Selective inhibition of the cellular sodium pump by emicymarin and 14ß anhydroxy bufadienolides

Unified Total Synthesis of Five Bufadienolides

We report a unified total synthesis of five bufadienolides: bufalin (1), bufogenin B (2), bufotalin (3), vulgarobufotoxin (4), and 3-(N-succinyl argininyl) bufotalin (5). After the steroidal ABCD ring 8 was produced, the D ring was cross-coupled with a 2-pyrone moiety and stereoselectively epoxidized to generate 6. TMSOTf promoted a stereospecific 1,2-hydride shift from 6 to establish the β-oriented 2-pyrone of 19. Functional group manipulations from 19 furnished 1-5, which potently inhibited cancer cell growth.

Biotransformation of bufadienolides by cell suspension cultures of Saussurea involucrata

The biotransformation of three bioactive bufadienolides, namely, bufotalin (1), telocinobufagin (2), and gamabufotalin (3) by cell suspension cultures of Saussurea involucrata yielded 11 products. Bufotalin yielded 3-epi-bufotalin (1a), 3-epi-desacetylbufotalin (1b), 3-epi-bufotalin 3-O-β-D-glucoside (1c), 1β-hydroxybufotalin (1d), and 5β-hydroxybufotalin (1e); telocinobufagin yielded 3-dehydroscillarenin (2a), 3-dehydrobufalin (2b), and 3-epi-telocinobufagin (2c); and gamabufotalin yielded 3-epi-gamabufotalin (3a), 3-dehydrogamabufotalin (3b), and 3-dehydro-Δ¹-gamabufotalin (3c), respectively. Among these 11 products, 1a, 1b, 1c, 1d, 3a and 3c are previously unreported. The structures of these metabolites were elucidated based on NMR spectroscopic analyses and mass spectrometry. Most metabolites showed significant cytotoxic activities against human hepatoma (HepG2) and breast cancer (MCF-7) cell lines. In addition, the time course for the biotransformation of 3 was investigated.