“…The substrate Z-Phe-Arg-7-amino-4-methylcoumarin hydrochloride was acquired from Bachem (Bubendorf, Switzerland).The fluorescence proteinase activity assay was performed using an Infinite F200PRO fluorescent plate reader spectrophotometer (TECAN, Männedorf, Switzerland). The natural compounds agathisflavone (1) (Alves et al, 2012;Correia et al, 2006;Mbing et al, 2006), tetrahydrorobustaflavone (2) (Correia et al, 2006;Kassem et al, 2004) and 3-oxo-urs-12-en-28-oic acid (3) (de Sousa et al, 2014a) were isolated in our laboratory and characterized by NMR ( 1 H and 13 C, DEPT-135, HSQC, and HMBC) and mass spectroscopy comparing to literature data. Quercetin hydrate (4) ≥97% was purchased from Sigma Aldrich (337951).…”