activated RAW264 cells and the expression of inducible nitric oxide synthase were assessed. RESULTS: Our results showed that combination of cannabidiol (2.5 µM) and M. citrifolia seed extract (100 µg/ml) exhibited more efficient inhibition of nitric oxide production than cannabidiol treatment alone in lipopolysaccharide-stimulated RAW264 cells. The combination treatment also reduced the expression of inducible nitric oxide synthase. CONCLUSION: These results suggest that the anti-inflammatory effect of combined treatment with cannabidiol and M. citrifolia seed extract causes a reduction in the expression of inflammatory mediators.

Effect of Maillard reaction on the quality of clarified butter, ghee.

In Ayurveda, a traditional Indian medicine system, clarified butter is called ghee and is used for food and medicinal purposes. Since butter is subjected to heat to prepare ghee, the heating process affects the ghee quality, such as oxidation, flavor, nutritional value, and biological activity. Therefore, this study focused on the Maillard reaction progress and free-radical scavenging activity with temperature and time during ghee preparation. First, ghee was prepared at low to high temperatures, and its quality (milk fat content, retinol, α-tocopherol, peroxide value, Maillard reaction progress, and free radical scavenging activity) was evaluated. Maillard reaction progress was enhanced at medium and high temperatures (120-160 â„ƒ), and the free radical-scavenging activity of ghee corresponded to the Maillard reaction progress. Since ghee is often reheated during use, we further evaluated the effect of the reheating process. The reheating process did not alter the Maillard reaction progress or the free radical scavenging activity. Our findings serve as good quality control measures for ghee preparation.

Dihydroceramide Δ4-Desaturase 1 Is Not Involved in SARS-CoV-2 Infection.

Dihydroceramide Δ4-desaturase 1 (DEGS1) enzymatic activity is inhibited with N-(4-hydroxyphenyl)-retinamide (4-HPR). We reported previously that 4-HPR suppresses severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry through a DEGS1-independent mechanism. However, it remains unclear whether DEGS1 is involved in other SARS-CoV-2 infection processes, such as virus replication and release. Here we established DEGS1 knockout (KO) in VeroE6TMPRSS2 cells. No significant difference was observed in virus production in the culture supernatant between wild-type (WT) cells and DEGS1-KO cells, although the levels of dihydroceramide (DHCer), a DEGS1 substrate, were significantly higher in DEGS1-KO cells than WT cells. Furthermore, the virus-induced cytopathic effect was also observed in DEGS1-KO cells. Importantly, the EC50 value of 4-HPR in DEGS1-KO cells was almost identical to the value reported previously in WT cells. Our results indicated the lack of involvement of DEGS1 in SARS-CoV-2 infection.

Degradative Effect of Nattokinase on Spike Protein of SARS-CoV-2.

The coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged as a pandemic and has inflicted enormous damage on the lives of the people and economy of many countries worldwide. However, therapeutic agents against SARS-CoV-2 remain unclear. SARS-CoV-2 has a spike protein (S protein), and cleavage of the S protein is essential for viral entry. Nattokinase is produced by Bacillus subtilis var. natto and is beneficial to human health. In this study, we examined the effect of nattokinase on the S protein of SARS-CoV-2. When cell lysates transfected with S protein were incubated with nattokinase, the S protein was degraded in a dose- and time-dependent manner. Immunofluorescence analysis showed that S protein on the cell surface was degraded when nattokinase was added to the culture medium. Thus, our findings suggest that nattokinase exhibits potential for the inhibition of SARS-CoV-2 infection via S protein degradation.

Preparation, Characterization, and In Vitro Evaluation of Inclusion Complexes Formed between S-Allylcysteine and Cyclodextrins.

The present study prepared inclusion complexes of S-allylcysteine (SAC) and cyclodextrin (α, ß, γ) by the freeze-drying (FD) method and verified the inclusion behavior of the solid dispersion. Also, the study investigated the effect of SAC/CD complex formation on liver tumor cells. Isothermal titration calorimetry (ITC) measurements confirmed the exothermic titration curve for SAC/αCD, suggesting a molar ratio of SAC/αCD = 1/1, but no exothermic/endothermic reaction was obtained for the SAC/ßCD and SAC/γCD system. Powder X-ray diffraction (PXRD) results showed that the characteristic diffraction peaks of SAC and CDs disappeared in FD (SAC/αCD) and FD (SAC/γCD), indicated by a halo pattern. On the other hand, diffraction peaks originating from SAC and ßCDs were observed in FD (SAC/ßCD). Near-infrared (NIR) absorption spectroscopy results showed that CH and OH groups derived from SAC and OH groups derived from αCD and γCD cavity were shifted, suggesting complex formation due to intermolecular interactions occurring in SAC/αCD and SAC/γCD. Stability test results showed that the stability was maintained with FD (SAC/αCD) over FD (SAC/ßCD) and FD (SAC/γCD). In 1H-1H of NOESY NMR measurement, FD (SAC/αCD) was confirmed to have a cross peak at the CH group of the alkene of SAC and the proton (H-3, -5, -6) in the αCD cavity. In FD (SAC/γCD), a cross peak was confirmed at the alkyl group on the carbonyl group side of SAC and the proton (H-3) in the cavity of γCD. From the above, it was suggested that the inclusion mode of SAC is different on FD (SAC/CDs). The results of the hepatocyte proliferation inhibition test using HepG2 cells showed that FD (SAC/ßCD) inhibited cell proliferation. On the other hand, FD (SAC/αCD) and FD (SAC/γCD) did not show a significant decrease in the number of viable cells. These results suggest that the difference in the inclusion mode may contribute to the stability and cell proliferation inhibition.

Lysophosphatidylinositol Induced Morphological Changes and Stress Fiber Formation through the GPR55-RhoA-ROCK Pathway.

We previously reported that lysophosphatidylinositol (LPI) functions as an endogenous agonist of GPR55, a novel cannabinoid receptor. However, the physiological roles of LPI-GPR55 have not yet been elucidated in detail. In the present study, we found that LPI induced morphological changes in GPR55-expressing HEK293 cells. LPI induced the cell rounding of GPR55-expressing HEK293 cells but not of empty-vector-transfected cells. LPI also induced the activation of small GTP-binding protein RhoA and increased stress fiber formation in GPR55-expressing HEK293 cells. The inhibition of RhoA and Rho kinase ROCK by the C3 exoenzyme and the ROCK inhibitor reduced LPI-induced cell rounding and stress fiber formation. These results clearly indicated that the LPI-induced morphological changes and the assembly of the cytoskeletons were mediated through the GPR55-RhoA-ROCK pathway.

Preparation, Characterization, Solubility, and Antioxidant Capacity of Ellagic Acid-Urea Complex.

Ellagic acid (EA), a natural polyphenol found in berries, has high antioxidant capacity. This study aimed to improve EA solubility by complex formation with urea (UR) using solvent evaporation method and evaluate its solubility, antioxidant capacity, and physical properties. The solubility test (25 °C, 72 h) showed that the solubility of EVP (EA/UR = 1/1) was approximately two-fold higher than that of EA (7.13 µg/mL versus 3.99 µg/mL). Moreover, the IC50 values of EA and EVP (EA/UR = 1/1) (1.50 µg/mL and 1.30 µg/mL, respectively) showed higher antioxidant capacity of EVP than that of EA. DSC analysis revealed that the UR peak at 134 °C disappeared, and a new endothermic peak was observed at approximately 250 °C for EVP (EA/UR = 1/1). PXRD measurements showed that the characteristic peaks of EA at 2θ = 12.0° and 28.0° and of UR at 2θ = 22.0°, 24.3°, and 29.1° disappeared and that new peaks were identified at 2θ = 10.6°, 18.7°, and 26.8° for EVP (EA/UR = 1/1). According to 2D NOESY NMR spectroscopy, cross-peaks were observed between the -NH and -OH groups, suggesting intermolecular interactions between EA and UR. Therefore, complexation was confirmed in EA/UR = 1/1 prepared by solvent evaporation, suggesting that it contributed to the improvement in solubility and antioxidant capacity of EA.

Curcumae Longae Rhizoma and Saussureae Radix Inhibit Nitric Oxide Production and Cannabinoid Receptor 2 Down-regulation.

BACKGROUND/AIM: The cannabinoid 2 (CB2) receptor is an important regulator of immunoinflammatory responses. Crude drugs commonly used in Japanese traditional Kampo medicine have displayed anti-inflammatory effects; however, few studies have reported that these effects are mediated via CB2 receptor signaling. Therefore, this study aimed to elucidate CB2 receptor-related anti-inflammatory regulation in crude drugs. MATERIALS AND METHODS: The ethanol extracts of 34 crude drugs listed in the Japanese Pharmacopeia were tested, and the inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production were evaluated in murine macrophage RAW 264 cells. RESULTS: The extracts of Curcumae Longae Rhizoma (dried rhizome of Curcuma longa) and Saussureae Radix (dried root of Saussurea lappa) significantly inhibited NO production and attenuated the LPS-induced decrease in CB2 receptor mRNA expression. CONCLUSION: Curcumae Longae Rhizoma and Saussureae Radix can modulate the CB2-receptor-related anti-inflammatory regulation in macrophages.

Inhibitory effect of honokiol on furin-like activity and SARS-CoV-2 infection.

The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as a pandemic and has caused damage to the lives of the people and economy of countries. However, the therapeutic reagents against SARS-CoV-2 remain unclear. The spike (S) protein of SARS-CoV-2 contains a cleavage motif at the S1/S2 boundary, known to be cleaved by furin. As cleavage is essential for S protein activation and viral entry, furin was selected as the target compound. In this study, we examined the inhibitory effects of two lignans (honokiol and magnolol) on furin-like enzymatic activity using a fluorogenic substrate with whole-cell lysates. Of two compounds tested, honokiol partially inhibited furin-like enzymatic activity. We further examined the anti-SARS-CoV-2 activity of honokiol using VeroE6 cell line, which is stably expressing a transmembrane protease serine 2 (TMPRSS2). It was shown that honokiol exhibited remarkable inhibition of SARS-CoV-2 infection. Therefore, honokiol and crude drugs which contain honokiol such as Magnolia species have a potential therapeutic reagents for SARS-CoV-2.

Preparation and Characterization of a Hybrid Complex of Cyclodextrin-Based Metal-Organic Frameworks-1 and Ascorbic Acid Derivatives.

Cyclodextrin-based metal-organic frameworks-1 (CD-MOF-1) prepared using potassium hydroxide, ethanol, and γ-cyclodextrin (γ-CD) has been reported as a new type of MOF for the development of pharmaceutical formulations. The present study aimed to investigate the physicochemical properties of ascorbic acid derivatives (L-ascorbyl 6-palmitate (ASCP); L-ascorbyl 2,6-palmitate (ASCDP)) complexed with CD-MOF-1 by a solvent evaporation method. Powder X-ray diffraction revealed that the crystal diffraction pattern of CD-MOF-1 changed from α-type to ß-type when prepared by a solvent evaporation method. For ASCP/CD-MOF-1 = 1/2 and ASCDP/CD-MOF-1 = 1/4 evaporated samples, the crystal diffraction peaks derived from ASCP and ASCDP disappeared, indicating a ß-like behavior. Differential scanning calorimetry results revealed that the endothermic peaks of evaporated samples (ASCP/CD-MOF-1 = 1/2 and ASCDP/CD-MOF-1 = 1/4) were not detected due to melting. Furthermore, intermolecular interactions were observed in the hydrogen bonds between the CH groups of the side chains of ASCP and ASCDP and the OH group of CD-MOF-1 in (ASCP/CD-MOF-1 = 1/2) and EVP (ASCDP/CD-MOF-1 = 1/4), based on the near-infrared absorption spectroscopy analysis. CD-MOF-1 did not form inclusion complexes with the lactone rings of ASCP and ASCDP, but with the lipophilic side chains. These results suggested that CD-MOF-1 may be useful in preparing novel drug carriers for ASCP and ASCDP.