Minor saponins from the sea cucumber Cucumaria frondosa

The structures of three saponins from Cucumaria frondosa have been determined principally by high field ID and 2D NMR data. Frondoside F 5 is shown to possess the structure 3B-O-(3-O-methyl-6-sulfonato-beta -D-glucopyranosyl-(1 -->3)-O-beta -D-6-sulfonato-glucopyranosyl-(1 -->4)-O-[beta -D-xylopyranosyl-(1 -->2)]-O-beta -D-quinovopyranosyl-(1 -->2)-O-beta -D-w4-sulfonato-xylopyranosyly) -17 alpha -hydroxy-20R-acetoxy-22R-hydroxy-5 alpha -lanost-24-ene-18-carboxylic acid (18-22) lactone, trisodium salt and represents a new class of holothurin distinguished by its C-18-22 lactone. Frondoside E-2 7 is 3 beta -O-(3-O-methyl-beta -D-glucopyranosyl(1 -->3)-O-beta -D-glucopyranosyl-(1 -->4)-O-[beta -D-xylopyranosyl(1 -->2)]-O-beta -D- quinovopyranosyl-(1 -->2)-O-beta -D-4-sulfonatopyranosyl)-holosta-9(11),24-dien-16-one, sodium (or potassium) salt, while frondoside E-1 6 is found to be identical with previously reported cucumarioside A(2)-2 from C. japonica.