The spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contains a cleavage motif R-X-X-R for furin-like enzymes at the boundary of the S1/S2 subunits. The cleavage of the site by cellular proteases is essential for S protein activation and virus entry. We screened the inhibitory effects of crude drugs on in vitro furin-like enzymatic activities using a fluorogenic substrate with whole-cell lysates. Of the 124 crude drugs listed in the Japanese Pharmacopeia, aqueous ethanolic extract of Cnidii Monnieris Fructus, which is the dried fruit of Cnidium monnieri Cussion, significantly inhibited the furin-like enzymatic activities. We further fractionated the plant extract and isolated the two active compounds with the inhibitory activity, namely, imperatorin and osthole, whose IC₅₀ values were 1.45 mM and 9.45 µM, respectively. Our results indicated that Cnidii Monnieris Fructus might exert inhibitory effects on furin-like enzymatic activities, and that imperatorin and osthole of the crude drug could be potential inhibitors of the motif cleavage.

严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 的刺突 (S) 蛋白在 S1/S2 亚基的边界处含有弗林蛋白酶样酶的切割基序 RXXR。细胞蛋白酶对该位点的切割对于 S 蛋白激活和病毒进入是必不可少的。我们使用具有全细胞裂解物的荧光底物筛选了生药对体外弗林蛋白酶样酶活性的抑制作用。日本药典收录的124种生药中，蛇床子干果蛇床子的水乙醇提取物对弗林蛋白酶样活性有显着抑制作用。我们进一步分离植物提取物并分离出两种具有抑制活性的活性化合物，即欧前胡素和蛇床子素，其 IC_{50 个}值分别为 1.45 mM 和 9.45 μM。我们的研究结果表明，蛇床子可能对弗林蛋白酶样酶活性产生抑制作用，并且原料药中欧前胡素和蛇床子素可能是基序切割的潜在抑制剂。