Activity-guided isolation of novel norwithanolides from depreasubtriflora with potential cancer chemopreventive activity

Recent Advances in the Chemistry and Therapeutic Evaluation of Naturally Occurring and Synthetic Withanolides

Natural products are a major source of biologically active compounds that make promising lead molecules for developing efficacious drug-like molecules. Natural withanolides are found in many flora and fauna, including plants, algae, and corals, that traditionally have shown multiple health benefits and are known for their anti-cancer, anti-inflammatory, anti-bacterial, anti-leishmaniasis, and many other medicinal properties. Structures of these withanolides possess a few reactive sites that can be exploited to design and synthesize more potent and safe analogs. In this review, we discuss the literature evidence related to the medicinal implications, particularly anticancer properties of natural withanolides and their synthetic analogs, and provide perspectives on the translational potential of these promising compounds.

Withaminimas A-F, six withanolides with potential anti-inflammatory activity from Physalis minima

Withaminimas A-F (1-6), six new withaphysalin-type withanolides were isolated from the aerial parts of Physalis minima L.. The structures of these compounds were elucidated through a variety of spectroscopic techniques including HR-MS, NMR, and ECD. Compound 1 belongs to rare 18-norwithanolides, and 2-3 were 13/14-secowithanolides. According to the traditional usage of P. minima, inhibitory effects on nitric oxide (NO) production in lipopolysaccaride-activated RAW264.7 macrophages were evaluated, and compounds 1-4 exhibited significant inhibitory effects with IC₅₀ values among 3.91-18.46 μmol·L^-1.

Withasteroid B from D. metel L. regulates immune responses by modulating the JAK/STAT pathway and the IL-17+ RORγt+ /IL-10+ FoxP3+ ratio

Datura metel L. is a medicinal herb that contains withasteroids and has a wide range of biological activities. We isolated seven withasteroids from the flowers of D. metel L and examined their ability to inhibit immune responses in vitro and in vivo. Among the withasteroids, withasteroid B2 exhibited the strongest inhibitory effect on immune responses comparing B2 with other isolated compounds from D. metel L., including suppressing the differentiation of CD4⁺ T cells by inhibiting the expression and production of T cell lineage-specific master regulators and cytokines and directly suppressing the cytokine-induced Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathways. In the interleukin (IL)-23-induced mouse ear model of skin disease, B2 repressed disease development by inhibiting the expression of proinflammatory mediators in murine ear skin. Moreover, B2 affected the maturation of dendritic cells (DCs) in vitro which, in turn, induced T cell differentiation with an increased regulatory T cell (T_reg ) phenotype and decreased T helper type 17 (Th17) phenotype. This study provides new evidence that B2 might ameliorate chronic inflammatory skin diseases by suppressing pathogenic CD4⁺ T cell differentiation and the IL-17⁺ retinoic-acid-receptor-related orphan receptor gamma t (RORγt)⁺ /IL-10⁺ forkhead box protein 3 (FoxP3)⁺ ratio. These findings suggest that B2 might mediate the therapeutic effects observed in psoriasis patients following treatment with D. metel L.

Bioactive new withanolides from the cultured soft coral Sinularia brassica

Continuing study of the ethyl acetate (EtOAc) extract of the cultured soft coral Sinularia brassica afforded five new withanolides, sinubrasolides H-L (1-5). The structures of the new compounds were elucidated on the basis of spectroscopic analysis. The cytotoxicities of new compounds 1-5 and a known compound sinubrasolide A (6) against the proliferation of a limited panel of cancer cell lines were assayed. The anti-inflammatory activities of compounds 1-6 were evaluated by measuring their ability to suppress N-formyl-methionyl-leucyl-phenyl-alanine/cytochalasin B (fMLP/CB)-induced superoxide anion generation and elastase release in human neutrophils.

Potential Anticancer Properties and Mechanisms of Action of Withanolides

Plant-based Ayurvedic medicine has been practiced in India for thousands of years for the treatment of a variety of disorders. They are rich sources of bioactive compounds potentially useful for prevention and treatment of cancer. Withania somnifera (commonly known as Ashwagandha in Ayurvedic medicine) is a widely used medicinal plant whose anticancer value was recognized after isolation of steroidal compounds withanolides from the leaves of this shrub. Withaferin A is the first member of withanolides to be isolated, and it is the most abundant withanolide present in W. somnifera. Its cancer-protective role has now been established using chemically induced and oncogene-driven rodent cancer models. The present review summarizes the key preclinical studies demonstrating anticancer effects of withaferin along with its molecular targets and mechanisms related to its anticancer effects. Anticancer potential of other withanolides is also discussed.

Withanolides from three species of the genus Deprea (Solanaceae). Chemotaxonomical considerations

Nine withanolides were isolated from the aerial parts of Deprea bitteriana, Depreacuyacensis, and Depreazamorae. D.bitteriana yielded two withaphysalins, D. cuyacensis gave two 13,14-seco withaphysalins, while D. zamorae yielded five physangulidines. The compounds were fully characterized by a combination of spectroscopic methods (1D and 2D NMR and MS). All compounds isolated from D.bitteriana and D. cuyacensis were obtained as epimeric mixtures at C-18. The structure of physangulidine D was confirmed by X-ray diffraction analysis. The skeletons found in this research support the chemotaxonomical position of the genus Deprea in the tribe Physalideae.

Capsisteroids A–F, withanolides from the leaves of Solanum capsicoides

A known withanolide steroid cilistol G (1) and six new withanolides, capsisteroids A–F (2–7), were isolated from the EtOAc extract of the leaves of Solanum capsicoides.

New anti-inflammatory withanolides from the leaves of Datura metel L

Nine new withanolides, named daturafolisides A-I (1-9), along with six known compounds (22R)-27-hydroxy-7α-methoxy-1-oxowitha-3,5,24-trienolide-27-O-β-d-glucopyranoside, daturataturin A, daturametelin J, daturataurin B, baimantuoluoside B, 12-deoxywithastramonolide (10-15), were isolated from the leaves of Datura metel L. The structures and absolute stereochemistry of these compounds were elucidated by means of spectroscopic methods including 1D and 2D NMR techniques, mass spectrometry and circular dichroism (CD) analyses. All isolates were evaluated for in vitro anti-inflammatory potential using LPS-stimulated RAW 264.7 murine macrophages. Among them, compounds 1, 2, 14, and 15 exhibited significant inhibition of nitrite production with values of IC50 at 20.9, 17.7, 17.8, and 18.4μM. Compounds 3, 4, 6, and 13 presented moderate inhibitory activities with values of IC50 at 59.0, 52.8, 71.2, and 53.1μM, while the rest compounds displayed weak suppressive effect.

Five withanolides from the leaves of Datura metel L. and their inhibitory effects on nitric oxide production

Four new withanolides named dmetelins A–D (compounds 1–4), along with the known compound 7α,27-dihydroxy-1-oxo-witha-2,5,24-trienolide (5) were isolated from the leaves of Datura metel L. (Solanaceae). Their structures were elucidated on the basis of detailed analysis of 1D and 2D NMR and mass spectrometry data. All the compounds were evaluated for their inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 cells. Compounds 1, 4 and 5 showed significant inhibitory activities, and compounds 2 and 3 showed moderate inhibitory activities with IC₅₀ values of 17.8, 11.6, 14.9, 33.3 and 28.6 μM, respectively.

Withanolide-based steroids from the cultured soft coral Sinularia brassica

Seven novel withanolides, sinubrasolides A-G (1-7), have been isolated from the cultured soft coral Sinularia brassica. The structures of the new metabolites were determined by extensive spectroscopic analyses, and the absolute configuration of 1 was established by X-ray crystallographic analysis. The cytotoxicities of compounds 1-7 against a limited panel of cancer cell lines also were determined.

Steroidal carboxylic acids from soft coral Paraminabea acronocephala

Three new steroidal carboxylic acids, paraminabic acids A-C (1-3) were isolated from a Formosan soft coral Paraminabea acronocephala. The structures of these compounds were established by extensive spectroscopic analysis and chemical methods. Application of the PGME method allowed the establishment of the absolute configurations at C-25 and C-24 for 1 and 2, respectively. Compound 3 showed potent cytotoxicity toward Hep3B, MDA-MB-231, MCF-7, and A-549 cancer cell lines, with IC(50) values ranging from 2.05 to 2.83 μg/mL. Compounds 2 and 3 were found to inhibit the accumulation of the pro-inflammatory iNOS protein.

Withanolides from the rhizomes of Dioscorea japonica and their cytotoxicity

Edible yams are tropical crops that serve as important staple foods in many parts of the world. The rhizome of Dioscorea japonica , well-known as "Japanese yam", is a food and medicinal source known as "San Yak" in Korea. Bioassay-guided fractionation and chemical investigation of the extract of this yam resulted in the identification of two new withanolides, named dioscorolide A (1) and dioscorolide B (2). The structures of these new compounds were determined by spectroscopic methods, including 1D and 2D nuclear magnetic resonance (NMR) techniques, high-resolution mass spectrometry (HRMS), and chemical methods. The cytotoxic activities of the isolates (1 and 2) were evaluated by determining their inhibitory effects on four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) and a human normal cell line (HUVEC) using a sulforhodamine B (SRB) bioassay. Compounds 1 and 2 showed cytotoxicity against tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) with IC(50) values ranging from 6.3 to 26.9 μM and exhibited lower activity against the normal cell line (HUVEC) with IC(50) values ranging from 27.1 to 28.8 μM, suggesting selective toxicity among tumor and normal cells.

Paraminabeolides A-F, cytotoxic and anti-inflammatory marine withanolides from the soft coral Paraminabea acronocephala

Six new withanolides, paraminabeolides A-F (1-6), along with five known compounds, minabeolides-1, -2, -4, -5, and -8 (7-11), were isolated from a Formosan soft coral, Paraminabea acronocephala. The structures of these compounds were elucidated by extensive spectroscopic analysis and chemical transformation. The absolute configuration of 4 was determined by the application of Mosher's method. Compounds 1 and 7 were cytotoxic toward Hep G2 cancer cells. Compounds 1-4 and 7-10 were found to significantly inhibit the accumulation of the pro-inflammatory iNOS protein. Compounds 7-10 also could effectively reduce the expression of COX-2 protein.

The cytoprotective role of the Keap1-Nrf2 pathway

An elaborate network of highly inducible proteins protects aerobic cells against the cumulative damaging effects of reactive oxygen intermediates and toxic electrophiles, which are the major causes of neoplastic and chronic degenerative diseases. These cytoprotective proteins share common transcriptional regulation, through the Keap1-Nrf2 pathway, which can be activated by various exogenous and endogenous small molecules (inducers). Inducers chemically react with critical cysteine residues of the sensor protein Keap1, leading to stabilisation and nuclear translocation of transcription factor Nrf2, and ultimately to coordinate enhanced expression of genes coding for cytoprotective proteins. In addition, inducers inhibit pro-inflammatory responses, and there is a linear correlation spanning more than six orders of magnitude of concentrations between inducer and anti-inflammatory activity. Genetic deletion of transcription factor Nrf2 renders cells and animals much more sensitive to the damaging effects of electrophiles, oxidants and inflammatory agents in comparison with their wild-type counterparts. Conversely, activation of the Keap1-Nrf2 pathway allows survival and adaptation under various conditions of stress and has protective effects in many animal models. Cross-talks with other signalling pathways broadens the role of the Keap1-Nrf2 pathway in determining the fate of the cell, impacting fundamental biological processes such as proliferation, apoptosis, angiogenesis and metastasis.

Photinides A-F, cytotoxic benzofuranone-derived gamma-lactones from the plant endophytic fungus Pestalotiopsis photiniae

Photinides A-F (1-6), six new unique benzofuranone-derived gamma-lactones, have been isolated from the crude extract of the plant endophytic fungus Pestalotiopsis photiniae. The structures of these compounds were elucidated primarily by NMR spectroscopy, and their absolute configurations were assigned by application of the CD excitation chirality method. Compounds 1-6 displayed modest cytotoxic effects against the human tumor cell line MDA-MB-231.

Cilistepoxide and cilistadiol, two new withanolides from Solanum sisymbiifolium

In addition to the known cilistol A, two new withanolides have been isolated from leaves and stem of Solanum sisymbiifolium, and assigned the structures 1-oxo-5,6; 22,26; 24,25-triepoxy-17,26-dihydroxyergost-2-ene and 1-oxo-22,26; 24,25-diepoxy-5,6,17,26-tetrahydroxy ergost-2-ene, namely cilistepoxide and cilistadiol.

Compounds obtained from sida acuta with the potential to induce quinone reductase and to inhibit 7,12-dimethylbenz[a]anthracene-induced preneoplastic lesions in a mouse mammary organ culture model

Activity-guided fractionation of the EtOAc-soluble extract of the whole plants of Sida acuta using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells, led to the isolation of ten active compounds of previously known structure, quindolinone (1), cryptolepinone (2), 11-methoxyquindoline (3), N-trans-feruloyltyramine (4), vomifoliol (5), loliolide (6), 4-ketopinoresinol (7), scopoletin (8), evofolin-A (9), and evofolin-B (10), along with five inactive compounds of known structure, ferulic acid, sinapic acid, syringic acid, (+/-)-syringaresinol, and vanillic acid. These isolates were identified by physical and spectral data measurement. A new derivative of quindolinone, 5,10-dimethylquindolin-11-one (1a) was synthesized and characterized spectroscopically. Of the active substances, compounds 1-3 and 1a exhibited the most potent QR activity, with observed CD (concentration required to double induction) values ranging from 0.01 to 0.12 microg/mL. Six compounds were then evaluated in a mouse mammary organ culture assay, with cryptolepinone (2), N-trans-feruloyltyramine (4), and 5,10-dimethylquindolin-11-one (1a) found to exhibit 83.3, 75.0, and 66.7% inhibition of 7,12-dimethylbenz[a]anthracene-induced preneoplastic lesions, respectively, at a dose of 10 microg/mL.