The flavonoids and phenolic acids of the genus Silphium and their chemosystematic and medicinal value
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My chemistry studies of the genus Silphium involved the flavonoids and phenolic acids among eleven species. In the course of these investigations, five new flavonol triglycosides were isolated and characterized: isorhamnetin 3-O-α-L-rhamnosyl (1'''→6'')- O-β-D-galactopyranoside 7-O-β-L-apiofuranoside (1A), quercetin 3-O-α-L-rhamnosyl (1'''→6'')-O-β-D-galactopyranoside 7-O-β-L-apiofuranoside (2A), quercetin 3-O-β-Lgalactosyl (1'''→6'')-O-β-D-rhamnopyranoside 7-O-α-L-apiofuranoside (3A), kaempferol 3-O-β-D-apiofuranoside 7-O-α-L-rhamnosyl (1''''→6''')-O-β-D-galactopyranoside (4A) and kaempferol 3-O-β-D-apiofuranoside 7-O-α-L-rhamnosyl (1''''→6''')-O-β-D (2'''-O-E- caffeoylgalactopyranoside) (5A). Many other known mono and diglycosidic flavonoids were also isolated and identified. The structures of all these compounds were established by chemical methods and spectral analyses using 1 H NMR, 13C NMR, HMQC, HMBC, ROESY, TOCSY and LC/MS techniques. The distribution of the flavonoids and phenolic acids in all eleven members were compared with Dr. Jennifer Clevinger’s DNA-based revision of the genus. In addition to the detailed chemical investigations, I present my evaluations of the chemosystematic and medicinal value of the compounds I characterized; moreover, the new flavonoids are now being made available for medicinal and pharmaceutical studies.