ABSTRACT
To date, COVID-19 is still a severe threat to public health, hence specific effective therapeutic drugs development against SARS-CoV-2 is urgent needed. 3CLpro and PLpro and RdRp are the enzymes required for the SARS-CoV-2 RNA synthesis. Therefore, binding to the enzyme may interfere the enzyme function. Before, we found that sulfated polysaccharide binding to 3CLpro might block the virus replication. Hence, we hypothesize that negative charged pectin glycan may also impede the virus replication. Here we show that 922 crude polysaccharide from Syzygium aromaticum may near completely block SARS-CoV-2 replication. The inhibition rate was 99.9% (EC50 : 0.90 M). Interestingly, 922 can associates with 3CLpro, PLpro and RdRp. We further show that the homogeneous glycan 922211 from 922 may specifically attenuate 3CL protease activity. The IC50s of 922 and 922211 against 3CLpro are 4.73 {+/-} 1.05 {micro}M and 0.18 {+/-} 0.01 {micro}M, respectively. Monosaccharide composition analysis reveals that 922211 with molecular weight of 78.7 kDa is composed of rhamnose, galacturonic acid, galactose and arabinose in the molar ratio of 8.21 : 37.81 : 3.58 : 4.49. The structure characterization demonstrated that 922211 is a homogalacturonan linked to RG-I pectin polysaccharide. The linear homogalacturonan part in the backbone may be partly methyl esterified while RG-I type part bearing 1, 4-linked -GalpA, 1, 4-linked -GalpAOMe and 1, 2, 4-linked -Rhap. There are four branches attached to C-1 or C4 position of Rhamnose glycosyl residues on the backbone. The branches are composed of 1, 3-linked {beta}-Galp, terminal (T)-linked {beta}-Galp, 1, 5-linked -Araf, T-linked -Araf, 4-linked -GalpA and/or 4-linked {beta}-GalpA. The above results suggest that 922 and 922211 might be a potential novel leading compound for anti-SARS-CoV-2 new drug development.
ABSTRACT
Cordycepin (3'-deoxyadenosine) from Cordyceps militaris has been reported to have anti-tumor effects. However, the molecular target and mechanism underlying cordycepin impeding pancreatic cancer cell growth in vitro and in vivo remain vague. In this study, we reported functional target molecule of cordycepin which inhibited pancreatic cancer cells growth in vitro and in vivo. Cordycepin was confirmed to induce apoptosis by activating caspase-3, caspase-9 and cytochrome c. Further studies suggested that MAPK pathway was blocked by cordycepin via inhibiting the expression of Ras and the phosphorylation of Erk. Moreover, cordycepin caused S-phase arrest and DNA damage associated with activating Chk2 (checkpoint kinase 2) pathway and downregulating cyclin A2 and CDK2 phosphorylation. Very interestingly, we showed that cordycepin could bind to FGFR2 (K = 7.77 × 10) very potently to inhibit pancreatic cancer cells growth by blocking Ras/ErK pathway. These results suggest that cordycepin could potentially be a leading compound which targeted FGFR2 to inhibit pancreatic cells growth by inducing cell apoptosis and causing cell cycle arrest via blocking FGFR/Ras/ERK signaling for anti-pancreatic cancer new drug development.
