Quillajasides A and B: New Phenylpropanoid Sucrose Esters from the Inner Bark of Quillaja saponaria Molina

摘要

The phenolic composition of freshly prepared aqueous extracts of the inner bark of Quillaja saponaria Molina was compared to that of commercially available Quillaja extracts, which are currently used as emulsifiers in foods and cosmetics. Major phenolics in both extracts were (+)-piscidic acid and several p-coumaroyl sucrose esters. Among the latter, two new compounds were isolated and characterized: alpha-L-rhap-(1 -> 4)-alpha-L-rhap-(1 -> 3)-(4-O-(E)-p-coumaroyl)-alpha-D-glup-(1 -> 2)-(3-O-(E)-p-coumaroyl)-beta-D-fruf (quillajaside A) and beta-D-apif-(1 -> 4)-alpha-L-rhap-(1 -> 4)-alpha-L-rhap-(1 -> 3)-(4-O-(E)-p-cournaroyl)-alpha-D-glup-(1 -> 2)-(3-O-(E)-p-coumaroyl)-beta-D-fruf (quillajaside B). In addition, a putative biosynthetic pathway of at least 20 structurally related p-coumaroyl sucrose esters was tentatively identified. Besides their antioxidant activity and their potential function as substrate for enzymatic browning reactions, the new compounds are highly characteristic for both the inner bark of Q. saponaria and commercial extracts derived therefrom. Consequently, they might serve as authenticity markers for the detection of Quillaja extracts in food and cosmetic formulations.