In contrast to previous findings (2) that did not confirm Marker's hypothesis (1) and native saponins showed spiroketal side chain characteristics, and in accord with Marker's suggestions, we isolated a nitrogenous steroidal saponin lacking a spiroketal moiety from the roots of Solanum paniculatum L. The structure of this new saponin, named jurubine (corresponding to the plant's vernacular designation "Jurubeba" indigenous to tropical Brazil), was established as (25S)-3β-amino-5α-furostane-22α,26-diol O(26)-β-D-glucopyranoside (I). Acid hydrolysis of jurubine afforded the sugar-free steroid jurubidine (C27H45NO2, (25S)-3β-amino-5α,22α-spirostane, VII), and enzymic cleavage using emulsin yielded the same VII, demonstrating spontaneous and stereospecific cyclization of the primary aglycone 3β-amino-5α-furostane-22α,26-diol (V) or its Δ22-unsaturated dehydration product VI under mild conditions. Jurubine (C33H57NO8, amorphous, [α]D -27.8° in pyridine) was characterized by its N-salicylidene derivative II (C40H61NO9, m.p. 176-177°, [α]D -34.9° in pyridine, -46.2° in CHCl3), N-4-bromobenzylidene derivative III (C40H60BrNO8, m.p. 195-200°, [α]D -34.5° in pyridine), and pentaacetyl derivative IV (C43H67NO13, m.p. 155-168°, [α]D -41.1° in pyridine). The structure I was proven via: acid/enzymic hydrolysis yielding D-glucose (identified by paper and thin-layer chromatography) and VII; dehydration of IV to furost-20(22)-ene derivative IX, hydrogenation to X, hydrolysis to XI (identical with XI from N-acetyljurubidine isomerization/hydrogenation/hydrolysis); oxidation of XI with Kiliani reagent to XII confirming glucose attachment at C-26 primary hydroxyl; β-glucosidase cleavage indicating β-D-pyranoside structure; and C-22 α configuration deduction from Hirschmann and Hirschmann's considerations (6).