Structurally diverse cucurbitane-type triterpenoids from the tubers of Hemsleya chinensis with cytotoxic activity.

Ten previously undescribed cucurbitane-type triterpenoids, namely hemslyencins A-F (1-6) and hemslyencosides A-D (7-10), together with twenty previously reported compounds (11-30), were isolated from the tubers of Hemsleya chinensis. Their structures were elucidated by unambiguous spectroscopic data (UV, IR, HR-ESI-MS, 1D and 2D NMR data). Hemslyencins A and B (1 and 2) possessing unique 9, 11-seco-ring system with a six-membered lactone moiety, were the first examples among of the cucurbitane-type triterpenoids, and hemslyencins C and D (3 and 4) and hemslyencoside D (10) are the infrequent pentacyclic cucurbitane triterpenes featuring a 6/6/6/5/6 fused system. The cytotoxic activities of all isolated compounds were evaluated against MCF-7, HCT-116, HeLa, and HepG2 cancer cells, and their structure-activity relationships (SARs) was discussed as well. Compounds 17, 25, and 26 showed significant cytotoxic effects with IC50 values ranging from 1.31 to 9.89 µM, among which compound 25 induced both apoptosis and cell cycle arrest at G2/M phase in a dose dependent manner against MCF-7 cells.

Five New C21 -Steroidal Sapogenins from the Acid Hydrolysate of Cynanchum otophyllum Roots.

Five new C21 -steroidal sapogenins (1-5) named cynotogenins J-N, were isolated from the acid hydrolysate of Cynanchum otophyllum roots. Their structures were established by extensive spectroscopic analysis (UV, IR, HR-ESI-MS, and NMR). Most notably, compounds 1-3 harboring a rare 5ß,6ß-epoxy group in the C21 -steroidal skeleton of Cynanchum plants. All compounds were evaluated for their cytotoxicities against multiple cancer cell lines, in which compounds 5 showed weak cytotoxicity against HepG2 cancer cells with IC50 values of 44.90 µM.

Three new cardenolides from the fruits of Cascabela thevetia (L.) Lippold and their cytotoxic activities.

Phytochemical investigations on the fruits of Cascabela thevetia (L.) Lippold led to obtain three new cardenolides (1-3) and five known analogues (4-7). Their structures were elucidated by means of UV, IR, HR-ESI-MS, 1D and 2D NMR spectroscopic data analysis. Compounds 1 and 2 represent the first examples of naturally occurring cardenolides with 19-nor-5(10)-ene group and α-l-3-demethyl-thevetose, respectively. Compound 3 is a rare C-nor-D-homocardenolide in nature. All isolated cardenolides (1-7) were evaluated for their cytotoxic activities against four human cancer cell lines (MCF-7, HCT-116, HeLa and HepG2), and the results indicated the compounds with sugar units (1, 2, 4, and 5) exhibited stronger cytotoxic activities with IC50 values ranging between 0.022 and 0.308 µM.

Design, Synthesis and Anticancer Activity of Novel Steroidal Derivatives with D-Ring Fused or Substituted N-Heterocyclic Systems.

A series of novel D-ring fused or substituted steroidal N-heterocycles were synthesized, and their chemical structures were characterized by spectroscopic analysis. The anticancer activity of these compounds against four human cancer cell lines (MCF-7, H1299, HeLa and HepG2) were evaluated and the structure-activity relationship (SAR) was also investigated. Compound 3c displayed significant inhibitory activity on the four cancer cells with IC50 values ranging from 3.88 to 10.05 µM. Overall, these studies indicated that construction of N-heterocyclic system with D-ring substituted containing a double bond at C-16 and C-17 or D-ring fused with [17,16-d]azolo[1,5-a]pyrimidine could be a promising strategy to improve antitumor activity for steroids deserved further investigation.

Synthesis and biological evaluation of 3ß-O-neoglycosides of caudatin and its analogues as potential anticancer agents.

In order to study the structure-activity relationship (SAR) of C21-steroidal glycosides toward human cancer cell lines and explore more potential anticancer agents, a series of 3ß-O-neoglycosides of caudatin and its analogues were synthesized. The results revealed that most of peracetylated 3ß-O-monoglycosides demonstrated moderate to significant antiproliferative activities against four human cancer cell lines (MCF-7, HCT-116, HeLa, and HepG2). Among them, 3ß-O-(2,3,4-tri-O-acetyl-ß-L-glucopyranosyl)-caudatin (2k) exhibited the highest antiproliferative activity aganist HepG2 cells with an IC50 value of 3.11 µM. Mechanical studies showed that compound 2k induced both apoptosis and cell cycle arrest at S phase in a dose dependent manner. Overall, these present findings suggested that glycosylation is a promising scaffold to improve anticancer activity for naturally occurring C21-steroidal aglycones, and compound 2k represents a potential anticancer agent deserved further investigation.

New C21-steroidal aglycones from the roots of Cynanchum otophyllum and their anticancer activity.

Naturally occurring C21-steroidal aglycones from Cynanchum exhibit significant antitumor effects. To expand the chemical diversity and get large scale C21-steroidal aglycones, the extracts of the roots of Cynanchum otophyllum were treated with 5% HCl in aqueous and the resulting hydrolysate was investigated. Nine new C21-steroidal aglycones (1-9) namely cynotogenins A-I, along with seventeen known analogous (10-26), were isolated from the hydrolysate. The structures of compounds 1-9 were elucidated by spectroscopic analysis (IR, HR-ESI-MS, 1D and 2D NMR) and comparison of observed spectroscopic data with those of reported in the literature. Aglycones 2-5 with rare cis-cinnamoyl group as well as 8 and 9 with 5ß,6ß-epoxy group were found from the genus of Cynanchum for the first time. The cytotoxicities of compounds 1-26 toward human cancer HeLa, H1299, HepG2, and MCF-7 cells were evaluated and preliminary structure-activity relationship (SAR) was discussed. Moreover, compound 20 inhibits HepG2 cell apoptosis and induces of G0/G1 phase arrest in a dose dependent manner.

Synthesis of C3-Neoglycosides of digoxigenin and their anticancer activities.

Cardiac glycosides exhibit significant anticancer effects and the glycosyl substitution at C3 position of digoxigenin is pivotal for their biological activity. In order to study the structure-activity relationship (SAR) of cardiac glycosides toward cancers and explore more potent anticancer agents, a series of C3-O-neoglycosides and C3-MeON-neoglycosides of digoxigenin were synthesized by the Koenigs-Knorr and neoglycosylation method, respectively. In addition, digoxigenin bisdigitoxoside and monodigitoxoside were prepared from digoxin by sodium periodate (NaIO4) oxidation and 6-aminocaproic acid hydrolysis. The SAR analysis revealed that C3-O-neoglycosides of digoxigenin exhibited stronger cytotoxicity and induction of Nur77 expression of tumor cells than C3-MeON-neoglycosides. Also, 3ß-O-glycosides exhibited stronger anticancer effects than 3α-O-glycosides. Among them, 3ß-O-(ß-l-fucopyranosyl)-digoxigenin (3i) showed the highest activity on induction of Nur77 expression and translocation from the nucleus to cytoplasm, leading to cancer cell apoptosis.

UGT74AN1, a Permissive Glycosyltransferase from Asclepias curassavica for the Regiospecific Steroid 3-O-Glycosylation.

A permissive steroid glycosyltransferase (UGT74AN1) from Asclepias curassavica exhibited robust capabilities for the regiospecific C3 glycosylation of cardiotonic steroids and C21 steroid precursors, and unprecedented promiscuity toward 53 structurally diverse natural and unnatural compounds to form O-, N-, and S-glycosides, along with the catalytic reversibility for a one-pot transglycosylation reaction. These findings highlight UGT74AN1 as the first regiospecific catalyst for cardiotonic steroid C3 glycosylation and exhibit significant potential for glycosylation of diverse bioactive molecules in drug discovery.

Synthesis of MeON-neoglycosides of digoxigenin with 6-deoxy- and 2,6-dideoxy-d-glucose derivatives and their anticancer activity.

Cardiac glycosides show anticancer activities and their deoxy-sugar chains are vital for their anticancer effects. In order to study the structure-activity relationship (SAR) of cardiac glycosides toward cancers and get more potent anticancer agents, a series of MeON-neoglycosides of digoxigenin was synthesized and evaluated. First, ten 6-deoxy- and 2,6-dideoxy-d-glucopyranosyl donors were synthesized starting from methyl α-d-glucopyranoside and 2-deoxy-d-glucose. Meanwhile, the digoxigenin was obtained by acidic hydrolysis of commercially available digoxin as glycosyl acceptor. Then, a 22-member MeON-neoglycoside library of digoxigenin was successfully synthesized by neoglycosylation method. Finally, the induction of Nur77 expression and its translocation from the nucleus to cytoplasm together with cytotoxicity of these MeON-neoglycosides were evaluated. The SAR analysis revealed that C3 glycosylation is required for their induction of Nur77 expression. Moreover, some MeON-neoglycosides (2b and 8b) could significant induce the expression of Nur77 and its translocation from the nucleus to cytoplasm. However, these compounds showed no inhibitory effects on the proliferation of cancer cells, suggesting that they may not induce apoptosis of NIH-H460 cancer cells and their underlying potential and application toward cancer cells deserves future study.

Cardiac glycosides from the bark of Antiaris toxicaria.

Five new cardiac glycosides (1-5, namely antiaroside Y-ZC) together with 19 known compounds were obtained from the bark of Antiaris toxicaria. Their chemical structures were determined by IR, HR-ESI-MS, 1D and 2D NMR (HSQC, (1)H-(1)H COSY, HMBC, ROESY). The absolute configuration of sugar unit was defined by acid hydrolysis and appropriate derivatization. Compound 1 was rare 5ß-H-10ß-H-19-nor-cardenolide, which might derive from decarboxylative derivative of 19-COOH cardenolide. The inhibitory effects of cardiac glycosides 1-11 on the viability of NIH-H460 lung cancer cells and their induction of Nur77 expression were evaluated and preliminary structure-activity relationship (SAR) was also discussed.