Phosphodiesterase 5 inhibitors from Derris scandens - Chaichamnong, N; Temkitthawon, P; Khorana, N; Pitpakdeeanan, P; Taepavarapruk, P; Nuengchamnong, N; Siriwattanasathien, Y; Suksamrarn, A; Ingkaninan, K (Planta Med, 2018)