8beta hydroxy 3 o beta dextro glucopyranosyl ent labda 13 en 15,16 diol Antiherpes Diterpenes Dodonaea viscosa HSV-1 Herpes simplex virus 1 Human herpesvirus 1 IC 50 Sapindaceae antiviral activity antivirus agent article carbon nuclear magnetic resonance diterpene drug mechanism drug structure electrospray mass spectrometry ent 15epsilon ethoxylabdan 3alpha,8beta dihydroxy 13(14) en 15,16 olide ent 16epsilon hydroxylabdan 3alpha,8beta dihydroxy 13(14) en 15,16 olide ent-Labdanes heteronuclear multiple bond correlation heteronuclear single quantum coherence infrared spectroscopy nonhuman nuclear Overhauser effect plant extract priority journal proton nuclear magnetic resonance ultraviolet spectroscopy unclassified drug