Diphenethylpiperidine alkaloids with tracheal smooth muscle relaxation activity from Hippobroma longiflora (L.) G. Don - Chan, Z Y; Govindaraju, K; Krishnan, P; Low, Y Y; Chong, K W; Yong, K T; Ting, K N; Lim, K H (Phytochem Lett, 2019)