New Acetylcholinesterase‐Inhibitory Pregnane Glycosides of Cynanchum atratum Roots

Abstract Three new pregnane glycosides, cynatroside A ( 1 ), cynatroside B ( 2 ), and cynatroside C ( 3 ), isolated from the roots of Cynanchum atratum (Asclepiadaceae), were characterized as 7 β ‐{[ O ‐ α ‐ L ‐cymaropyranosyl‐(1→4)‐ O ‐ β ‐ D ‐digitoxopyranosyl‐(1→4)‐ β ‐ D ‐oleandropyranosyl]oxy}‐3,4,4a,4b,5,6,7,8,10,10a‐decahydro‐6 α ‐hydroxy‐4b‐ methyl‐2‐(2‐methyl‐3‐furyl)phenanthren‐1(2 H )‐one ( 1 ), 7 β ‐{[ O ‐ β ‐ D ‐cymaropyranosyl‐(1→4)‐ O ‐ α ‐ L ‐diginopyranosyl‐(1→4)‐ β ‐ D ‐cymaropyranosyl]oxy}‐3,4,4a,4b,5,6,7,8,10,10a‐decahydro‐2,6 α ‐dihydroxy‐4b‐methyl‐2‐(2‐methyl‐3‐furyl)phenanthren‐1(2 H )‐one ( 2 ), and 7 β ‐{[ O ‐ α ‐ L ‐cymaropyranosyl‐(1→4)‐ O ‐ β ‐ D ‐digitoxopyranosyl‐(1→4)‐ β ‐ L ‐cymaropyranosyl]oxy}‐3,4,4a,4b,5,6,7,8,10,10a‐decahydro‐2,6 α ‐dihydroxy‐4b‐methyl‐2‐(2‐methyl‐3‐furyl)phenanthren‐1(2 H )‐one ( 3 ), respectively. In addition, ten known constituents were identified, i.e. , cynascyroside D ( 4 ), glaucoside C ( 5 ), glaucoside D ( 6 ), atratoside A ( 7 ), 2,4‐dihydroxyacetophenone ( 8 ), 4‐hydroxyacetophenone ( 9 ), syringic acid ( 10 ), azelaic acid ( 11 ), suberic acid ( 12 ), and succinic acid ( 13 ). Among these compounds, 1 – 4 significantly inhibit acetylcholinesterase activity.