Table 1: The IC50 and K i ( M) values of S-petasin and reference drugs on PDE isozymes 1–5.

Test compoundPDE isozyme
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S-Petasin
 IC50>100 (n = 3)>100 (n = 3)25.5 ± 1.5 (n = 4)17.5 ± 2.4 (n = 6)*>100 (n = 3)
K iNDND25.3 ± 2.0 (n = 4)18.1 ± 1.7 (n = 4)*ND
Reference drugsa
 IC5036.5 ± 8.8 (n = 4)6.5 ± 1.0 (n = 4)1.5 ± 0.2 (n = 8)6.9 ± 0.6 (n = 4)4.1 ± 1.1 (n = 4)
K iNDND1.6 ± 0.2 (n = 4)4.2 ± 0.7 (n = 4)ND

All values are expressed as the mean ± SEM (n), and n is the number of experiments. ND, not determined.
aReference drugs for PDE isozymes 1, 2, 3, 4 and 5 were vinpocetin, EHNA, milrinone, Ro 20-1724 and zaprinast, respectively.
, compared to the corresponding value of PDE3.