Phenylpropanoids from Rhodiola fastigiata (Hook.f. & Thomson) Fu (Crassulaceae) and their antiplasmodial activities

(7R,8S,7'R,8'R)-4'-hydroxy-4-methoxy-7,7'-epoxylignan (1), a tetrahydrofuran lignan, was isolated from Rhodiola fastigiata, together with two known tetrahydrofuran lignans (2 and 3), one known biphenyl neolignan (4), four known simple phenylpropanoids (5-8), and one known isocoumarin (9). Compound 1 was previously mentioned in our patent CN118955435A. However, its complete spectroscopic characterisation (1D and 2D NMR, HR-ESI-MS) as well as its antiplasmodial activity with IC₅₀ values were reported here for the first time. The absolute configuration of compound 1 was determined by electronic circular dichroism (ECD) spectroscopy, while that of compound 2 was established by specific rotation and ECD. Compounds 2-6 were isolated from the genus Rhodiola for the first time; Notably, compound 2 was previously isolated as a racemate enriched in the (-)-enantiomer. In contrast, the (+)-enantiomer was obtained as the sole isolable form from R. fastigiata in the present study, representing the first isolation of this enantiomer in pure form. In vitro antiplasmodial activity of compounds 1-4, 6-9 against Plasmodium falciparum strain 3D7 was evaluated by the SYBR Green I method. Compounds 1-4 exhibited potent activity with IC₅₀ values of 4.88, 9.01, 12.01, and 8.91 µM, respectively.