Withanolides from Jaborosa caulescens var. bipinnatifida

Withanolides 2,3-dihydrotrechonolide A (1) and 2,3-dihydro-21-hydroxytrechonolide A (2) were isolated along with two known withanolides trechonolide A (3) and jaborosalactone 39 (4) from Jaborosa caulescens var. bipinnatifida (Solanaceae). The structures of 1-2 were elucidated through 2D NMR and other spectroscopic techniques. In addition, the structure of withanolide 1 was confirmed by X-ray crystallographic analysis.

Epoxide group relationship with cytotoxicity in withanolide derivatives from Withania somnifera

Withania somnifera is one of the highly reputed medicinal plants of India. Its steroidal constituents exist in the form of two major substitution patterns, viz. withaferin A (1) and withanone (5). Withaferin A with oxidation at carbons 4, 5, and 6 is considered as an active type, especially as anticancer, whereas the withanones with oxidation at carbons 5, 6, and 7 rarely show any activity. We prepared a series of derivatives with modifications at carbons 5, 6, and 7 in ring B of these withanolides to study the role of the epoxide group towards the cytotoxic property of these bioactive steroids. We have converted withanolides into the respective thiiranes, amino alcohols and alcohols by selective reactions at the epoxide ring and were evaluated for in vitro anticancer activity against four cancer cell lines to study the structure activity relationships. The transformations of the epoxide group in withanolides of the withaferin A type showed moderate reduction in their cytotoxicity whereas the almost inactive withanones have shown some improvements in their alcohol derivatives.

Medicinal plants, human health and biodiversity: a broad review

Biodiversity contributes significantly towards human livelihood and development and thus plays a predominant role in the well being of the global population. According to WHO reports, around 80 % of the global population still relies on botanical drugs; today several medicines owe their origin to medicinal plants. Natural substances have long served as sources of therapeutic drugs, where drugs including digitalis (from foxglove), ergotamine (from contaminated rye), quinine (from cinchona), and salicylates (willow bark) can be cited as some classical examples.Drug discovery from natural sources involve a multifaceted approach combining botanical, phytochemical, biological, and molecular techniques. Accordingly, medicinal-plant-based drug discovery still remains an important area, hitherto unexplored, where a systematic search may definitely provide important leads against various pharmacological targets.Ironically, the potential benefits of plant-based medicines have led to unscientific exploitation of the natural resources, a phenomenon that is being observed globally. This decline in biodiversity is largely the result of the rise in the global population, rapid and sometimes unplanned industrialization, indiscriminate deforestation, overexploitation of natural resources, pollution, and finally global climate change.Therefore, it is of utmost importance that plant biodiversity be preserved, to provide future structural diversity and lead compounds for the sustainable development of human civilization at large. This becomes even more important for developing nations, where well-planned bioprospecting coupled with nondestructive commercialization could help in the conservation of biodiversity, ultimately benefiting mankind in the long run.Based on these findings, the present review is an attempt to update our knowledge about the diverse therapeutic application of different plant products against various pharmacological targets including cancer, human brain, cardiovascular function, microbial infection, inflammation, pain, and many more.

Withanolides with phytotoxic activity from two species of the genus Salpichroa: S. origanifolia and S. tristis var. lehmannii

Seven new withanolides, salpichrolides O-U (1-7), the known 2,3-dihydrosalpichrolide B (9), a substance not previously isolated from a natural source, and three known compounds, salpichrolide D (8), salpichrolide A (10), and salpichrolide C (11), were isolated and characterized from the aerial parts of Salpichroa origanifolia and S. tristis var. lehmannii. Compounds 1-4 and 8 have an oxygenated D ring, while compounds 5-7 and 9-11 possess a six-membered aromatic D ring. The structures of the isolated compounds were identified by analysis of their spectroscopic data including NMR and MS. Withanolides 1, 3, 8, 10, and 11 exhibited selective radicle growth inhibition toward Lactuca sativa (lettuce) at 150 and 400 ppm.

Synthesis and Cytotoxicity of Semisynthetic Withalongolide A Analogues

The natural product withaferin A exhibits potent antitumor activity and other diverse pharmacological activities. The recently discovered withalongolide A, a C-19 hydroxylated congener of withaferin A, was recently reported to possess cytotoxic activity against head and neck squamous cell carcinomas. Semisynthetic acetylated analogues of withalongolide A were shown to be considerably more cytotoxic than the parent compound. To further explore the structure-activity relationships, 20 new semisynthetic analogues of withalongolide A were synthesized and evaluated for cytotoxic activity against four different cancer cell lines. A number of derivatives were found to be more potent than the parent compound and withaferin A.

Tropine forming tropinone reductase gene from Withania somnifera (Ashwagandha): biochemical characteristics of the recombinant enzyme and novel physiological overtones of tissue-wide gene expression patterns

Withania somnifera is one of the most reputed medicinal plants of Indian systems of medicine synthesizing diverse types of secondary metabolites such as withanolides, alkaloids, withanamides etc. Present study comprises cloning and E. coli over-expression of a tropinone reductase gene (WsTR-I) from W. somnifera, and elucidation of biochemical characteristics and physiological role of tropinone reductase enzyme in tropane alkaloid biosynthesis in aerial tissues of the plant. The recombinant enzyme was demonstrated to catalyze NADPH-dependent tropinone to tropine conversion step in tropane metabolism, through TLC, GC and GC-MS-MS analyses of the reaction product. The functionally active homodimeric ∼60 kDa enzyme catalyzed the reaction in reversible manner at optimum pH 6.7. Catalytic kinetics of the enzyme favoured its forward reaction (tropine formation). Comparative 3-D models of landscape of the enzyme active site contours and tropinone binding site were also developed. Tissue-wide and ontogenic stage-wise assessment of WsTR-I transcript levels revealed constitutive expression of the gene with relatively lower abundance in berries and young leaves. The tissue profiles of WsTR-I expression matched those of tropine levels. The data suggest that, in W. somnifera, aerial tissues as well possess tropane alkaloid biosynthetic competence. In vivo feeding of U-[¹⁴C]-sucrose to orphan shoot (twigs) and [¹⁴C]-chasing revealed substantial radiolabel incorporation in tropinone and tropine, confirming the de novo synthesizing ability of the aerial tissues. This inherent independent ability heralds a conceptual novelty in the backdrop of classical view that these tissues acquire the alkaloids through transportation from roots rather than synthesis. The TR-I gene expression was found to be up-regulated on exposure to signal molecules (methyl jasmonate and salicylic acid) and on mechanical injury. The enzyme's catalytic and structural properties as well as gene expression profiles are discussed with respect to their physiological overtones.

Cytotoxic withanolides from the leaves of Moroccan Withania frutescens

CONTEXT

Withania species are a rich source of interesting phytochemical substances (withanolides) which have shown several biological properties.

OBJECTIVE

To investigate the cytotoxic potential of Withania frutescens (L.) Pauquy (Solanaceae) leaf extracts and isolated active compounds against cultured tumor cell lines.

MATERIALS AND METHODS

The crude methanol extract of W. frutescens leaves was partitioned with dichloromethane, ethyl acetate and n-butanol. MeOH extract and its fractions were tested for their cytotoxic activity against cancer cell lines (HepG2 and HT29) using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Bioassay-guided fractionation was performed for the active CH₂Cl₂ fraction employing column chromatography and preparative high-performance liquid chromatography. Structural elucidation of the isolated active compounds was carried out mainly by 1D and 2D NMR and mass spectrometry. The compounds were then tested for their cytotoxic activity.

RESULTS

The CH₂Cl₂ fraction was the most active against HT29 cell line. The fractionation procedure resulted in the isolation of 4β,17α,27-trihydroxy-1-oxo-22-R-witha-2,5,24-trienolide (1), 5β,6β-epoxy-4β,17α,27-trihydroxy-1-oxowitha-2,24-dienolide (2) and 2,3-dihydroxywithaferin A-3β-O-sulfate (3). The latter exhibited the strongest cytotoxic activity against HT29 cancer cell lines (IC₅₀ of 1.78 ± 0.09 µM) which was comparable to that of 5-fluorouracil (5-FU) used as the positive antimitotic control.

DISCUSSION AND CONCLUSION

Compounds 2 and 3 were isolated from W. frutescens for the first time. Data obtained suggest that the sulfated steroidal lactone (3) can be considered as a compound with potential application in the new anticancer drugs development field.

Overexpression of WsSGTL1 gene of Withania somnifera enhances salt tolerance, heat tolerance and cold acclimation ability in transgenic Arabidopsis plants

Background

Sterol glycosyltrnasferases (SGT) are enzymes that glycosylate sterols which play important role in plant adaptation to stress and are medicinally important in plants like Withania somnifera. The present study aims to find the role of WsSGTL1 which is a sterol glycosyltransferase from W. somnifera, in plant’s adaptation to abiotic stress.

Methodology

The WsSGTL1 gene was transformed in Arabidopsis thaliana through Agrobacterium mediated transformation, using the binary vector pBI121, by floral dip method. The phenotypic and physiological parameters like germination, root length, shoot weight, relative electrolyte conductivity, MDA content, SOD levels, relative electrolyte leakage and chlorophyll measurements were compared between transgenic and wild type Arabidopsis plants under different abiotic stresses - salt, heat and cold. Biochemical analysis was done by HPLC-TLC and radiolabelled enzyme assay. The promoter of the WsSGTL1 gene was cloned by using Genome Walker kit (Clontech, USA) and the 3D structures were predicted by using Discovery Studio Ver. 2.5.

Results

The WsSGTL1 transgenic plants were confirmed to be single copy by Southern and homozygous by segregation analysis. As compared to WT, the transgenic plants showed better germination, salt tolerance, heat and cold tolerance. The level of the transgene WsSGTL1 was elevated in heat, cold and salt stress along with other marker genes such as HSP70, HSP90, RD29, SOS3 and LEA4-5. Biochemical analysis showed the formation of sterol glycosides and increase in enzyme activity. When the promoter of WsSGTL1 gene was cloned from W. somnifera and sequenced, it contained stress responsive elements. Bioinformatics analysis of the 3D structure of the WsSGTL1 protein showed functional similarity with sterol glycosyltransferase AtSGT of A. thaliana.

Conclusions

Transformation of WsSGTL1 gene in A. thaliana conferred abiotic stress tolerance. The promoter of the gene in W.somnifera was found to have stress responsive elements. The 3D structure showed functional similarity with sterol glycosyltransferases.

Anticancer steroids: linking natural and semi-synthetic compounds

Steroids, a widespread class of natural organic compounds occurring in animals, plants and fungi, have shown great therapeutic value for a broad array of pathologies. The present overview is focused on the anticancer activity of steroids, which is very representative of a rich structural molecular diversity and ability to interact with various biological targets and pathways. This review encompasses the most relevant discoveries on steroid anticancer drugs and leads through the last decade and comprises 668 references.

Efficient genetic transformation of Withania coagulans (Stocks) Dunal mediated by Agrobacterium tumefaciens from leaf explants of in vitro multiple shoot culture

An efficient and reproducible Agrobacterium-mediated genetic transformation of Withania coagulans was achieved using leaf explants of in vitro multiple shoot culture. The Agrobacterium strain LBA4404 harboring the binary vector pIG121Hm containing β-glucuronidase gene (gusA) under the control of CaMV35S promoter was used in the development of transformation protocol. The optimal conditions for the Agrobacterium-mediated transformation of W. coagulans were found to be the co-cultivation of leaf explants for 20 min to agrobacterial inoculum (O.D. 0.4) followed by 3 days of co-cultivation on medium supplemented with 100 μM acetosyringone. Shoot bud induction as well as differentiation occurred on Murashige and Skoog medium supplemented with 10.0 μM 6-benzylaminopurine, 8.0 μM indole 3-acetic acid, and 50.0 mgl(-1) kanamycin after three consecutive cycles of selection. Elongated shoots were rooted using a two-step procedure involving root induction in a medium containing 2.5 μM indole 3-butyric acid for 1 week and then transferred to hormone free one-half MS basal for 2 weeks. We were successful in achieving 100 % frequency of transient GUS expression with 5 % stable transformation efficiency using optimized conditions. PCR analysis of T0 transgenic plants showed the presence of gusA and nptII genes confirming the transgenic event. Histochemical GUS expression was observed in the putative transgenic W. coagulans plants. Thin layer chromatography showed the presence of similar type of withanolides in the transgenic and non-transgenic regenerated plants. A. tumefaciens mediated transformation system via leaf explants developed in this study will be useful for pathway manipulation using metabolic engineering for bioactive withanolides in W. coagulans, an important medicinal plant.

Two novel norwithasteroids with unusual six- and seven-membered ether rings in side chain from flos daturae

Chemical investigation of 50% ethanol eluate fraction of macroporous resin for the flower of Datura metel L. collected in Jiangsu province of China resulted in the isolation of two novel naturally occurring norwithasteroids, baimantuoluoline I (1) and baimantuoluoside J (2). Their structures were elucidated as 5 α , 6 β , 12 β -trihydroxy-1-oxo-2-en-ergosta-21,24;22,29-diepoxy-26-carboxylic acid (1) and 5 α , 6 β , 12 β , 25-tetrahydroxy-1-oxo-2-en-ergosta-21,24;22,29-diepoxy-26-carboxylic acid (2) on the basis of extensive spectroscopic analysis, including 1D, 2D-NMR, and HR-ESI-MS. According to the literatures, this study represents the first report of the norwithasteroids in the side chain with unusual six- and seven-membered ether rings instead of those with an unmodified skeleton (δ-lactone or δ-lactol side chain) and a modified skeleton ( γ -lactone or γ -lactol side chain) in the family of withanolides. Meanwhile, compounds 1 and 2 were evaluated for their immunosuppressive activity against mice splenocyte proliferation in vitro.

Antiproliferative withanolides from Datura wrightii

A new withanolide, named withawrightolide (1), and four known withanolides (2-5) were isolated from the aerial parts of Datura wrightii. The structure of compound 1 was elucidated through 2D NMR and other spectroscopic techniques. In addition, the structure of withametelin L (2) was confirmed by X-ray crystallographic analysis. Using MTS viability assays, withanolides 1-5 showed antiproliferative activities against human glioblastoma (U251 and U87), head and neck squamous cell carcinoma (MDA-1986), and normal fetal lung fibroblast (MRC-5) cells with IC50 values in the range between 0.56 and 5.6 μM.

Minor withanolides of Physalis longifolia: structure and cytotoxicity

In our recent publication on bioactive guided isolation of compounds from Physalis longifolia (Solanaceae) novel anti-proliferative agents withalongolides A (4) and B (5), and their highly cytotoxic analogues, withalongolide A 4,19,27-triacetate (4a) and withalongolide B 4,19-diacetate (5a) were elucidated. In this study, the two lead compounds (4, 5) were re-isolated in gram quantities for the purpose of further analogue preparation and in vivo testing that would continue to probe structure-activity relationships. During this process, two additional withanolides, named withalongolides O (1) and P (2), were elucidated. Their structures were determined by spectroscopic techniques with 1 being subsequently confirmed by X-ray crystallographic analysis. Utilizing a MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] viability assay, withalongolide O (1) and its 4,7-diaceatate (1a), both containing the functionalities of Δ(2)-1-oxo- in A ring, a 5β,6β-epoxy in B ring, and a lactone ring in the nine-carbon side chain, exhibited potent cytotoxicity against human head and neck squamous cell carcinoma (JMAR and MDA-1986), melanoma (B16F10 and SKMEL-28), and normal fetal lung fibroblast (MRC-5) cells with IC(50) values in the range between 0.15 and 2.95 µM. In addition, the previously reported α orientation of 7-acetate group in acnistins C and D should be revised to the β orientation on the basis of NMR data comparison.

Leishmanicidal active withanolides from a pakistani medicinal plant, Withania coagulans

In the course of screening for leishmanicidal constituents from Asian and South American medicinal plants, a Pakistani medicinal plant, Withania coagulans, showed activity. We therefore studied the active components of the methanol extract of aerial parts of W. coagulans. From the ethyl acetate soluble fraction of the extract, four new withanolides (1-4) were isolated along with seven known withanolides (5-11). The new compounds were elucidated to be (14R,15R,17S,20S,22R)-14,15,17,20-tetrahydroxy-1-oxowitha-2,5,24-trienolide (1), (14R,15R,17S,20S,22R)-14,15,17,20-tetrahydroxy-1-oxowitha-3,5,24-trienolide (2), (14S,17R,20S,22R)-14,17,20-trihydroxy-1-oxowitha-2,5,24-trienolide (3), and (14S,17R,20S,22R)-14,17,20-trihydroxy-1-oxowitha-3,5,24-trienolide (4), from 1H-NMR, 13C-NMR, 2D-NMR and high resolution (HR)-MS data. Some of these compounds having the partial structure 1-oxo-2,5-diene showed strong leishmanicidal activity against Leishmania major.

The genetic architecture of a complex ecological trait: host plant use in the specialist moth, Heliothis subflexa

We used genetic mapping to examine the genetic architecture of differences in host plant use between two species of noctuid moths, Heliothis subflexa, a specialist on Physalis spp., and its close relative, the broad generalist H. virescens. We introgressed H. subflexa chromosomes into the H. virescens background and analyzed 1462 backcross insects. The effects of H. subflexa-origin chromosomes were small when measured as the percent variation explained in backcross populations (0.2-5%), but were larger when considered in relation to the interspecific difference explained (1.5-165%). Most significant chromosomes had effects on more than one trait, and their effects varied between years, sexes, and genetic backgrounds. Different chromosomes could produce similar phenotypes, suggesting that the same trait might be controlled by different chromosomes in different backcross populations. It appears that many loci of small effect contribute to the use of Physalis by H. subflexa. We hypothesize that behavioral changes may have paved the way for physiological adaptation to Physalis by the generalist ancestor of H. subflexa and H. virescens.

Withaferin A-related steroids from Withania aristata exhibit potent antiproliferative activity by inducing apoptosis in human tumor cells

Six new withanolides (1-6) along with eleven known ones (7-17) were isolated from the leaves of Withania aristata. Their structures were elucidated on the basis of spectroscopic analysis, including 1D and 2D NMR techniques. Semisynthesis of the minority metabolites 7 and 15 from compounds 6 and 9, respectively, as starting material, was performed. The isolated compounds as well as three derivatives (7a, 9a and 9b) of withaferin A were evaluated for cytotoxicity against HeLa (carcinoma of the cervix), A-549 (lung carcinoma) and MCF-7 (breast adenocarcinoma) human cancer cell lines, and against normal Vero cells (African green monkey kidney). Five compounds from this series (8, 9a, 9b, 11 and 13) exhibited potent antiproliferative effects on the tumor cells, even higher than the well known anticancer agent, withaferin A (9). Phosphatidylserine externalization, chromatin condensation, and caspase-3 activation clearly indicated apoptosis as a mechanism of action. The structure-activity relationship revealed valuable information on the pharmacophore for withanolide-type compounds.

Withanolides-induced breast cancer cell death is correlated with their ability to inhibit heat protein 90

Withanolides are a large group of steroidal lactones found in Solanaceae plants that exhibit potential anticancer activities. We have previously demonstrated that a withanolide, tubocapsenolide A, induced cycle arrest and apoptosis in human breast cancer cells, which was associated with the inhibition of heat shock protein 90 (Hsp90). To investigate whether other withanolides are also capable of inhibiting Hsp90 and to analyze the structure-activity relationships, nine withanolides with different structural properties were tested in human breast cancer cells MDA-MB-231 and MCF-7 in the present study. Our data show that the 2,3-unsaturated double bond-containing withanolides inhibited Hsp90 function, as evidenced by selective depletion of Hsp90 client proteins and induction of Hsp70. The inhibitory effect of the withanolides on Hsp90 chaperone activity was further confirmed using in vivo heat shock luciferase activity recovery assays. Importantly, Hsp90 inhibition by the withanolides was correlated with their ability to induce cancer cell death. In addition, the withanolides reduced constitutive NF-κB activation by depleting IκB kinase complex (IKK) through inhibition of Hsp90. In estrogen receptor (ER)-positive MCF-7 cells, the withanolides also reduced the expression of ER, and this may be partly due to Hsp90 inhibition. Taken together, our results suggest that Hsp90 inhibition is a general feature of cytotoxic withanolides and plays an important role in their anticancer activity.

Antiproliferative activity of withanolide derivatives from Jaborosa cabrerae and Jaborosa reflexa. Chemotaxonomic considerations

Three withanolides were isolated from the aerial parts of Jaborosa reflexa Phil. Jaborosa cabrerae Barboza yielded five sativolide withanolides (including jaborosalactones R, S, 38, and 39) and two trechonolide withanolides epimeric at C-23 (trechonolide A and jaborosalactone 32). In addition, five derivatives were obtained by chemical derivatization of jaborosalactone 38, and all compounds were fully characterized by 1D and 2D NMR spectroscopic studies. The in vitro antiproliferative activities of the major natural withanolides and the semisynthetic derivatives were examined against HBL-100, HeLa, SW1573, T-47D, and WiDr human solid tumor cancer cell lines. Some chemotaxonomic considerations are discussed.

Physangulidines A, B, and C: three new antiproliferative withanolides from Physalis angulata L

Bioassay-directed fractionation of the whole plant of Physalis angulata L. afforded three new antiproliferative withanolides with an unusual carbon framework: physangulidines A (1), B (2), and C (3). Structures of the three isomeric withanolides were determined by a combination of HRMS, NMR spectroscopic, and X-ray crystallographic methods. Each has shown significant antiproliferative activity against DU145 prostate cancer cells. Physangulidine A (1) was further tested against a wide range of additional cancer cell lines and found to exhibit significant antiproliferative activity.

Anti-proliferative withanolides from the Solanaceae: a structure-activity study

As part of our search for bioactive compounds from plant biodiversity, 29 withanolides (1, 3-6, 9, 12-18, and 20-35) were recently isolated from three members of the Solanaceae: Physalis longifolia, Vassobia breviflora, and Withania somnifera. Six derivatives (2, 7, 8, 10, 11, and 19) were prepared from these naturally occurring withanolides. All compounds (1-35) were evaluated for in vitro anti-proliferative activity against an array of cell lines [melanoma cell lines (B16F10, SKMEL28); human head and neck squamous cell carcinomas (HNSCC) cell lines (JMAR, MDA1986, DR081-1); breast cancer cell line (Hs578T), and non-malignant human cell line (MRC5)]. This led to the discovery of 15 withanolides, with IC50 values in the range of 0.067-17.4 µM, including withaferin A 1, withaferin A 4,27-diacetate 2, 27-O-glucopyranosylwithaferin A 3, withalongolide H 4, withalongolide C 5, withalongolide A 6, withalongolide A 4,27-diacetate 7, withalongolide A 4,19,27-triacetate 8, withalongolide B 9, withalongolide B 4-acetate 10, withalongolide B 4,19-diacetate 11, withalongolide D 16, withalongolide E 17, withalongolide G 21, and 2,3-dihydrowithaferin A 3-O-sulfate 22). In order to update the growing literature on withanolides and their activities, we summarized the distribution, structural types and anti-proliferative activities for all published withanolides to date. The structure-activity relationship analysis (SARA) confirmed the importance of the presence of a Δ2-1-oxo- functionality in ring A, a 5β,6β-epoxy or 5α-chloro-6β-hydroxy groupings in ring B, and nine carbon side chain with a lactone moiety for cytotoxic activity. Conversely, the SARA indicated that the -OH or -OR groups at C-4, 7, 11, 12, 14, 15, 16, 17, 18, 19, 20, 23, 24, 27, 28 were not contributors to the observed anti-proliferative activity within the systems analyzed.

Cytotoxic withanolide constituents of Physalis longifolia

Fourteen new withanolides, 1-14, named withalongolides A-N, respectively, were isolated from the aerial parts of Physalis longifolia together with eight known compounds (15-22). The structures of compounds 1-14 were elucidated through spectroscopic techniques and chemical methods. In addition, the structures of withanolides 1, 2, 3, and 6 were confirmed by X-ray crystallographic analysis. Using a MTS viability assay, eight withanolides (1, 2, 3, 7, 8, 15, 16, and 19) and four acetylated derivatives (1a, 1b, 2a, and 2b) showed potent cytotoxicity against human head and neck squamous cell carcinoma (JMAR and MDA-1986), melanoma (B16F10 and SKMEL-28), and normal fetal fibroblast (MRC-5) cells with IC₅₀ values in the range between 0.067 and 9.3 μM.