Definition: In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
Input: Quinone-methide triterpenes, celastrol (1), pristimerin (2), tingenone (3), and iguesterin (4) were isolated from Triterygium regelii and dihydrocelastrol (5) was synthesized by hydrogenation under palladium catalyst. Isolated quinone-methide triterpenes (1-4) and 5 were evaluated for SARS-CoV 3CL pro inhibitory activities and showed potent inhibitory activities with IC 50 values of 10.3, 5.5, 9.9, and 2.6 lM, respectively, whereas the corresponding 5 having phenol moiety was observed in low activity (IC 50 = 21.7 lM). As a result, quinone-methide moiety in A-ring and more hydrophobic E-ring assist to exhibit potent activity. Also, all quinone-methide triterpenes 1-4 have proven to be competitive by the kinetic analysis.

SARS-CoV 3CL pro inhibitory effects of quinone-methide triterpenes from Tripterygium regelii