The pentacyclic steroidal constituents of Tacca plantaginea: taccalonolide E and F

Abstract

Two pentacyclic steroidal bitter principles, taccalonolide E and F, have been isolated from Tacca Plantaginea. Their structures were elucidated by spectroscopic methods.The plant Tucca plantaginea (Hance) Drenth, which grows in tropical regions of China,' has been used as folk medicine for treatment of gastric ulcer, teeth and stomach ache, incised wounds as anti-inflammatory, antipyretic agent.4 The :investigation of this plant afforded several steroidal bitter principles, four of them, taccalonolide A, B,, C, D,* have been reported previously. Now we report the isolation and structure determination of two related compounds, taccalonolide E(l) and F(2), which were also isolated from the rhizome of T. plan taginea .Taccalonolide E(1), C,4H4,0,,. The IR spectrum of 1 showed the characteristic absorptions at 1810, 1730,1690 cm-1 which indicated the existence of en01 y-lactone and ketone functions. The lH NMR spectrum of 1 showed 8 methyl signals, 5 downfield protons and 2 epoxy protons. In comparison of the N M R spectrum of 1 with that of taccalonolide A (3), we found they were rather similar, the only difference between two compounds was that the signal of 11-H at 65.25 (dd) and one acetyl-CH, at 6 1 .92 in the NMR of 3 were absent in that of 1, and the signal at 65.20 (d, 12-H) of 3 shifted to 64.98 (dd) in 1, and in 'H NMR of 1 an extra signal appeared at 61.70 (m, 2H). By decoupling experiments, the signal at 61.70 (m) was shown to couple both with 12-H signal (64.98, dd) and 9-H signal (62.13, m), which suggested that it was the signal of two ll-H protons. It indicates that taccalonolide E is des-llacetoxy taccalonolide A, in agreement with the molecular formula of 1. Therefore, the structure of taccalonolide E (1) was elucidated as 1-a, 12-01, 15-u-triacetoxy-2-a, 3-u-epoxy-24-D-25-u-dimethyl and 7+, 25-p-dihydroxy substituted.Taccalonolide F (2), derivate of the parent hydrocarbon. C,,H,,O,,, just one oxygen atom more than 1. 2 had a similar IR spectrum to that of 1, it showed that 2 and 1 has the same pentacyclic steroidal skeleton. In IH NMR spectrum, there were signals at downfield 64.77 (d) and 64.03 (dd) coupled with each other, we assigned that to be signals of 12-H and ll-H respectively. The signal of ll-H (64.03, dd) appeared at upper field suggesting the existence of a Il-hydroxy group, which would cause the signal of 12-H to shift upperfield too. Furthermore, we found that the coupling constant between the signal of ll-H

Syntheses, Crystal Structures, and Spectral Characterization of Six Novel Benzimidazolyl Substituted Triaryltriazoles

“…Recently, a series of asymmetrically 3,4,5triarylsubstituted 1,2,4-triazoles and their metal complexes have been synthesized by our group [7][8][9][10][11][12][13][14][15][16][17]. However, most of the substituted groups on the 1,2,4-triazoles are pyridyl, phenyl, quinolyl, and five-membered aromatic rings such as pyrrolyl and imidazolyl.…”

Cytotoxic Taccalonolides and Withanolides from Tacca chantrieri

“…5). Ten known compounds were identified as taccalonolide A (9) [11], taccalonolide B (10) [11], taccalonolide C (11) [30], taccalonolide E (12) [31], taccalonolide L (13) [32], taccalonolide K (14) [33], taccalonolide N (15) [34], taccalonolide P (16) [28], taccalonolide R (17) [34], and taccalonolide Y (18) [23] by comparison of their spectroscopic data with those reported. Among them, compounds 11, 13, 14, 16, and 18 were not previously reported from T. chantrieri.…”

Plantagiolide F, a minor withanolide fromTacca plantaginea

“…Recent chemical and pharmaceutical investigations on this species have demonstrated that taccalonolides A and E were the first natural steroids to show microtubule-stabilising activity (Tinley et al, 2003). Besides taccalonolides A and E, 11 other highly oxygenated taccalonolides have been isolated from this species (Z. Chen, Wang, & M. Chen, 1987;Chen, Wang, & Shen, 1988;Shen, Chen, & Gao, 1991, 1996Shen, Chen, Gao, & Wichtl, 1997). Our previous chemical investigation of this plant led to the isolation of four new steroidal saponins; five new withanolides, plantagiolides A-E and three new taccalonolides (Liu & Chen, 2002;Liu, Ni, Hao, & Chen, 2006;Yang et al, 2008).…”