S-Petasin, the Main Sesquiterpene of Petasites formosanus, Inhibits Phosphodiesterase Activity and Suppresses Ovalbumin-Induced Airway Hyperresponsiveness

Table 1

The IC₅₀ and K _i (𝜇M) values of S-petasin and reference drugs on PDE isozymes 1–5.

Test compound	PDE isozyme
	1	2	3	4	5
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 i	ND	ND	25.3 ± 2.0 (n = 4)	18.1 ± 1.7 (n = 4)*	ND
Reference drugs^a
IC50	36.5 ± 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 i	ND	ND	1.6 ± 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.
^∗𝑃<.05, compared to the corresponding value of PDE3.