Inhibitory Activity of Natural cis-Khellactone on Soluble Epoxide Hydrolase and Proinflammatory Cytokine Production in Lipopolysaccharides-Stimulated RAW264.7 Cells.

The pursuit of anti-inflammatory agents has led to intensive research on the inhibition of soluble epoxide hydrolase (sEH) and cytokine production using medicinal plants. In this study, we evaluated the efficacy of cis-khellactone, a compound isolated for the first time from the roots of Peucedanum japonicum. The compound was found to be a competitive inhibitor of sEH, exhibiting an IC50 value of 3.1 ± 2.5 µM and ki value of 3.5 µM. Molecular docking and dynamics simulations illustrated the binding pose of (-)cis-khellactone within the active site of sEH. The results suggest that binding of the inhibitor to the enzyme is largely dependent on the Trp336-Gln384 loop within the active site. Further, cis-khellactone was found to inhibit pro-inflammatory cytokines, including NO, iNOS, IL-1ß, and IL-4. These findings affirm that cis-khellactone could serve as a natural therapeutic candidate for the treatment of inflammation.

Inhibitory activity of lignanamides isolated from hemp seed hulls(Cannabis sativa L.) against soluble epoxide hydrolase.

Soluble epoxide hydrolase (sEH) is a therapeutic target for inflammation. In the present study, we isolated one new (1) and four known (2-5) compounds from the ethyl acetate fraction of hemp seed hulls. Their structures were elucidated as lignanamides via nuclear magnetic resonance and mass spectral analyses. All five compounds inhibited sEH activity, with half-maximal inhibitory concentrations of 2.7 ± 0.3 to 18.3 ± 1.0 µM. These lignanamides showed a competitive mechanism of inhibition via binding to sEH, with ki values below 10 µmol. Molecular simulations revealed that compounds 1-5 fit stably into the active site of sEH, and the key amino acid residues participating in their bonds were identified. It was confirmed that the potential inhibitors 4 and 5 continuously maintained a distance of 3.5 Å from one (Tyr383) and four amino (Asp335, Tyr383, Asn472, tyr516) residues, respectively. These findings provide a framework for the development of naturally derived sEH inhibitors.

Inhibition by components of Glycyrrhiza uralensis of 3CLpro and HCoV-OC43 proliferation.

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). 3CLpro is a key enzyme in coronavirus proliferation and a treatment target for COVID-19. In vitro and in silico, compounds 1-3 from Glycyrrhiza uralensis had inhibitory activity and binding affinity for 3CLpro. These compounds decreased HCoV-OC43 cytotoxicity in RD cells. Moreover, they inhibited viral growth by reducing the amounts of the necessary proteins (M, N, and RDRP). Therefore, compounds 1-3 are inhibitors of 3CLpro and HCoV-OC43 proliferation.

Inhibition of Soluble Epoxide Hydrolase Activity by Components of Glycyrrhiza uralensis.

Soluble epoxide hydrolase (sEH) is a target enzyme for the treatment of inflammation and cardiovascular disease. A Glycyrrhiza uralensis extract exhibited ~50% inhibition of sEH at 100 µg/mL, and column chromatography yielded compounds 1-11. Inhibitors 1, 4-6, 9, and 11 were non-competitive; inhibitors 3, 7, 8, and 10 were competitive. The IC50 value of inhibitor 10 was below 2 µM. Molecular simulation was used to identify the sEH binding site. Glycycoumarin (10) requires further evaluation in cells and animals.

Inhibitory Activity of 4-O-Benzoyl-3'-O-(OMethylsinapoyl) Sucrose from Polygala tenuifolia on Escherichia coliß-Glucuronidase.

Bacterial ß-glucuronidase in the intestine is involved in the conversion of 7-ethyl-10- hydroxycamptochecin glucuronide (derived from irinotecan) to 7-ethyl-10-hydroxycamptothecin, which causes intestinal bleeding and diarrhea (side effects of anti-cancer drugs). Twelve compounds (1-12) from Polygala tenuifolia were evaluated in terms of ß-glucuronidase inhibition in vitro. 4-O-Benzoyl-3'-O-(O-methylsinapoyl) sucrose (C3) was highly inhibitory at low concentrations. C3 (an uncompetitive inhibitor) exhibited a ki value of 13.4 µM; inhibitory activity increased as the substrate concentration rose. Molecular simulation revealed that C3 bound principally to the Gln158-Tyr160 enzyme loop. Thus, C3 will serve as a lead compound for development of new ß- glucuronidase inhibitors.

QTL Mapping for Gummy Stem Blight Resistance in Watermelon (Citrullus spp.).

Watermelon (Citrulluslanatus) is an economically important fruit crop worldwide. Gummy stem blight (GSB) is one of the most damaging diseases encountered during watermelon cultivation. In the present study, we identified quantitative trait loci (QTLs) associated with GSB resistance in an F2 population derived from a cross between maternal-susceptible line '920533' (C. lanatus) and the paternal-resistant line 'PI 189225' (C. amarus). The resistance of 178 F2 plants was assessed by two different evaluation methods, including leaf lesion (LL) and stem blight (SB). To analyze the QTLs associated with GSB resistance, a linkage map was constructed covering a total genetic distance of 1070.2 cM. QTL analysis detected three QTLs associated with GSB resistance on chromosome 8 and 6. Among them, two QTLs, qLL8.1 and qSB8.1 on chromosome 8 identified as major QTLs, explaining 10.5 and 10.0% of the phenotypic variations localizing at same area and sharing the same top markers for both LL and SB traits, respectively. A minor QTL, qSB6.1, explains 9.7% of phenotypic variations detected on chromosome 6 only for the SB trait. High-throughput markers were developed and validated for the selection of resistant QTLs using watermelon accessions, and commercial cultivars. Four potential candidate genes were predicted associated with GSB resistance based on the physical location of flanking markers on chromosome 8. These findings will be helpful for the development of watermelon cultivars resistant to GSB.

Cloning of genes differentially expressed during the initial stage of fruit development in melon (Cucumis melo cv. Reticulatus).

We have cloned genes involved in the initial stage of fruit development in the melon by suppression subtractive hybridization. A cDNA library of unfertilized ovules was subtracted from that of fruit 9 days after pollination (DAP); 10 of the 40 selected cDNA clones were identified by reverse Northern analysis as genes differentially expressed in fruit at 9 DAP. Seven of the ten genes were homologous to genes of known function; two were related to genes with unknown functions, and one was novel. With the exception of cucumisin, none of the cDNAs had been previously identified in melon. According to Northern analyses, six of the genes were expressed at high levels early in fruit development. Expression of cucumisin, Cmf-25, Cmf-30, and Cmf-124 was highest at 9 DAP, implying that these genes are involved in the initial stage of fruit development. Cmf-30, a seed nucellus-specific gene, was also expressed early in seed development. The other genes were expressed at a moderate level throughout fruit development, with the highest expression occurring in fruit at 9 and 18 DAP. In conclusion, nine new genes involved in early fruit development in melon were cloned, and their temporal and spatial expression patterns indicate that they are preferentially expressed during the active growing stage of fruit.