Steroids from the Meliaceae family and their biological activities

Steroids are farnesyl diphosphate-derived triterpene derivatives widely distributed in Meliaceae plants that can have several health benefits due to their biological activities. This literature survey on chemical and pharmacological studies of steroids from the Meliaceae plants indicates that 157 distinct steroids classified into six subclasses including (in decreasing number): pregnane-, stigmastane-, ergostane-, cholestane-, androstane- and ecdysterone-type steroids have been reported from a total of 49 plant species. This review aims to provide a reference document compiling information about the occurrence, chemistry and biological activities of meliaceous steroids for the period from 1988 to July 2023. In particular, generalities about the chemistry of steroids with unusual skeletons and underlying biosynthetic pathways are highlighted. In addition, some structural relationships between different compound types and their biological activities are presented. The information used during the writing of this paper was collected from the online libraries PubMed, Google Scholar and Scifinder using the keywords steroids and Meliaceae with no language restriction. This review points out new avenues for further investigations of steroids from plants of the Meliaceae family.

In Silico and In Vitro Screening of Some Pregnane Glycosides Isolated from Certain Caralluma Species as SARS-COV-2 Main Protease Inhibitors

SARS-CoV-2 caused pandemic represented a major risk for the worldwide human health, animal health and economy, forcing extraordinary efforts to discover drugs for its prevention and cure. Considering the extensive interest in the pregnane glycosides because of their diverse structures and excellent biological activities, we investigated them as antiviral agents against SARS-COV-2. We selected 21 pregnane glycosides previously isolated from the genus Caralluma from Asclepiadaceae family to be tested through virtual screening molecular docking simulations for their potential inhibition of SARS-CoV-2 Mpro. Almost all target compounds showed a more or equally negative docking energy score relative to the co-crystallized inhibitor X77 (S=-12.53 kcal/mol) with docking score range of (-12.55 to -19.76 kcal/mol) and so with a potent predicted binding affinity to the target enzyme. The activity of the most promising candidates was validated by in vitro testing. Arabincoside C showed the highest activity (IC50=35.42 μg/ml) and the highest selectivity index (SI=9.9) followed by Russelioside B (IC50=50.80 μg/ml), and Arabincoside B (IC50=53.31 μg/ml).

Hexagonosides A-F: Pregnane glycosides isolated from Caralluma hexagona

Chemical investigation of Caralluma hexagona Lavranos, a wild plant growing in Yemen, led to the isolation of four previously undescribed acylated pregnane glycosides, hexagonosides A-D (1-4), together with two sets of mixtures (hexagonosides E and F), each set consists of three interconvertible pregnane glycoside isomers, hexagonosides E (5a-c) and F (6a-c). The chemical structures of the isolated pregnane glycosides were elucidated by extensive 1D/2D NMR and HRESI-MS analysis, featuring 6'-O-benzoyl-1'-O-β-glucosyl residue at aglycone C-20; while aglycone C-3 was substituted with disaccharide sugar chain (1, 2, 5a-c) or a trisaccharide sugar chain (3, 4, 6a-c). Metabolites E and F included an extra benzoyl substitution in C-20 glucosyl residue which is migrating between the OH groups of C-2', C-3' and C-4' resulting in equilibrating conformations (5a-c and 6a-c) when incubated in HPLC solvent, which we confirmed by the analytical study.

Two new pregnane glycosides from the root of Cynanchum auriculatum

Two new pregnane glycosides (1 and 2), together with four known ones (3- 6), were isolated from the roots of Cynanchum auriculatum Royle ex Wight (Asclepiadaceae). On the basis of detailed spectroscopic analysis and chemical method, the structures of new compounds were characterized to be metaplexigenin 3-O-β-D-cymaropyranosyl- (1→4)-α-L-diginopyranosyl-(1→4)-β-D-cymaropyranoside (1), metaplexigenin 3-O-α-L-diginopyranosyl-(1→4)-β-D-cymaropyranoside (2). All the isolated compounds (1-6) were tested for their in vitro inhibitory activity against the growth of human colon cancer cell lines HCT-116. Compounds 5 and 6 showed significant cytoxicities with IC50 values of 43.58 µM and 52.21 µM.

Cynanotophyllosides E-F, two minor pregnane glycosides from the roots of cultivated Cynanchum otophyllum

Cynanotophyllosides E-F, two new minor pregnane glycosides were isolated from the antidepressant active fraction of cultivated Cynanchum otophyllum, and their structures were determined as 12-O-vanilloyl-deacetylmetaplexigenin 3-O-β -D-glucopyranosyl-(1→4)-β -D-glucopyranosyl-(1→4)-β -D-cymaropyranosyl-(1→4)-β -D-oleandropyranosyl-(1→4)-β -D-digitoxopyranoside, and 12-O-nicotinoyl-deacetylmetaplexigenin 3-O-β -D-glucopyranosyl-(1→4)-β -D-glucopyranosyl-(1→4)-β -D-cymaropyranosyl-(1→4)-β -D-oleandropyranosyl-(1→4)-β -D-cymaropyranoside respectively, with the combination of spectroscopic and chemical analysis.

Cytotoxic steroids from the stems of Strophanthus divaricatus

Phytochemical investigation on the stems of Strophanthus divaricatus led to the isolation of four undescribed cardiac glycosides and one undescribed C₂₁ pregnane, together with eleven known steroids. Their structures were elucidated by a comprehensive analysis of HRESIMS, 1D and 2D NMR spectra. The absolute configuration of 16 was determined by comparison of the experimental and computed ECD spectra. Compounds 1-13 and 15 displayed potent to significant cytotoxicity against human cancer cell lines K562, SGC-7901, A549 and HeLa with IC₅₀ values of 0.02-16.08, 0.04-23.13, 0.06-22.31 and 0.06-15.13 μM, respectively.

Nine New Pregnane Glycosides from the Cultivated Medicinal Plant Marsdenia tenacissima

The ethnobotanical plant Marsdenia tenacissima has been used for hundreds of years for Dai people in Yunnan Province, China. Previously, chemical investigations on this plant have revealed that pregnane glycosides were the main biological constituents. Nine new pregnane glycosides, marsdeosides A–I (1–9), were isolated from cultivated dried stems of the medicinal plant Marsdenia tenacissima in this study. The structures were analyzed by extensive spectroscopic analysis, including 1D, 2D NMR, HRESIMS, and IR spectroscopic analysis. The absolute configurations of the sugar moieties were identified by comparing the Rf values and specific optical rotations with those of the commercially available standard samples and the data reported in the literature. Marsdeosides A (1) featured an unusual 8,14-seco-pregnane skeleton. Compounds 1, 8, and 9 showed activity against nitric oxide production in lipopolysaccharide-activated macrophage RAW264.7, with IC50 values of 37.5, 38.8, and 42.8 μM (L-NMMA was used as a positive control, IC50 39.3 μM), respectively. This study puts the knowledge of the chemical profile of the botanical plant M. tenacissima one step forward and, thereby, promotes the sustainable utilization of the resources of traditional folk medicinal plants.

Six C21 steroidal glycosides from Cynanchum wallichii Wight roots and their multidrug resistance reversal activities

Six unidentified C21 steroidal glycosides, cynwallosides A-F, as well as twenty-two known compounds, were isolated from the roots of Cynanchum wallichii Wight. The structures of cynwallosides A-F were determined by spectroscopic analysis and acidic hydrolysis. Most of these twenty-eight compounds were found to significantly reverse drug resistance in both the MCF-7/ADR and HepG2/ADM cell lines by suppressing P-gp protein expression. Further investigation revealed that three compounds suppressed P-gp expression by significantly inactivating the JNK and NF-κB pathways.

C21 Steroidal Glycosides from the Roots of Oxypetalum caeruleum

The MeOH extract from dried roots of Oxypetalum caeruleum (Apocynaceae) plants yielded seventeen new pregnane glycosides, some of which had the acylated-ramanone or -isoramanone type aglycone. The structures of these compounds were established using NMR, MS spectroscopic analysis and chemical evidence.

Trichilones A-E: New Limonoids from Trichilia adolfi

In addition to the trichilianones A-D recently reported from Trichilia adolfi, a continuing investigation of the chemical constituents of the ethanol extract of the bark of this medicinal plant yielded the five new limonoids 1-5. They are characterized by having four fused rings and are new examples of prieurianin-type limonoids, having a ε-lactone which in 4 and 5 is α, β- unsaturated. The structures of the isolated metabolites were determined by high field NMR spectroscopy and HR mass spectrometry. The new metabolites were shown to have the ε-lactone fused with a tetrahydrofuran ring which is connected to an oxidized hexane ring joined with a cyclo-pentanone having a 3-furanyl substituent. As the crude extract possesses antileishmanial activity, the compounds were assayed for cytotoxic and antiparasitic activities in vitro in murine macrophage cells (raw 264.7 cells) and in Leishmania amazoniensis as well as L. braziliensis promastigotes. Metabolites 1-3 and 5 showed moderate cytotoxicity (between 30-94 µg/mL) but are not responsible for the antileishmanial effect of the extract.

Russelioside B; A pregnane glycoside for treatment of gastric ulcer via modulation of heat shock protein-70 and vascular endothelial growth factor

Gastric ulcers are a very common public health problem affecting up to 10% worldwide. Russelioside B is a steroidal glycoside isolated from several Caralluma species. No study tested the ulcer healing potential of the compound. The current study aimed to assess the protective effect of russelioside B against ethanol-induced gastric mucosal injury in rats. Ulcer was induced on rats by a single intragastric dose of absolute ethanol (5 mL/kg). Rats were randomly assorted into four groups (n = 8) and given treatments (Antodine, 20 mg/kg or russelioside B, 50 mg/kg) by oral gavage 1 h before ulcer induction. Pretreatment with russelioside B (50 mg/kg) attenuated the gastric mucosal injury as proved by a decrease of ulcer index, and histological scores. It suppressed the gastric inflammation by a significant lowering the tumor necrosis factor-α and interleukin-6 levels with myeloperoxidase activity (which are also aggravating factors in the case of Covid-19 infection). In addition, administration of russelioside B halted the gastric oxidative stress via inhibition of lipid peroxides by maintaining reduced glutathione and by decreasing malondialdehyde. It was able also to restore the sharp drop in the levels of heat shock protein-70, vascular endothelial growth factor and prostaglandin E2 induced by ethanol. Additionally, it showed carbonic anhydrase inhibition activity. The gastroprotective action of russelioside B was umpired through multi mechanistic actions; suppression of gastric oxidative stress, inflammation, anti-apoptotic activities and enhanced gastric mucosal protection by up-regulation of endothelial growth factor, normalization of heat shock protein-70 and prostaglandin E2. These actions were comparable in part to some classical antiulcer drugs such as Antodine.

Epigynumgenane-type pregnane glycosides from Epigynum cochinchinensis and their immunosuppressive activity

Five undescribed C₂₁ pregnane glycosides, epigycosides D-H, together with four known analogues, two lignans, and a flavonoid have been isolated from the stems of Epigynum cochinchinensis. The structures of pregnane glycosides were elucidated using spectroscopic techniques and acid hydrolysis. The in vitro immunological activities were assessed against Con A-stimulated proliferation of mice splenocytes. The C₂₁ pregnane glycosides showed immunosuppressive activity in a concentration-dependent manner. Moreover, epigycoside E exhibited a potent immunosuppressive effect, and the IC₅₀ value on Con A-stimulated mice splenocytes was 22.1 ± 6.4 μM. Epigycoside E also caused G₀/G₁ arrest, and inhibited TNF-α and IL-2 production.

Molecular rearrangements of poststerone derivative steroid core with formation of unique D-homostructures of pregnane and androstane series

20R-Hydroxy short-chain ecdysteroids were synthesized by chemo- and stereoselective reduction of poststerone acetonide with L-Selectride or LiAlH₄. The same reaction with the excess of L- Selectride followed by the treatment of the reaction mixture with hydrochloric acid is accompanied by (8R)-13(14 → 8)abeo- rearrangements, which resulted in the contraction/expansion of C/D pregnane rings. The reaction of 20R-hydroxy poststerone analogs with (diethylamino)sulfur trifluoride (DAST) proceeds through intramolecular rearrangements and provides D-homo- or 13,14-seco- androstane structures.

Cytotoxic Pregnane Steroidal Glycosides from Chonemorpha megacalyx

Three new C₂₁ pregnane steroids, chonemorphols A-C (1, 3, and 4), 11 new C₂₁ steroidal glycosides, chonemorphosides A-K (2 and 5-14), and 11 known compounds (15-25) were obtained from the vines and leaves of Chonemorpha megacalyx Pierre. Their structures were established using extensive spectroscopic data. The X-ray crystallographic data of 1 and 3 permitted definition of their absolute configurations. Notably, 1 and 2 possessed an uncommon 6/5/6/5/5-fused steroidal ring system. Compound 7 displayed significant cytotoxicity against several cancer cell lines with IC₅₀ values of 2.0-3.6 μM.

A new highly oxygenated pregnane and two new 5-hydroxymethylfurfural derivatives from the water decoction of Poria cocos

A new highly oxygenated pregnane steroid, pregn-7-ene-2β,3α,15α,20-tetrol (1) and two new 5-hydroxymethylfurfural derivatives, (5-formylfuran-2-yl)methyl 2-hydroxypropanoate (2) and (5-formylfuran-2-yl)methyl 2-(4-hydroxyphenyl)acetate (3), together with four known compounds, were isolated from the water decoction of Poria cocos. Their structures were established on the basis of extensive spectroscopic analysis. Compound 1 showed moderate inhibitory activity and a known compound (3S,6S)-3-[(1R)-1-hydroxyethyl]-6-(phenylmethyl)-2,5-piperazinedione (5) showed weak inhibitory activity against α-glucosidase, respectively.

New Sweet-Tasting C21 Pregnane Glycosides from the Roots of Myriopteron extensum

To investigate the sweet-tasting components in the roots of Myriopteron extensum, the phytochemical study of its roots was conducted, which led to the discovery of 12 new C21 pregnane glycosides (extensumside M-X, 1-12) and two known ones (extensumside C and extensumside E, 13-14). Their chemical structure elucidation was accomplished by means of spectroscopic methods: IR, UV, ESI-MS, and NMR (¹H NMR, ¹³C NMR, HSQC, ¹H-¹H COSY, HMBC, HSQC-TOCSY, and ROESY), as well as the chemical evidence. Sensory analysis of these compounds revealed that nine of them (1, 3, 4, 5, 6, 7, 8, 13, and 14) are highly sweet-tasting compounds. Their sweetness intensities are 25 to 400 times greater than that of sucrose. Analysis of the structure-activity relationship (SAR) indicated that the sweet intensities of the isolated compounds are closely related to the aglycone 3β,16α-dihydroxy-pregn-5-en-20-one, the number and type of the monosaccharide in the sugar chain linked to C-3 and C-16 and the position of the mBe group.

Aestivalosides A-L, twelve pregnane glycosides from the seeds of Adonis aestivalis

Eight adonilide (14,20α-epoxy-3β,20-dihydroxy-14β-pregn-5-en-18-oic acid γ-lactone) glycosides, named aestivalosides A-H, and four glycosides of the adonilide derivatives, named aestivalosides I-L, were isolated from the MeOH extract of seeds of Adonis aestivalis. Aestivalosides A-L were previously undescribed compounds, and were structurally characterized using spectroscopic techniques, including two-dimensional NMR, and chemical methods.

Rapid structure prediction by HPLC-ESI-MSn of twenty-five polyoxypregnane tetraglycosides from Dregea sinensis with NMR confirmation of eight structures

Dregea sinensis Hemsl is an important herbal medicine in the Dai nationality of China. Its prominent clinical application has generated interest in the polyoxypregnane glycosides of the plant. This paper describes an extension of previous research on the polyoxypregnane di- and triglycosides of D. sinensis, aiming at identifying related tetraglycosides. On the basis of HPLC-ESI-MSⁿ analysis in positive mode, twenty-five previously undescribed polyoxypregnane tetraglycosides were characterized (regarding molecular masses and fragmentation in MSⁿ) from an ethyl acetate fraction that was not previously investigated. Guided by MSⁿ fragmentation and known structures of related di- and triglycosides from D. sinensis, tentative structures were predicted from the MS data. In order to test the predictions, eight of the glycosides were isolated and their structures were elucidated by 1D and 2D NMR methods, confirming the tentative predictions. Finally, the cytotoxicity of the isolates was evaluated on several human cell lines with little effect in general, even though slight inhibitory effects of four polyoxypregnane glycosides were detected at 10 μM against the human leukemia cell line HL-60.

New 8,12;8,20-diepoxy-8,14-secopregnane hexa- and hepta-glycosides from the roots of Asclepias tuberosa

Previously, phytochemical investigation of the roots of Asclepias tuberosa (Asclepiadaceae) led to the isolation of some 8,12;8,20-diepoxy-8,14-secopregnane tri-, tetra-, and penta-glycosides. An additional eight new minor 8,12;8,20-diepoxy-8,14-secopregnane glycosides were afforded in the recent investigation of this plant. These glycosides consisted of six or seven 2,6-dideoxy-hexopyranoses together with the aglycone, tuberogenin. The structures of each of these compounds were established using NMR, mass spectroscopic analysis and chemical evidence. As 8,12;8,20-diepoxy-8,14-secopregnane-type glycosides were observed only in A. tuberosa, these compounds were considered to be characteristic phytochemicals of this plant.

Pregnane glycosides from Cynanchum menarandrense

Five new pregnane-type steroidal glycosides, named menarandrosides A-E (1-2, 5-7) were isolated from the aerial parts of Cynanchum menarandrense, together with three known compounds, carumbelloside I (3), carumbelloside II (4), and pregnenolone-3-O-gentiobioside (8). Their structures were determined on the basis of spectroscopic analyses including NMR and mass spectrometry, reporting C-21 steroids glycosylated only by one or two glucose moieties. Compounds were then investigated for their potential to stimulate glucagon-like peptide-1 (GLP-1) secretion in intestinal cells; although none of the pure compounds had any influence, the fraction enriched in pregnanes exhibited a significant activity, suggesting a possible synergistic effect. Furthermore, none of the purified compounds affected cell viability.

C21 steroidal glycosides from Cynanchum auriculatum and their neuroprotective effects against H2O2-induced damage in PC12 cells

Twenty-three undescribed previously C₂₁ steroidal glycosides, named saccatols D-K and cynsaccatols I-W, together with six known analogs were isolated from the roots of Cynanchum auriculatum Royle ex Wight (Apocynaceae). Their structures were elucidated by a variety of spectroscopic techniques, as well as HRESIMS and GC method. All isolated compounds were tested their neuroprotective effects on the model of H₂O₂-induced damage to PC12 cells. Except saccatols D-F, J, cynsaccatol V and wilfoside A, other twenty-three isolates produced significantly activities against H₂O₂-induced cell damage (P < 0.001). Furthermore, cynsaccatols I, N, O and S can obvious inhibition of damaged PC12 cell apoptosis at their dosages of 1 μM by Annexin V-FITC/PI double staining assay with flow cytometry.

Anti-inflammatory 12,20-Epoxypregnane and 11,12-seco-Pregnane Glycosides from the Stems of Hoya kerrii

Five 12,20-epoxypregnane glycosides (1-3, 5, and 6) and two 11,12-seco-pregnane glycosides (4 and 7) with spirodilactone motifs, as well as spirodilactone cleavage products 8 and 9, were isolated from the stems of Hoya kerrii. The relative configurations of the three related skeletons were supported by ROESY experiments and X-ray crystallographic analyses. The isolates were evaluated for their anti-inflammatory activity based on the inhibition of NO production in RAW264.7 cells, and some showed IC₅₀ values ranging from 12.6 to 96.5 μM. The most potent compound, 9a, was also examined for its anti-inflammatory mechanism against mRNA expression and was found to down-regulate mRNA expression of iNOS and COX-2 in a dose-dependent manner.

14,15-Secopregnane-type C21-steriosides from the roots of Cynanchum stauntonii

Nine 14,15-secopregnane-type C₂₁-steriosides, stauntosides U, V, V₁-V₃, W and C₁-C₃, as well as two known C₂₁-steriosides, were isolated from the roots of Cynanchum stauntonii. Stauntosides U, V and V₁-V₃ share the same basic structural features of 8α:14α,14:16,15:20,18:20-tetraepoxy-14,15-secopregn-6-ene-3β,5α,9α-triol, with the numbering system following that of C₂₁-pregnanes. The aglycones of stauntosides U, V and V₁-V₃ are classified into two subcategories, the 5,9-dihydroxy groups and 5α:9α-peroxy bridge, according to the oxidative states of the two hydroxy groups at the C-5 and C-9 positions. The anti-inflammatory activity of the major compounds was assessed in an in vitro inflammatory model of mouse peritoneal macrophages using IC₅₀ values of the inhibition of nitric oxide (NO) production as an indicator. Stauntosides V₁ and V₃ exhibited target activity with IC₅₀ values of 9.3 μM and 12.4 μM, respectively, compared with dexamethasone, which was used as a positive control.

Sugar-free pregnane-type steroids from the roots of Cynanchum stauntonii

Two new sugar-free 14,15-secopregnane-type steroids, 14-O-methyl-3-epi-hirundigenin (1) and 2-deoxyamplexicogenin A (2), along with two known sugar-free pregnane-type steroids, were isolated from the 95% ethanol extract of the roots of Cynanchum stauntonii. The structures of the new compounds were characterized on the basis of extensive spectroscopic analyses, mainly 1D and 2D NMR methods, albeit the MS experiments did not display the molecular ion peaks. Compound 2 was the aglycones of stauntosides J and K, etc., previously isolated from C. stauntonii. The isolation and identification of the new compounds graced the structural diversity of pregnane-type steroids from C. stauntonii.

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.

Antitumor metastasis pregnane alkaloids from Pachysandra terminalis

Three new pregnane alkaloids, named terminamines H-J (1-3), together with two known alkaloids (4 and 5), were isolated from the ethanol extract of Pachysandra terminalis. The structures of isolated compounds were elucidated by spectroscopic methods, including (1)H and (13)C NMR, 2D NMR, and HR-ESI-MS. Compounds 1, 4, and 5 revealed significant anti-metastasis activities. In addition, compound 1 inhibited the expression of p-PKCζ in MDA-MB-231 cells, and compound 4 inhibited the expressions of p-PKCζ in MDA-MB-231 and A549 cells.