Spirostanol Saponins from Flowers of Allium Porrum and Related Compounds Indicating Cytotoxic Activity and Affecting Nitric Oxide Production Inhibitory Effect in Peritoneal Macrophages

Saponins, a diverse group of natural compounds, offer an interesting pool of derivatives with biomedical application. In this study, three structurally related spirostanol saponins were isolated and identified from the leek flowers of Allium porrum L. (garden leek). Two of them were identical with the already known leek plant constituents: aginoside (1) and 6-deoxyaginoside (2). The third one was identified as new component of A. porrum; however, it was found identical with yayoisaponin A (3) obtained earlier from a mutant of elephant garlic Allium ampeloprasun L. It is a derivative of the aginoside (1) with additional glucose in its glycosidic chain, identified by MS and NMR analysis as (2 ff, 3 fi, 6 fi, 25R)-2,6-dihydroxyspirostan-3-yl fi-D-glucopyranosyl-(1 ! 3)- fi-D-glucopranosyl-(1 ! 2)-[ fi-D-xylopyranosyl-(1 ! 3)]- fi-D-glucopyranosyl]-(1 ! 4)- fi-Dgalactopyranoside, previously reported also under the name alliporin. The leek native saponins were tested together with other known and structurally related saponins (tomatonin and digitonin) and with their related aglycones (agigenin and diosgenin) for in vitro cytotoxicity and for effects on NO production in mouse peritoneal cells. The highest inhibitory effects were exhibited by 6deoxyaginoside. The obtained toxicity data, however, closely correlated with the suppression of NO production. Therefore, an unambiguous linking of obtained bioactivities of saponins with their expected immunobiological properties remained uncertain.

Automated summary

In this study, three structurally related spirostanol saponins were isolated and identified from leek flowers. One of them is a new component, while the other two are identical to known constituents of leek plants. The cytotoxicity and effects on NO production in mouse peritoneal cells of these saponins were tested, with 6-deoxyaginoside showing the highest inhibitory effects and a close correlation between toxicity and NO production inhibition observed.