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.

Lignin, an active component in the corn silk water extract, inhibits glycation.

The formation of advanced glycation end products is associated with aging and diabetic complications such as neuropathy, retinopathy, and nephropathy. Thus, the suppression of AGEs formation could prevent and/or treat their related disorders. Corn silk is used as a traditional medicine for the prevention of diabetic complications and treatment of edema in Japan and China. Previous studies revealed the anti-glycation activity of flavonoids in the methanolic extract of corn silk. The anti-glycation activity of the corn silk water extract was higher than that of the methanolic extract; however, the active components of the water extract remained unidentified. The purpose of this study is to make clear the components showing anti-glycation activity in the corn silk water extract and elucidated their structural characteristics. The evaluation of anti-glycation activity was carried out by enzyme-linked immunosorbent assay to detect glycated bovine serum albumin. Remarkable anti-glycation activity was observed in the > 3 kDa fraction. Reversed-phase HPLC analysis of this fraction showed broad peaks characteristic of high-molecular-weight polyphenols. Decomposition reactions did not provide evidence of condensed or acid-hydrolyzable tannins. Therefore, polyphenols contained in the corn silk water extract were considered to be lignin-carbohydrate complex. The 1H- and 13C-nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy spectra of the > 3 kDa fraction were in agreement with the values reported for lignin. Consequently, we concluded that lignin-carbohydrate complex is one of the active components against glycation in the corn silk water extract.

Comparison of various commercially available cinnamon barks using NMR metabolomics and the quantification of coumarin by quantitative NMR methods.

Cinnamon bark is an important spice worldwide. In this study, the chemical diversity of various commercially available cinnamon barks that differed in their production areas and utility applications (culinary spice or medicines) were investigated by the use of 1H NMR metabolomics. Our results indicated that principle component analysis (PCA) and hierarchical cluster analysis (HCA) of the 1H NMR spectra of the cinnamon bark methanolic extracts including the deduction of their species by nucleotide sequence analysis enabled differentiation of the cinnamon barks according to their species, production areas and utility applications. The constituents of Vietnam cinnamon were found to differ significantly from the other samples investigated based on PCA score plots and HCA constellation dendrograms. Coumarin was found to be a key compound for the discrimination of Vietnamese cinnamon by multivariate analysis of the 1H NMR spectral data and direct comparison of the 1H NMR spectra. In addition, coumarin was quantified using quantitative NMR methods. As a result, coumarin was contained in Vietnamese cinnamon at a higher level compared to other cinnamons. This study indicated that 1H NMR metabolomics could deduce spices, utility, and producing area of commercially available cinnamon barks. Furthermore, combining quantitative 1H NMR methods with 1H NMR metabolomics enable quantification of coumarin in cinnamon bark on a single measurement.