Cytotoxic withaphysalins from the leaves of Acnistus arborescens

Withaphysalin Derivatives from Iochroma arborescens Induce Antiproliferative and Antimigratory Activities in vitro

Withanolides are steroidal lactones commonly found in plants of the Solanaceae family that have significant medicinal value. In this study, three withanolides extracted from Iochroma arborescens leaves were isolated and characterized. These included withaphysalin F (3: ) and two newly identified epimeric compounds: 18R- and 18S-O-methyl-withaphysalin F (1: and 2: ). Their structures were elucidated by NMR, IR, MS, CD, and X-ray diffraction analysis, and their potential against cell proliferation and migration was investigated. The cytotoxic assay revealed activity against different tumor and non-tumor cell lines. (18S)-O-methyl-withaphysalin F (2: ) presented cell death effects after at least 6 hours of exposure. MDA-MB-231 cells were exposed to 0.06 and 0.6 µM of (18S)-O-methyl-withaphysalin F (2: ), and reductions in cell adhesion, migration, and clonogenicity were observed. Morphological analysis revealed negative regulation in filopodia, salience, and roughness, as well as alterations in cellular microarchitecture. These results provide clues as to the effects of (18S)-O-methyl-withaphysalin F (2: ), allowing new molecular modifications to improve potency and selectivity and increase our antineoplastic arsenal.

Nephroprotective effect of Physalis peruviana L. calyx extract and its butanolic fraction against cadmium chloride toxicity in rats and molecular docking of isolated compounds

BACKGROUND

Cadmium is an environmentally toxic metal that has deleterious effects on both animals and humans due to its accumulation in different body tissues. Physalis peruviana L. fruit and calyx contain many active constituents which are used traditionally for their different biological activities. Based on the traditional uses of P. peruviana L. calyx, we aimed to evaluate the nephroprotective effect of their 80% aqueous methanol extract (AME) and n-butanol fraction (Bu.F.) against cadmium chloride-induced nephrotoxicity in rats and to correlate this activity with phytoconstituents isolated using molecular docking studies.

METHODS

The n-butanol fraction of P. peruviana L. calyx was fractionated using various chromatographic techniques and the isolated compounds were identified based on their chemical and spectroscopic data. The nephroprotective activity was assessed using cadmium chloride-induced nephrotoxicity in the rat model, by measuring some important parameters such as body weight, kidney weight, serum urea, and creatinine levels, oxidative stress markers, inflammatory markers, and histopathological examinations of kidney tissue. Molecular docking studies of the isolated compounds were performed.

RESULTS

Three withanolides named 4 β-hydroxywithanolide E (1), Physalin B (2) and 3α, 14β-dihydroxywithaphysalin N (3) were isolated and identified from the n-butanol fraction of P. peruviana L calyx extract. The extract and its butanol fraction significantly improved the serum kidney function markers and tissue oxidative status including malondialdehyde (MDA), reduced glutathione (GSH) and catalase (CAT). Additionally, the extracts significantly decreased the levels of tumor necrosis factor-alpha (TNF-α) and nuclear factor kappaB (NF-κβ). Moreover, the histological changes were ameliorated by the extracts. The molecular docking study showed that the isolated compounds displayed a remarkable inhibitory activity against IκB kinase.

CONCLUSION

The AME and its butanol fraction of P. peruviana L calyx showed potential nephroprotective activity against cadmium chloride-induced nephrotoxicity which is correlated at least in part to its considerable withanolides content.

Withaphysalins from Medicinal and Edible Physalis minima and Their Anti-inflammatory Activities

Physalis minima is a medicinal and edible plant in China. In this study, 22 new withaphysalins, including a novel 1(10 → 6)abeo-14β-hydroxy one (1) and other 15 unusual 14β-hydroxy ones (3-4, 6-17, 19), were isolated from the whole herbs of P. minima together with two known analogues (23-24). Their structures were established by extensive analysis of high-resolution electrospray ionization mass spectrometry, IR, and 1D and 2D NMR spectroscopic data. Their absolute configurations were determined by electronic circular dichroism (ECD) spectra and single-crystal X-ray crystallographic analyses, together with DFT NMR calculations. All isolated compounds were evaluated for their anti-inflammatory activity via measuring the colorimetric reporter of the secreted embryonic alkaline phosphatase gene driven by an IFN-β minimal promoter fused to five copies of the NF-κB consensus transcriptional response element and three copies of the c-Rel binding site in LPS-stimulated human THP1-Dual cells. Compounds 2, 5, 6, 9, 10, 11, and 20 showed significant anti-inflammatory effects with IC₅₀ values in the range of 3.01-13.39 μM. Among them, compounds 2 and 10 showed better anti-inflammatory effects to inhibit the secretion of IL-6, IL-1β, and TNF-α in LPS-stimulated THP1-Dual cells.

Screening of plants from the Brazilian Atlantic Forest led to the identification of Athenaea velutina (Solanaceae) as a novel source of antimetastatic agents

Plant biodiversity is a source of potential natural products for the treatment of many diseases. One of the ways of discovering new drugs is through the cytotoxic screening of extract libraries. The present study evaluated 196 extracts prepared by maceration of Brazilian Atlantic Forest trees with organic solvents and distilled water for cytotoxic and antimetastatic activity. The MTT assay was used to screen the extract activity in MCF-7, HepG2 and B16F10 cancer cells. The highest cytotoxic extract had antimetastatic activity, as determined in in vitro assays and melanoma murine model. The organic extract of the leaves of Athenaea velutina (EAv) significantly inhibited migration, adhesion, invasion and cell colony formation in B16F10 cells. The phenolic compounds and flavonoids in EAv were identified for the first time, using flow injection with electrospray negative ionization-ion trap tandem mass spectrometry analysis (FIA-ESI-IT-MSn ). EAv markedly suppressed the development of pulmonary melanomas following the intravenous injection of melanoma cells to C57BL/6 mice. Stereological analysis of the spleen cross-sections showed enlargement of the red pulp area after EAv treatment, which indicated the activation of the haematopoietic system. The treatment of melanoma-bearing mice with EAv did not result in liver damage. In conclusion, these findings suggest that A velutina is a source of natural products with potent antimetastatic activity.

Isolation and characterization of cytotoxic withanolides from the calyx of Physalis alkekengi L. var franchetii

Phytochemical investigation into the calyx of Physalis alkekengi L. var franchetii (Mast) Makino resulted in the isolation of ten cytotoxic withanolides, including five new withanolides, 1-5. Compounds 2-4 were obtained as epimeric withaphysalins. The new structures were elucidated by extensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. The withanolides were evaluated for their cytotoxic activities against the A549 and K562 cell lines. Compounds 1 and 8 exhibited potent cytotoxic activity against both cell lines with IC₅₀ values of 1.9-4.3 μM and induced typical apoptosis as evaluated by flow cytometric analysis. Further studies indicated that 1 and 8 displayed antitumour effects by suppressing the PI3K-Akt-mTOR signalling pathway.

Selective Antiproliferative Withanolides from Species in the Genera Eriolarynx and Deprea

Four new withanolides (2-5), together with 4β,7β,20-trihydroxy-1-oxowitha-2,5,24-trienolide (1), were isolated from the aerial parts of Eriolarynx iochromoides. The antiproliferative activity of all compounds purified from E. iochromoides together with four withaphysalins and four physangulidines isolated previously from three Deprea species were evaluated against human solid tumor cell lines. Four withanolides showed antiproliferative activity comparable in potency to cisplatin. Selectivity toward cancer cells and interaction with P-glycoprotein of the active withanolides were evaluated.

Natural products as new antimitotic compounds for anticancer drug development

Cell cycle control genes are frequently mutated in cancer cells, which usually display higher rates of proliferation than normal cells. Dysregulated mitosis leads to genomic instability, which contributes to tumor progression and aggressiveness. Many drugs that disrupt mitosis have been studied because they induce cell cycle arrest and tumor cell death. These antitumor compounds are referred to as antimitotics. Vinca alkaloids and taxanes are natural products that target microtubules and inhibit mitosis, and their derivatives are among the most commonly used drugs in cancer therapy worldwide. However, severe adverse effects such as neuropathies are frequently observed during treatment with microtubule-targeting agents. Many efforts have been directed at developing improved antimitotics with increased specificity and decreased likelihood of inducing side effects. These new drugs generally target specific components of mitotic regulation that are mainly or exclusively expressed during cell division, such as kinases, motor proteins and multiprotein complexes. Such small molecules are now in preclinical studies and clinical trials, and many are products or derivatives from natural sources. In this review, we focused on the most promising targets for the development of antimitotics and discussed the advantages and disadvantages of these targets. We also highlighted the novel natural antimitotic agents under investigation by our research group, including combretastatins, withanolides and pterocarpans, which show the potential to circumvent the main issues in antimitotic therapy.

Withanolides from leaves of cultivated Acnistus arborescens

Seven withanolides, including four previously unknown, were isolated from the acetone and ethanol extracts of cultivated specimens of Acnistus arborescens. These four compounds were identified as rel-(18R,22R)-5β,6β:18β,20-diepoxy-3β,18α-dimethoxy-4β-hydroxy-1-oxowith-24-enolide, rel-(20R,22R)-5β,6β-epoxy-4β,16α,20-trihydroxy-1-oxowitha-2,24dienolide, rel-(20R,22R)-16α-acetoxy-6α-chloro-4β,5β,20-trihydroxy-1-oxowitha-2,24-dienolide and rel-(20R,22R)-16α-acetoxy-20-hydroxy-1-oxowitha-2,5,24-trienolide. Their structures were elucidated by interpretation of spectroscopic data (1D and 2D NMR), HRESIMS experiments and comparison with published data for similar compounds. Cytotoxicity of the isolated compounds was evaluated against a panel of four tumor cell lines (HL-60, HCT-116, SF-268 and PANC-1). Withanolide D was the most active, with an IC50 value in the range of 0.3-1.7 μM, rel-(18R,22R)-5β,6β:18β,20-diepoxy-3β,18α-dimethoxy-4β-hydroxy-1-oxowith-24-enolide and rel-(20R,22R)-5β,6β-epoxy-4β,16α,20-trihydroxy-1-oxowitha-2,24dienolide were moderately active, while all the others were non-cytotoxic.

Withanolides from Physalis minima and their inhibitory effects on nitric oxide production

Six new withanolides (1-6), including two uncommon 1,10-seco withanolides (1 and 2), together with five known withanolides (7-11), were isolated from the whole plants of Physalis minima Linn.. The structures of new compounds were elucidated through spectroscopic methods, including (1)H, (13)C NMR, 2D-NMR, HRESIMS and circular dichroism (CD). Inhibitory effects of the isolates on nitric oxide (NO) production in lipopolysaccaride-activated RAW264.7 macrophages were evaluated. Compounds 2 and 5 showed strong inhibitory activities with IC50 values of 8.04 and 10.01 μM, respectively. Compounds 1, 9 and 10 exhibited moderate inhibitory activities with IC50 values from 25.54 to 43.58 μM.

Cell cycle arrest through inhibition of tubulin polymerization by withaphysalin F, a bioactive compound isolated from Acnistus arborescens

Many compounds used in the treatment of cancer possess tubulin-interacting properties that lead to mitotic arrest. Withaphysalins are potent cytotoxic compounds that are commonly found in plants belonging to the Solanaceae family, such as Acnistus arborescens; however, the cytotoxic mechanisms or molecular targets of these compounds remain unknown. Thus, the aim of this study was to evaluate the effects of whitaphysalins on cancer cell cycle progression and tubulin interaction. In this report, we show the antiproliferative activity of withaphysalin F and its effect in arresting cells in the G(2)/M phase of the cell cycle. These two effects are the result of the interference of withaphysalin F in the polymerization of microtubules. Withaphysalin F also induced DNA fragmentation, which can be related to an increase in mitochondrial membrane depolarization. These results suggest that interference of withaphysalin F in microtubule polymerization may induce cell cycle arrest in the G(2)/M phase and therefore contribute to growth inhibition of tumor cells in vitro. Taken together, these studies indicate that withaphysalin F could potentially be used as an anticancer drug.

Antifungal and cytotoxic activity of withanolides from Acnistus arborescens

Three compounds were isolated from Acnistus arborescens, a tree commonly used in South and Central America in traditional medicine against several infectious diseases, some of which are caused by fungi. Bioassay-guided fractionation of a MeOH extract of leaves, based on its anti-Pneumocystis carinii activity, led to the isolation of compounds 1-3. Mono- and bidimensional NMR analyses enabled identification of two new withanolides, (20R,22R)-5beta,6beta-epoxy-4beta,12beta,20-trihydroxy-1-oxowith-2-en-24-enolide (1) and (20R,22R)-16beta-acetoxy-3beta,4beta;5beta,6beta-diepoxy-12beta,20-dihydroxy-1-oxowith-24-enolide (2), and withanolide D (3). Antifungal activity on 13 fungi responsible for human infections (five dermatophytes, one nondermatophyte mold, six yeasts, and Pneumocystis carinii) was examined. Cytotoxicity of these compounds was also evaluated in vitro.

Toxic Chemical Compounds of the Solanaceae

The Solanaceae is comprised of some 2500 species of cosmopolitan plants, especially native to the American continent. They have great value as food, like the well-known potato, tomato and eggplants, and medicines, like species of Atropa, Withania and Physalis, but many plants of this family are toxic, and sometimes lethal to mammals, in particular to man. Some of them also produce hallucinations and perceptual changes. The toxic species of this family are characterized by the occurrence of a variety of chemical compounds, some of which are responsible for the toxicity and lethality observed after ingestion, while others are suspected to be toxic. In this review, the following toxic compounds belonging to different members of the Solanaceae family are described: Tropane alkaloids ( Atropa, Datura, Hyoscyamus, Mandragora); pyrrolidine and pyrrolic alkaloids ( Nierembergia, Physalis, Solanum); protoalkaloids ( Nierembergia); glycoalkaloids ( Lycopersicon, Solanum); nicotine ( Nicotiana); cardenolides ( Cestrum, Nierembergia); capsaicinoids ( Capsicum); kaurene-type tetracyclic diterpenes ( Cestrum); steroidal glycosides ( Cestrum, Solanum); 1,25-dihydroxyvitamin D3 and vitamin D3 ( Cestrum, Solanum, Nierembergia); and withasteroids, withanolides ( Withania), and physalins ( Physalis). Other bioactive chemical constituents of members of this family are sugar esters and lectins. Phenylpropanoids are not included in this paper.

Selective cytotoxicity of withaphysalins in myeloid leukemia cell lines versus peripheral blood mononuclear cells

Withaphysalins are C(28)-steroidal lactones structurally based on the ergostane skeleton that possess antiproliferative activity against tumor cell lines. In the present study, the antileukemic actvity of withaphysalin O (1), M (2), and N (3) isolated from Acnistus arborescens, against two leukemic cell lines, HL-60 and K562, was evaluated, and the cytotoxicity compared with the effects on peripheral blood mononuclear cells (PBMC). All tested compounds reduced the number of viable cells of the tumor cell lines after 24 h of exposure, except for compound 2 against the K562 cell line. The reduction was time-and concentration-dependent, and the IC(50) values ranged from 0.7 to 3.5 microM after 72 h of incubation. In addition to the growth inhibitory properties, the drugs decreased DNA synthesis after 24 h of drug exposure evaluated by the 5-bromo-2 -deoxyuridine incorporation method. None of the tested compounds reduced the number of PBMC (IC(50)>20 microM) after 72 h of incubation, in contrast to doxorubicin that decreased viable cells and increased non-viable cells even after 24 h of incubation. Morphological analysis of treated cells using hematoxylin/eosin staining indicated the presence of necrotic cells for all tested compounds in HL-60, confirmed by the use of acridine orange/ethidium bromide staining. In addition to necrotic cells, K562 cells showed morphological alterations consistent with apoptosis.