Absolute Configuration of Periplosides C and F and Isolation of Minor Spiro-orthoester Group-Containing Pregnane-type Steroidal Glycosides from Periploca sepium and Their T-Lymphocyte Proliferation Inhibitory Activities

Further phytochemical investigation of the root bark of Periploca sepium afforded nine new spiro-orthoester group-containing pregnane-type glycosides termed periplosides O-V and 3-O-formyl-periploside A. The structures of these glycosides along with the absolute configuration of the unique seven-membered formyl acetal-bridged spiro-orthoester function and the 4,6-dideoxy-3-O-methyl-Δ³-2-hexosulosyl moiety were elucidated on the basis of spectroscopic data interpretation and chemical transformation. The absolute configurations of the major compounds periplosides C and F were established by single-crystal X-ray diffraction analysis. The isolated compounds were evaluated for their inhibitory activities against the proliferation of T-lymphocytes. As a result, periploside C, the most abundant glycoside containing a spiro-orthoester moiety found in the plant, exhibited the most favorite selective index value (SI = 82.5). The length and constitution of the saccharide chain in the periplosides were found to influence the inhibitory activity and the SI value.

Metajapogenins A-C, Pregnane Steroids from Shells of Metaplexis japonica

Phytochemical investigation of the shells of Metaplexis japonica (Thunb.) Makino, belonging to the family of Apocynaceae, afforded three new pregnane steroids, metajapogenins A–C, along with three known compounds. The structures of the new compounds were elucidated as 12β,14β,17β-trihydroxypregna-3,5-dien-7,20-dione, 12β,14β,17β,20β-tetrahydroxypregna-3,5-dien-7-one; 3β,12β,14β,17β-tetrahydroxypregn-5-ene-7,20-dione on the basis of extensive spectroscopic evidence derived from 1D; 2D-NMR experiments and mass spectrometry. The known compounds included pergularin; 12-O-acetylpergularin; and pergularin-3-O-β-d-oleandropyranose; which were identified for the first time in the shells of M. japonica.

New Sweet-Tasting C21-Pregnane Glycosides from Pericarps of Myriopteron extensum

Ten novel C21 pregnane glycosides, extensumside C-L (1-10), were isolated as highly sweet-tasting substances from the edible pericarps of Myriopteron extensum (Wight) K. Schum by sensory-guided fractionation and purification. Their structures were determined through 1D and 2D NMR, such as HSQC, HMBC, ¹H-¹H COSY, HSQC-TOCSY, and ROESY, as well as other spectroscopic analysis combined with chemical evidence. These compounds shared the same aglycone, 3β,16α-dihydroxy-pregn-5-en-20-one, and contained the deoxysugar chain and the glucose chain which were linked to C-3 and C-16 of the aglycone, respectively. The sweetness potency was evaluated by a human sensory panel test and preliminary structure-taste relationship was discussed. The sweetness intensities of these compounds are between 50 and 400 times greater than that of sucrose. Furthermore, quantitation analyses of compounds 1, 3, 4, and 6 in different parts of M. extensum indicated that the concentrations of these sweet components in the pericarps are obviously higher than those in stems and roots.

Two New 8, 14-seco-pregnane Steroidal Aglycones froni Roots of Cynanchum bungei

Two new 8, 14-seco skeleton C(21) steroidal aglycones, cynanbungeigenin A (1) and cynanbungeigenin B (2), were isolated from the hydrolyzed extract of the EtOAc soluble extract of the roots of Cynanchum bungei. Their structures were determined on the basis of chemical evidence and extensive spectroscopic methods, including 1D and 2D NMR spectroscopy.

Insecticidal Pregnane Glycosides from the Root Barks of Periploca sepium

To explore novel lead compounds for botanical pesticides from natural sources, a new pregnane glycoside (periplocoside) P2 as well as its isomer, a known pregnane glycoside P1, were isolated from the root barks of Periploca sepium using a bioactivity-guided method, and their structures were confirmed by ID NMR, 2D NMR, IR, ESI-MSn and HRMS. Their insecticidal activities were evaluated against 3rd instar larvae of M separata, and the results indicated that P2 exhibited excellent insecticidal activity with LC₅₀ values of 2.9 and 2.2 mg/mL after 24 and 48 h, respectively, much lower than those of the positive control celangulin-V (24.7 and 21.0 mg/mL after 24 and 48 h, respectively). This work demonstrated that pregnane glycosides from Periploca sepium could be promising lead compounds for developing botanical pesticides urgently needed in agriculture.

Polyoxypregnane steroids with an open-chain sugar moiety from Marsdenia tenacissima and their chemoresistance reversal activity

A polyoxypregnane aglycone, 12β-O-acetyl-11α-O-isobutyryltenacigenin B, and four polyoxypregnane glycosides with a pachybionic acid ester moiety, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-oleandronyl)-11α-O-isobutyryltenacigenin B, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-oleandronyl)-11α-O-tigloyltenacigenin B, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-oleandronyl)-11α-O-2-methylbutyryltenacigenin B, and 12β-O-acetyl-3-O-(β-D-glucopyranosyl-(1→4)-6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-D-oleandronyl)-11α-O-tigloyltenacigenin B, were isolated from the canes of Marsdenia tenacissima, together with a disaccharide derivative. Their structures were elucidated by extensive spectroscopic analysis, and the absolute configurations were further determined by X-ray crystallographic analysis. With the exception of the disaccharide derivative, all five compounds are unusual naturally occurring polyoxypregnane glycosides bearing an open-chain sugar moiety. Two of these exhibit a wide spectrum of chemoresistance reversal activity, and potential mechanisms were studied accordingly.

Pregnane-10,2-carbolactones from a Hawaiian Marine Sponge in the Genus Myrmekioderma

Four new pregnanes, 3β,4β-dihydroxy-17-methyl-17α-pregna-5,13-diene-10,2-carbolactone (1), 6β-chloro-3β-hydroxy-17-methyl-17α-pregna-4,13-diene-10,2-carbolactone (2), 3β-hydroxy-6β-methoxy-17-methyl-17α-pregna-4,13-diene-10,2-carbolactone (3), and 3β,6β-dihydroxy-17-methyl-17α-pregna-4,13-diene-10,2-carbolactone (4), were isolated from an undescribed species of Myrmekioderma Ehlers along with the known pregnane carbolactone (5). The structures of the new compounds were determined by spectroscopic methods and comparison with previously described compounds. Compound 5 showed almost 4-fold activation of pregnane X receptor, while 2 inhibited BACE1 with an IC50 value of 82 μM.

Bioactive Octahydroxylated C21 Steroids from the Root Bark of Lycium chinense

Lyciumsterols A-K (1-11), 11 new octahydroxylated C21 steroids, were isolated from the root bark of Lycium chinense, along with 15 known compounds. Characterization of these C21 steroids showed the presence of eight hydroxy groups on the C21 steroid skeleton with a (2E,4E)-5-phenyl-2,4-pentadienoate group at C-12 or C-20 and various 2,6-deoxy sugar residues at C-3. The structures of these compounds were elucidated using spectroscopic data interpretation. Compounds 2, 3, and 7 exhibited dose-dependent protective effects on pancreatic islet cells and may help to improve cell viability. In addition, it was found that compounds 7, 8, 9, and 11 exhibited autophagy activation.

Pregnane steroids from a gorgonian coral Subergorgia suberosa with anti-flu virus effects

Five new pregnane-type steroids namely subergorgols T-X (1-5) and three known analogues (6-8) were isolated from a gorgonian coral Subergorgia suberosa. The structures of new compounds were determined on the basis of extensive spectroscopic (IR, MS, 1D and 2D NMR) data analyses, in association with photochemical transformation and ECD methods for the configurational assignment. Compounds 1-8 were evaluated for the inhibitory effects against H1N1 virus infected in MDCK cells, while subergorgols T-U and 1,2-dehydroprogesterone exerted potent inhibition against A/WSN/33 virus.

Identification and Evaluation of Antiepileptic Activity of C21 Steroidal Glycosides from the Roots of Cynanchum wilfordii

Nine new C21 steroidal glycosides, named cynawilfosides A-I (1-9), along with 12 known compounds were isolated from the roots of Cynanchum wilfordii. The structures of the new compounds were elucidated by spectroscopic analysis and chemical methods. The five major components, cynawilfoside A (1), cynauricoside A (11), wilfoside C1N (16), wilfoside K1N (17), and cyanoauriculoside G (18), exhibited significant protection activity in a maximal electroshock (MES)-induced mouse seizure model with ED50 values of 48.5, 95.3, 124.1, 72.3, and 88.1 mg/kg, respectively.

Cytotoxicity of pregnane glycosides of Cynanchum otophyllum

Fourteen new pregnane glycosides, including nine caudatin glycosides (1-9), three qinyangshengenin glycosides (10-12), one kidjoranin glycosides (13) and one gagaminin glycosides (14), along with twelve known analogs (15-26) were isolated from roots of Cynanchum otophyllum Schneid. Their structures were deduced by detailed analysis of 1D and 2D NMR spectra, as well as HRESIMS. In this study, all pregnane glycosides obtained (1-26) were evaluated for their cytotoxic activities using three cancer cell lines (HepG2, Hela, U251). As results, except 6 and 10, other twenty-four pregnane glycosides showed cytotoxicities at different degrees against three cell lines.

Sixteen novel C-21 steroidal glycosides from the roots of Cynanchum mooreanum

Fourteen novel 14,15-diseco-18-nor-pregnane-type steroidal glycosides, mooreanoside A-C (1-3) and mooreanoside F-P (6-16) and two new 14,15-diseco-pregnane-type steroidal glycosides, mooreanoside D-E (4-5) were isolated from the roots of Cynanchum mooreanum Hemsl. Their structures were determined on the basis of spectroscopic and chemical analysis. Compounds 1-6, 8-10, 12-14 and 16 were tested for their immunological activities in vitro against Con-A induced proliferation of mice splenocytes.

Scalable C-H Oxidation with Copper: Synthesis of Polyoxypregnanes

Steroids bearing C12 oxidations are widespread in nature, yet only one preparative chemical method addresses this challenge in a low-yielding and not fully understood fashion: Schönecker's Cu-mediated oxidation. This work shines new light onto this powerful C-H oxidation method through mechanistic investigation, optimization, and wider application. Culminating in a scalable, rapid, high-yielding, and operationally simple protocol, this procedure is applied to the first synthesis of several parent polyoxypregnane natural products, representing a gateway to over 100 family members.

Two new 13,14:14,15-disecopregnane-type compounds from the roots of Cynanchum paniculatum

Two new 13,14:14,15-disecopregnane-type compounds glaucogenin F (1), glaucogenin F 3-O-β-D-oleandropyranoside (2), together with three known compounds cynapanoside A (3), cynatratoside A (4), and neocynapanogenin F 3-O-β-D-oleandropyranoside (5) were isolated from the 95% ethanol extract of the roots of Cynanchum paniculatum. The structures of new compounds were elucidated on the basis of extensive spectroscopic analyses, including 1D and 2D NMR, HRESIMS and NOESY.

Calotroposides H-N, new cytotoxic oxypregnane oligoglycosides from the root bark of Calotropis procera

As a part of our continuing interest in identifying anticancer drug leads from natural sources, we have investigated the n-BuOH fraction of the root bark of Calotropis procera (Ait) R. Br. Seven new oxypregnane oligoglycosides: calotroposides H-N (1-7) were isolated and identified. Their structures were established on the basis of 1D and 2D NMR studies, HRMS, and GCMS spectral data. The in vitro growth inhibitory activity of the n-BuOH fraction and compounds 1-7 was evaluated against A549 non-small cell lung cancer (NSCLC), U373 glioblastoma (GBM), and PC-3 prostate cancer cell lines. Compounds 4 and 6 showed subnanomolar growth inhibition activity with IC50 ranging from 0.5 to 0.7μM against U373 glioblastoma (GBM) and PC-3 prostate cancer cell lines. These results provide further insight into the chemical diversity and biological activities of this class of compounds.

Total synthesis of periploside A, a unique pregnane hexasaccharide with potent immunosuppressive effects

Periploside A is a pregnane hexasaccharide identified from the Chinese medicinal plant Periploca sepium, which features a unique seven-membered formyl acetal bridged orthoester (FABO) motif and potent immunosuppressive activities. Here, we show the synthesis of this molecule in a total of 76 steps with the longest linear sequence of 29 steps and 9.2% overall yield. The FABO motif is constructed via a combination of Sinaÿ's and Crich's protocol for the formation of orthoester and acetal glycosides, respectively. The 2-deoxy-β-glycosidic linkages are assembled stereoselectively with judicious choice of the glycosylation methods. The epimer at the spiro-quaternary carbon in the FABO motif has also been elaborated in a stereo-controlled manner. This epimer, as well as the synthetic analogues bearing the FABO motif, retain largely the inhibitory activities of periploside A against the proliferation of T-lymphocyte, indicating the importance of the chemical connection of the FABO motif to their immunosuppressive activity.

New polyoxypregnane glycosides from the roots of Marsdenia tenacissima

For the first time, a systematic phytochemical study was performed on the roots of Marsdenia tenacissima. Finally, sixteen new polyoxypregnane glycosides, marstenacissides A1-A7 (1-7) and marstenacissides B1-B9 (8-16), were isolated from M. tenacissima roots. The structures of these new compounds were established by various spectroscopic techniques, including 1D and 2D NMR spectroscopy and mass spectrometry.

Identification of cortisol metabolites in the bile of Atlantic cod Gadus morhua L

Interpretation of plasma cortisol levels in wild-caught fish is confounded by the stress of capture. Measurement of cortisol metabolites in fish bile could provide a method for assessing the stress level of wild fish because the time-lag for metabolism, conjugation and excretion into bile avoids the effects of sampling stress. To determine which biliary metabolite(s) to target, four Atlantic cod, Gadus morhua L., were injected with radioactive cortisol. After 22 h, the bile was collected and found to contain 30% of the injected activity. Cortisol metabolites were extracted from diluted bile samples using solid phase extraction and the radioactive metabolites separated by several different chromatographic procedures. The metabolites were predominantly present as sulfates (95%) with the remainder being glucuronidated. Chromatography split the sulfates into at least seven peaks, and acid solvolysis (which removes sulfate groups from steroids) generated four major radioactive steroids. These were identified, using microchemical reactions and re-crystallization to constant specific activity, as: 11β,17,21-trihydroxypregn-4-ene-3,20-dione (cortisol), 3α,11β,17,21-tetrahydroxy-5β-pregnan-20-one (tetrahydrocortisol; THF), 3α,17,21-trihydroxy-5β-pregnane-11,20-dione (tetrahydrocortisone; THE) and 3α,17,20β,21-tetrahydroxy-5β-pregnan-11-one (β-cortolone). The last of these was the most abundant, and thus a likely target for a biliary stress assay. Studies were also carried out to determine the best method for extraction and solvolysis of sulfates. Solid phase extraction (i.e. using octadecylsilane) was found to be too unreliable for routine use. Even though the extraction efficiency could be improved by acidifying the bile, this caused premature solvolysis of sulfated steroids. Acid solvolysis of unextracted bile worked best (c. 90% converted to free steroids) on volumes that were 1 μL or lower. Aryl sulfatase digestion of unextracted bile did not work well (only 20% of radioactivity was converted to free steroids).

Pregnane-type steroidal glycosides from Gymnema griffithii Craib

Eight pregnane-type steroidal glycosides substituted with ortho-acetate groups were isolated from the methanolic extract of the pericarp of Gymnema griffithii fruits, and named gymnemogriffithosides A-H. Their structures were determined by spectroscopic analysis (one and two dimensional nuclear magnetic resonance, high resolution electrospray ionization mass spectrometry and attenuated total reflectance-Fourier transformed infrared spectroscopy), while the absolute structure of the steroidal skeleton of one of these was additionally determined using Mosher's method. All compounds were evaluated for their in vitro (i) cytotoxic effects against five human tumor cell lines (BT 474, Chago, Hep-G2, KATO-III and SW620) and (ii) α-glucosidase inhibitory activity.

Novel oxazolinyl derivatives of pregna-5,17(20)-diene as 17α-hydroxylase/17,20-lyase (CYP17A1) inhibitors

New oxazolinyl derivatives of [17(20)E]-pregna-5,17(20)-diene: 2'-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4',5'-dihydro-1',3'-oxazole 1 and 2'-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4',4'-dimethyl-4',5'-dihydro-1',3'-oxazole 2 were evaluated as potential CYP17A1 inhibitors in comparison with 17-(pyridin-3-yl)androsta-5,16-dien-3β-ol 3 (abiraterone). Differential absorption spectra of human recombinant CYP17A1 in the presence of compound 1 (λmax=422 nm, λmin=386 nm) and compound 2 (λmax=416 nm) indicated significant differences in enzyme/inhibitors complexes. CYP17A1 activity was measured using electrochemical methods. Inhibitory activity of compound 1 was comparable with abiraterone 3 (IC50=0.9±0.1 μM, and IC50=1.3±0.1 μM, for compounds 1 and 3, respectively), while compound 2 was found to be weaker inhibitor (IC50=13±1 μM). Docking of aforementioned compounds to CYP17A1 revealed that steroid fragments of compound 1 and abiraterone 3 occupied close positions; oxazoline cycle of compound 1 was coordinated with heme iron similarly to pyridine cycle of abiraterone 3. Configuration of substituents at 17(20) double bond in preferred docked position corresponded to Z-isomers of compounds 1 and 2. Presence of 4'-substituents in oxazoline ring of compound 2 prevents coordination of oxazoline nitrogen with heme iron and worsens its docking score in comparison with compound 1. These data indicate that oxazolinyl derivative of [17(20)E]-pregna-5,17(20)-diene 1 (rather than 4',4'-dimethyl derivative 2) may be considered as potential CYP17A1 inhibitor and template for development of new compounds affecting growth and proliferation of prostate cancer cells.

Polyoxypregnane steroids from the stems of Marsdenia tenacissima

A new polyoxypregnane aglycone, tenacigenin D (1), and seven new C21 steroid glycosides, tenacissimosides D-J (2-8), were isolated from the stems of Marsdenia tenacissima. Their structures were determined by interpretation of their 1D and 2D NMR and other spectroscopic data, as well as by comparison with published values for related known compounds. Compound 1 was found to circumvent P-glycoprotein (P-gp)-mediated multidrug resistance through an inhibitory effect on P-gp with a similar potency to verapamil. In addition, compound 1 potentiated the activity of erlotinib and gefitinib in epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI)-resistant non-small-cell lung cancer cells.

New steroidal glycosides from the rhizome of Anemarrhena asphodeloides

Two new steroidal saponins, timosaponin X (1) and timosaponin Y (2), and one new pregnane glycoside, timopregnane B (3), were isolated from the rhizomes of Anemarrhena asphodeloides, as well as three known compounds 25S-timosaponin BII (4), protodesgalactotigonin (5), and timosaponin BII-a (6) isolated from this plant for the first time. By the detailed analysis of 1D, 2D NMR, MS spectra, and chemical evidences, the structures of new compounds were elucidated as 26-O-β-d-glucopyranosyl-(25S)-5β-22-methoxy-furost-3β,26-diol 3-O-β-d-glucopyranosyl-(1 → 2)-α-l-arabinopyranoside (1), 5β-pseudo-spirost-3β,15α,23α-triol 3-O-β-d-glucopyranosyl-(1 → 2)-β-d-galactopyranoside (2), (5β,17α)-Δ((16)(17))-20-one-pregn-2β,3β-diol 3-O-β-d-glucopyranosyl-(1 → 2)-β-d-galactopyranoside (3).

Isolation and characterization of six labdane diterpenes and one pregnane steroid of Turraeanthus africanus

Six labdane diterpene derivatives, named turraeanins F-J (3-6, 8) and epi-turraeanin J (7), and a pregnane steroid derivative named turraeasterodionene (2), were isolated by preparative high performance liquid chromatography together with thirteen known compounds from the Cameroonian medicinal plant Turraeanthus africanus. Their structures were elucidated by means of nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry in conjunction with the published data for the analogs, as well as the fragmentation patterns of each compound. Most of the known compounds were obtained for the first time from this plant. The compounds (2-7) were tested for their antibacterial efficacies against both Gram-positive and Gram-negative bacteria, including some clinically-important Risk group 2 human pathogens. Compound 4 exhibited the most pronounced antibacterial effectiveness comparable to standard reference streptomycin, with more potency against Gram-positive than Gram-negative bacteria. By comparing compounds 3, 4 and 5, a tentative structure-activity relationship could be drawn; selected oxidations at C-16 and C-18 drastically reduced the antibacterial efficacy of the parent compound (4). These results revealed the potential of compound 4 as a suitable antibacterial lead compound that might be used for further development of other derivatives to increase the antimicrobial efficacy.

Cytotoxic Cholestane and Pregnane Glycosides from Tribulus macropterus

The methanol extract of the whole parts of Tribulus macropterus Boiss. (family Zygophyllaceae) showed cytotoxic activity against a human tumour cell line (hepatocyte generation 2, HepG2) (IC50 = 2.9 μg/ml). The n-butanolic fraction obtained from successive fractionation of the methanolic extract exhibited activity against HepG2 (IC50 = 2.6 μg/ml). Therefore, this fraction was subjected to separation using different chromatographic techniques. Five compounds, 1-5, were isolated and identified as: (22S,25S)-16β,22,26-trihydroxy-cholest-4- en-3-one-16-O-β-D-glucopyranosyl-(1→3)-β-D-xylopyranoside (1), (22S,25S)-16β,22,26-trihydroxy- cholest-4-en-3-one-16-O-β-D-glucopyranosyl-(1→3)-β-d-glucopyranoside (2), sucrose (3), d-pinitol (4) and 3β-hydroxy-5α-pregn-16(17)en-20-one-3-O-β-D-xylopyranosyl-(1→2)- [β-d-xylopyranosyl-(1→3)]-β-D-glucopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-galactopyranoside (5) on the basis of spectroscopic and chemical data. The three steroidal compounds 1, 2 and 5 were also tested against the same cell line HepG2 and their IC50 values were 2.4, 2.2 and 1.1 μg/ml, respectively.

Molecular population dynamics of DNA structures in a bcl-2 promoter sequence is regulated by small molecules and the transcription factor hnRNP LL

Minute difference in free energy change of unfolding among structures in an oligonucleotide sequence can lead to a complex population equilibrium, which is rather challenging for ensemble techniques to decipher. Herein, we introduce a new method, molecular population dynamics (MPD), to describe the intricate equilibrium among non-B deoxyribonucleic acid (DNA) structures. Using mechanical unfolding in laser tweezers, we identified six DNA species in a cytosine (C)-rich bcl-2 promoter sequence. Population patterns of these species with and without a small molecule (IMC-76 or IMC-48) or the transcription factor hnRNP LL are compared to reveal the MPD of different species. With a pattern recognition algorithm, we found that IMC-48 and hnRNP LL share 80% similarity in stabilizing i-motifs with 60 s incubation. In contrast, IMC-76 demonstrates an opposite behavior, preferring flexible DNA hairpins. With 120-180 s incubation, IMC-48 and hnRNP LL destabilize i-motifs, which has been previously proposed to activate bcl-2 transcriptions. These results provide strong support, from the population equilibrium perspective, that small molecules and hnRNP LL can modulate bcl-2 transcription through interaction with i-motifs. The excellent agreement with biochemical results firmly validates the MPD analyses, which, we expect, can be widely applicable to investigate complex equilibrium of biomacromolecules.