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

The role of silicon in drug discovery: a review

This review aims to highlight the role of silicon in drug discovery. Silicon and carbon are often regarded as being similar with silicon located directly beneath carbon in the same group in the periodic table. That being noted, in many instances a clear dichotomy also exists between silicon and carbon, and these differences often lead to vastly different physiochemical and biological properties. As a result, the utility of silicon in drug discovery has attracted significant attention and has grown rapidly over the past decade. This review showcases some recent advances in synthetic organosilicon chemistry and examples of the ways in which silicon has been employed in the drug-discovery field.

Withania frutescens (L.) Pauquy, a valuable Mediterranean shrub containing bioactive withanolides

The bushy plant Withania frutescens (L.) Pauquy is well distributed in the West-Mediterranean area, notably in the south of Spain, Algeria and Morocco where is it is used traditionally for the treatment of various human diseases, including diabetes. Unlike the two major species W. somnifera and W. coagulans extensively studied, the genomically close species W. frutescens has been much less investigated. Nevertheless, this shrub species displays a comparable phytochemical profile and marked antioxidant and anti-inflammatory properties, at the origin of reported pharmacological effects and its traditional uses. Here we have analyzed the diversity of biological effects reported with leaves and root extracts of W. frutescens. Hydroalcoholic extracts prepared from the aerial parts of the plant have revealed antihyperglycemic and cell-protective activities along with antimicrobial and anticorrosive effects. The extracts contained diverse polyphenolic compounds and a few alkaloids (calystegines) but most of the observed effects have been attributed to the presence of withanolides which are modified C28 ergostane-type steroids. Our analysis focused in part on specific withanolides found in W. frutescens, in particular an unusual 3-O-sulfated withanolide considered as a potential pro-drug of the major active compound withaferin A (WA) and a lead compound for the development of a potential drug candidate. The mechanism of action of this sulfated WA analogue is discussed. Altogether, our unprecedented extensive analysis of W. frutescens highlighted the pharmacological potential of this atypical medicinal plant. By analogy with the major cultivated Withania species, the market potential of little-known plant is underlined.

Naturally Occurring Norsteroids and Their Design and Pharmaceutical Application

The main focus of this review is to introduce readers to the fascinating class of lipid molecules known as norsteroids, exploring their distribution across various biotopes and their biological activities. The review provides an in-depth analysis of various modified steroids, including A, B, C, and D-norsteroids, each characterized by distinct structural alterations. These modifications, which range from the removal of specific methyl groups to changes in the steroid core, result in unique molecular architectures that significantly impact their biological activity and therapeutic potential. The discussion on A, B, C, and D-norsteroids sheds light on their unique configurations and how these structural modifications influence their pharmacological properties. The review also presents examples from natural sources that produce a diverse array of steroids with distinct structures, including the aforementioned A, B, C, and D-nor variants. These compounds are sourced from marine organisms like sponges, soft corals, and starfish, as well as terrestrial entities such as plants, fungi, and bacteria. The exploration of these steroids encompasses their biosynthesis, ecological significance, and potential medical applications, highlighting a crucial area of interest in pharmacology and natural product chemistry. The review emphasizes the importance of researching these steroids for drug development, particularly in addressing diseases where conventional medications are inadequate or for conditions lacking sufficient therapeutic options. Examples of norsteroid synthesis are provided to illustrate the practical applications of this research.

A Homodimer of Withaferin A Formed by Base-Promoted Elimination of Acetic Acid from 27-O-Acetylwithaferin A Followed by a Diels-Alder Reaction

Treatment of 27-O-acetylwithaferin A (2) with the non-nucleophilic base, 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), afforded 5β,6β-epoxy-4β-hydroxy-1-oxo-witha-2(3),23(24),25(27)-trienolide (3) and 4, a homodimer of withaferin A resulting from a Diels-Alder [4 + 2] type cycloaddition of the intermediate α,β-dimethylene-δ-lactone (9). Structures of 3 and 4 were elucidated using HRMS and 1D and 2D NMR spectroscopic data. The structure of 4 was also confirmed by single crystal X-ray crystallographic analysis of its bis-4-O-p-nitrobenzoate (8). Formation of withaferin A homodimer (4) as the major product suggests regio- and stereoselectivity of the Diels-Alder [4 + 2] cycloaddition reaction of 9. Acetylation of 2-4 afforded their acetyl derivatives 5-7, respectively. Compounds 2-4 and 6-8 were evaluated for their cytotoxic activities against four prostate cancer (PC) cell lines (LNCaP, 22Rv1, DU-145, and PC-3) and normal human foreskin fibroblast (HFF) cells. Significantly, 4 exhibited improved activity compared to the other compounds for most of the tested cell lines.

Withanolides: Promising candidates for cancer therapy

Natural products have played a significant role throughout history in the prevention and treatment of numerous diseases, particularly cancers. As a natural product primarily derived from various medicinal plants in the Withania genus, withanolides have been shown in several studies to exhibit potential activities in cancer treatment. Consequently, understanding the molecular mechanism of withanolides could herald the discovery of new anticancer agents. Withanolides have been studied widely, especially in the last 20 years, and attracted the attention of numerous researchers. Currently, over 1200 withanolides have been classified, with approximately a quarter of them having been reported in the literature to be able to modulate the survival and death of cancer cells through multiple avenues. To what extent, though, has the anticancer effects of these compounds been studied? How far are they from being developed into clinical drugs? What are their potential, characteristic features, and challenges? In this review, we elaborate on the current knowledge of natural compounds belonging to this class and provide an overview of their natural sources, anticancer activity, mechanism of action, molecular targets, and implications for anticancer drug research. In addition, direct targets and clinical research to guide the design and implementation of future preclinical and clinical studies to accelerate the application of withanolides have been highlighted.

Antibacterial activity of withanolides and their structure-activity relationship

Two new withanolides, (17R,20S,22R)-4β-acetoxy-5β,6β-epoxy-19,27-dihydroxy-1-oxo-witha-2,24-dienolide (withalongolide A 4-acetate (5) and (17R,20S,22R)-5β,6β-epoxy-27-hydroxy-1,4-dioxo-witha-24-enolide (9), and seven known withanolides with normal structure (1-4, 6-8) were isolated from aerial parts of Cuatresia colombiana. Several semisynthetic derivatives were prepared from the natural metabolites withaferin A and jaborosalactone 38. The compounds were fully characterized by a combination of spectroscopic methods (1D and 2D NMR and MS). The compounds isolated from C. colombiana, sixteen withanolides previously isolated from different Solanaceae species with different skeletons and semisynthetic derivatives were evaluated for their antibacterial activity against a selected panel of Gram-positive and Gram-negative bacteria. According to the bioactivity against S. aureus and E. faecalis, the compounds evaluated were divided into three groups: compounds with high activity (MIC 0.063 mM), compounds with moderate activity (0.5 mM > MIC > 0.125 mM) and non-active compounds (MIC ≥1 mM); in addition, some structure-activity relationship keys could be inferred.

Withaferin A: A Dietary Supplement with Promising Potential as an Anti-Tumor Therapeutic for Cancer Treatment - Pharmacology and Mechanisms

Cancer, as the leading cause of death worldwide, poses a serious threat to human health, making the development of effective tumor treatments a significant challenge. Natural products continue to serve as crucial resources for drug discovery. Among them, Withaferin A (WA), the most active phytocompound extracted from the renowned dietary supplement Withania somnifera (L.) Dunal, exhibits remarkable anti-tumor efficacy. In this manuscript, we aim to comprehensively summarize the pharmacological characteristics of WA as a potential anti-tumor drug candidate, with the objective of contributing to its further development and the discovery of prospective drugs. Through an extensive review of literature from PubMed, Science Direct, and Web of Science, we have gathered substantial evidence showcasing WA's significant anti-tumor effects against a wide range of cancers in both in vitro and in vivo studies. Mechanistically, WA exerts its anti-tumor influence by inducing cell cycle arrest, apoptosis, autophagy, and ferroptosis. Additionally, it inhibits cell proliferation, cancer stem cells, tumor metastasis, and also suppresses epithelial-mesenchymal transition (EMT) and angiogenesis. Several studies have identified direct target proteins of WA, such as vimentin, Hsp90, annexin II and mFAM72A, while BCR-ABL, Mortalin (mtHsp70), Nrf2, and c-MYB are potential targets of WA. Notwithstanding its remarkable anti-tumor efficacy, there are some limitations associated with WA, including potential toxicity and poor oral bioavailability, which need to be addressed when considering it as an anti-tumor candidate agent. Nevertheless, I given its promising anti-tumor attributes, WA remains an encouraging candidate for future drug development. Unveiling the exact target and comprehensive mechanism of WA's action represents a crucial research direction to pursue in the future.

Multi-target withaferin-A analogues as promising anti-kinetoplastid agents through the programmed cell death

Leishmaniasis and Chagas disease, two of the most prevalent neglected tropical diseases, are a world health problem. The harsh reality of these infective diseases is the absence of effective and safe therapies. In this framework, natural products play an important role in overcoming the current need to development new antiparasitic agents. The present study reports the synthesis, antikinetoplastid screening, mechanism study of fourteen withaferin A derivatives (2-15). Nine of them (2-6, 8-10 and 12) showed a potent dose-dependent inhibitory effect on the proliferation of Leishmania amazonensis and L. donovani promastigotes and Trypanosoma cruzi epimastigotes with IC₅₀ values ranging from 0.19 to 24.01 µM. Outstandingly, the fully acetylated derivative 10 (4,27-diacetylwithaferin A) was the most potent compound showing IC₅₀ values of 0.36, 2.82 and 0.19 µM against L. amazonensis, L. donovani and T. cruzi, respectively. Furthermore, analogue 10 exhibited approximately 18 and 36-fold greater antikinetoplastid activity, on L. amazonensis and T. cruzi, than the reference drugs. The activity was accompanied by significantly lower cytotoxicity on the murine macrophage cell line. Moreover, compounds 2, 3, 5-7, 9 and 10 showed more potent activity than the reference drug against the intracellular amastigotes forms of L. amazonensis and T.cruzi, with a good selectivity index on a mammalian cell line. In addition, withaferin A analogues 3, 5-7, 9 and 10 induce programmed cell death through a process of apoptosis-like and autophagy. These results strengthen the anti-parasitic potential of withaferin A-related steroids against neglected tropical diseases caused by Leishmania spp. and T. cruzi parasites.

Antifungal Potential of Canarian Plant Extracts against High-Risk Phytopathogens

Phytopathogens are responsible for great losses in agriculture. In particular, Fusarium, Alternaria and Botrytis are fungal diseases that affect crops worldwide. In the search for eco-friendly solutions to pest control, plants and their chemo-biodiversity are promising sources of biopesticides for integrated pest management. The aim of the present study is to report the evaluation of sixteen plant species from the Canary Islands Archipelago against the phytopathogenic fungi Botrytis cinerea, Fusarium oxysporum, and Alternaria alternata. The plants were selected on the basis of their traditional uses in medicine and/or pest control, as well as on scientific studies reporting their uses in crop protection. Their growth inhibition (% I), in an in vitro test-assay on mycelium, was used to identify six ethanolic plant extracts displaying activity (% I > 30% at 1 mg/mL) against at least one of the assayed fungi. The most effective plant extracts were further fractionated by liquid−liquid partition, using solvents of increasing polarity. This procedure led to an improvement of the bioactivity against the phytopathogens, even affecting the hexane fraction from S. canariensis and achieving an 83.93% of growth inhibition at 0.5 mg/mL on B. cinerea. These findings identified five plant-derived extracts as potential candidates for the future development of new biofungicides, which could be applied in integrated pest management.

Withaferin A: From Ancient Remedy to Potential Drug Candidate

Withaferin A (WA) is a pivotal withanolide that has conquered a conspicuous place in research, owning to its multidimensional biological properties. It is an abundant constituent in Withania somnifera Dunal. (Ashwagandha, WS) that is one of the prehistoric pivotal remedies in Ayurveda. This article reviews the literature about the pharmacological profile of WA with special emphasis on its anticancer aspect. We reviewed research publications concerning WA through four databases and provided a descriptive analysis of literature without statistical or qualitative analysis. WA has been found as an effective remedy with multifaceted mechanisms and a broad spectrum of pharmacological profiles. It has anticancer, anti-inflammatory, antiherpetic, antifibrotic, antiplatelet, profibrinolytic, immunosuppressive, antipigmentation, antileishmanial, and healing potentials. Evidence for wide pharmacological actions of WA has been established by both in vivo and in vitro studies. Further, the scientific literature accentuates the role of WA harboring a variable therapeutic spectrum for integrative cancer chemoprevention and cure. WA is a modern drug from traditional medicine that is necessary to be advanced to clinical trials for advocating its utility as a commercial drug.

Natural withanolides, an update

Covering: March 2010 to December 2020. Previous review: Nat. Prod. Rep., 2011, 28, 705This review summarizes the latest progress and perspectives on the structural classification, biological activities and mechanisms, metabolism and pharmacokinetic investigations, biosynthesis, chemical synthesis and structural modifications, as well as future research directions of the promising natural withanolides. The literature from March 2010 to December 2020 is reviewed, and 287 references are cited.

Evaluation of the geroprotective effects of withaferin A in Drosophila melanogaster

Withanolides are a class of compounds usually found in plant extracts which are an attractive geroprotective drug design starting point. We evaluated the geroprotective properties of Withaferin A (WA) in vivo using the Drosophila model. Flies were supplemented by nutrient medium with WA (at a concentration of 1, 10, or 100 μM dissolved in ethanol) for the experiment group and 30 μM of ethanol for the control group. WA treatment at 10 and 100 μM concentrations prolong the median life span of D. melanogaster's male by 7.7, 9.6% (respectively) and the maximum life span (the age of death 90% of individuals) by 11.1% both. Also WA treatment at 1, 10 and 100 μM improved the intestinal barrier permeability in older flies and affected an expression of genes involved in antioxidant defense (PrxV), recognition of DNA damage (Gadd45), heat shock proteins (Hsp68, Hsp83), and repair of double-strand breaks (Ku80). WA was also shown to have a multidirectional effect on the resistance of flies to the prooxidant paraquat (oxidative stress) and 33° C hyperthermia (heat shock). WA treatment increased the resistance to oxidative stress in males at 4 and 7 week old and decreased it at 6 weeks old. It increased the male's resistance to hyperthermia at 2, 4 and 7 weeks old and decreased it at 3, 5 and 8 weeks old. WA treatment decreased the resistance to hyperthermia in females at 1, 2 and 3 weeks old and not affected on their resistance to oxidative stress.

Withanolide-Type Steroids from Withania aristata as Potential Anti-Leukemic Agents

Leukemia is a blood or bone marrow cancer with increasing incidence in developed regions of the world. Currently, there is an ongoing need for novel and safe anti-leukemic agents, as no fully effective chemotherapy is available to treat this life-threatening disease. Herein, are reported the isolation, structural elucidation, and anti-leukemic evaluation of twenty-nine withanolide-type steroids (1-29) from Withania aristata. Among them, the new isolated withanolides, withaperoxidins A-D (1-4) have an unusual six-membered cyclic peroxide moiety on the withasteroid skeleton as a structural novelty. Their structures have been elucidated by means of spectroscopic analyses, including 2D NMR experiments. In addition, extensive structure-activity relationships and in silico ADME studies were employed to understand the pharmacophore and pharmacokinetic properties of this series of withasteroids. Compounds 15, 16, and 22 together with withaferin A (14) were identified as having improved antiproliferative effect (IC50 ranging from 0.2 to 0.7 μM) on human leukemia HL-60 cell lines compared with the reference drug, etoposide. This cytotoxic potency was also coupled with good selectivity index (SI 33.0-9.2) on non-tumoral Vero cell line and in silico drug likeness. These findings revealed that these natural withasteroids are potential candidates as chemotherapeutic agents in the treatment of leukemia.

Effect of Withania Somnifera on the antioxidant and neurotransmitter status in sleep deprivation induced Wistar rats

Sleep is normally a period of relaxation and repair, important for the maintenance of physiological homeostasis and psychological balance. "Globally, millions of people experiences sleep deprivation daily". Sleep deprivation (SD) impairs cognitive functions, decreases anti-oxidative defense and induces neuronal changes. Withania somnifera (WS), commonly known as an "Indian Ginseng" has broad therapeutic applications, including anti-inflammatory activities, actions on immune system, circulatory system, central nervous system etc., The study is aimed to assess effect of Withania somnifera on antioxidant status and neurotransmitter level in sleep deprivation induced male Wistar albino rats. The study was done in the Department of Physiology, Meenakshi Medical College and Hospital, Enathur, Kanchipuram. 24 male adult Wistar rats weighing 120-150g were used for the study. They were divided into 4 groups with 6 animals in each group. (Group I - cage control, Group II - large platform control, Group III - sleep deprived group and Group IV - WS treated SD group). Animals were deprived sleep for one week using a modified multiple platform method. Oxidative stress parameters and antioxidant enzymes were measured using spectrophotometry. Neurotransmitters such as dopamine and serotonin concentration in the serum were measured by ELISA method. There was a marked (by one-way ANOVA test) decrease observed in the antioxidants enzymes in the cortex of both large platform control and sleep deprivation induced group. The group treated with W. somnifera root extract significantly reduced the free radical production and lipid peroxidation with simultaneous increase in the level of antioxidant enzymes compared to the untreated group. Also in our study the concentration of dopamine and serotonin was found to be significantly reduced (p < 0.05) in sleep deprived (SD) and large platform control group when compared to cage control group. Whereas the group treated with W. somnifera (400mg/kg b.wt) increased the neurotransmitter levels significantly. Withania somnifera proved to be an effective therapeutic agent by maintaining the antioxidant status and neurotransmitter levels.

Identification of bioactive molecule from Withania somnifera (Ashwagandha) as SARS-CoV-2 main protease inhibitor

SARS-CoV-2 is the causative agent of COVID-19 and has been declared as pandemic disease by World Health Organization. Lack of targeted therapeutics and vaccines for COVID-2019 have triggered the scientific community to develop new vaccines or drugs against this novel virus. Many synthetic compounds and antimalarial drugs are undergoing clinical trials. The traditional medical practitioners widely use Indian medicinal plant Withania somnifera (Ashwagandha) natural constituents, called withanolides for curing various diseases. The main protease (M^pro) of SARS-CoV-2 plays a vital role in disease propagation by processing the polyproteins which are required for its replication. Hence, it denotes a significant target for drug discovery. In the present study, we evaluate the potential of 40 natural chemical constituents of Ashwagandha to explore a possible inhibitor against main protease of SARS-CoV-2 by adopting the computational approach. The docking study revealed that four constituents of Ashwagandha; Withanoside II (-11.30 Kcal/mol), Withanoside IV (-11.02 Kcal/mol), Withanoside V (-8.96 Kcal/mol) and Sitoindoside IX (-8.37 Kcal/mol) exhibited the highest docking energy among the selected natural constituents. Further, MD simulation study of 100 ns predicts Withanoside V possess strong binding affinity and hydrogen-bonding interactions with the protein active site and indicates its stability in the active site. The binding free energy score also correlates with the highest score of -87.01 ± 5.01 Kcal/mol as compared to other selected compounds. In conclusion, our study suggests that Withanoside V in Ashwagandha may be serve as a potential inhibitor against M^pro of SARS-CoV-2 to combat COVID-19 and may have an antiviral effect on nCoV.Communicated by Ramaswamy H. Sarma.

Withanolides from Withania aristata as Antikinetoplastid Agents through Induction of Programmed Cell Death

Leishmaniasis and American trypanosomiasis are parasitic diseases that cause significant clinical, social and economic impact on the population of tropical and subtropical countries. Their current treatment is limited and presents multiple drawbacks, including high toxicity, high cost, lengthy treatment plans, as well as the emergence of resistant species. Therefore, there is a need to find new lead compounds with high potency against parasites and low toxicity in patients. In the present work, the bioguided fractionation of an endemic plant from the Canary Islands, Withania aristata, led to the identification of withanolide-type metabolites (1-3) with leishmanicidal and trypanocidal activities. Compounds 1 and 3 showed a significant dose-dependent inhibition effect on the proliferation of L. amazonensis promastigotes and T. cruzi epimastigotes, higher than the reference drugs, miltefosine and benznidazole, respectively. Moreover, compounds 1-3 were more potent (IC₅₀ 0.055-0.663 µM) than the reference drug against the intracellular amastigote stage of L. amazonensis, with a high selectivity index on murine macrophage cells (SI 58.66-216.73). Studies on the mechanism of death showed that the compounds induced programmed cell death or that which was apoptosis-like. The present findings underline the potential of withanolides as novel therapeutic antikinetoplastid agents.

Expanding the Chemical Space of Withaferin A by Incorporating Silicon To Improve Its Clinical Potential on Human Ovarian Carcinoma Cells

Ovarian cancer represents the seventh most commonly diagnosed cancer worldwide. Herein, we report on the development of a withaferin A (WA)-silyl ether library with 30 analogues reported for the first time. Cytotoxicity assays on human epithelial ovarian carcinoma cisplatin-sensitive and -resistant cell lines identified eight analogues displaying nanomolar potency (IC₅₀ ranging from 1 to 32 nM), higher than that of the lead compound and reference drug. This cytotoxic potency is also coupled with a good selectivity index on a nontumoral cell line. Cell cycle analysis of two potent analogues revealed cell death by apoptosis without indication of cell cycle arrest in G0/G1 phase. The structure-activity relationship and in silico absorption, distribution, metabolism, and excretion studies demonstrated that the incorporation of silicon and a carbonyl group at C-4 in the WA framework enhances potency, selectivity, and drug likeness. These findings reveal analogues 22, 23, and 25 as potential candidates for clinical translation in patients with relapsed ovarian cancer.

Viwithan, a Standardized Withania somnifera Root Extract Induces Apoptosis in Murine Melanoma Cells

Background:

Withania somnifera is an Indian medicinal herb known for the multipotential ability to cure various therapeutic ailments as described in the ayurvedic system of medicine.

Objective:

In the present study, we have evaluated the antiproliferative activity of a standardized W. somnifera root extract (Viwithan) against different human and murine cancer cell lines.

Materials and Methods:

The cytotoxicity of Viwithan was determined using thiazolyl blue tetrazolium blue assay and crystal violet staining. The apoptotic changes in B16F1 cells following treatment with Viwithan were observed by acridine orange/ethidium bromide (AO/EB) staining and DNA fragmentation assay. The binding affinity of withanolides in Viwithan with antiapoptotic proteins B-cell lymphoma 2, B-cell lymphoma-extra large, and myeloid cell leukemia 1 (MCL-1) were studied using in silico approach.

Results:

The half maximal inhibitory concentration (IC50) values of Viwithan against liver hepatocellular carcinoma, Henrietta Lacks cervical carcinoma cells, human colorectal carcinoma cell line, and Ehrlich ascites carcinoma cells were 1830, 968, 2715, and 633 μg/ml, respectively. Interestingly, Viwithan was highly effective against B16F1 cells with an IC50 value of 220 μg/ml after 24 h treatment. The morphological alterations of apoptotic cell death were clearly observed in the AO/EB-stained cells after treatment with Viwithan. Viwithan induced late apoptotic changes in treated B16F1 cells as evident by the ladder formation of fragmented DNA in a time-dependent manner. The findings of molecular docking showed that withanolides present in Viwithan have a more binding affinity with the antiapoptotic proteins, particularly MCL-1.

Conclusion:

We have reported for the first time that Viwithan with 5% withanolides has a potent cytotoxic effect, particularly against B16F1 murine melanoma cells among the different cancer cell lines tested.

SUMMARY

The present study reports for the first time that Viwithan, a standardized 5% Withania somnifera root extract, has potent cytotoxicity against B16F1 murine melanoma cells

We have investigated the in vitro cytotoxicity of Viwithan in different human and murine cancer cells. Interestingly, we found that Viwithan was particularly very effective against B16F1 melanoma cells with a half maximal inhibitory concentration value of 220 μg/ml

The microscopic observations following acridine orange/ethidium bromide staining and DNA fragmentation assays clearly indicated that Viwithan might initiate late apoptosis in B16F1 cells

The binding affinity of withanolides in Viwithan with antiapoptotic proteins of B-cell lymphoma 2 family was predicted using AutoDock tool. The results from in silico studies indicated a plausible synergistic effect of withanolides attributing to the Viwithan-induced apoptosis through suppression of intrinsic pathway for carcinogenesis.

Abbreviations used: MTT: Thiazolyl blue tetrazolium blue; DMSO: Dimethyl sulfoxide; BSA: Bovine serum albumin; DMEM: Dulbecco's minimum essential medium; NCCS: National Centre for Cell Science; PBS: Phosphate-Buffered Saline; HepG2: Liver hepatocellular carcinoma; HeLa: Henrietta Lacks cervical carcinoma cells; HCT-116: Human colorectal carcinoma cell line; EAC: Ehrlich ascites carcinoma cells; IC50: Half maximal inhibitory concentration; AO/EB: Acridine orange/Ethidium bromide; BCL-2: B-cell lymphoma 2; BCL-XL: B-cell lymphoma-extra large; MCL-1: Myeloid cell leukemia 1; PDB: Protein Data Bank; ANOVA: Analysis of variance.

Lauric acid and myristic acid from Allium sativum inhibit the growth of Mycobacterium tuberculosis H37Ra: in silico analysis reveals possible binding to protein kinase B

CONTEXT

The bulb of Allium sativum Linn (Alliaceae) has numerous medicinal values. Though the petroleum ether extract of the bulb has shown to exhibit antimycobacterial activity, the phytochemical(s) responsible for this inhibitory activity is not known.

OBJECTIVE

To characterize the bioactive compounds in the petroleum ether extract of Allium sativum (garlic) that inhibit the growth of Mycobacterium tuberculosis H37Ra.

MATERIALS AND METHODS

Bioactivity-guided fractionation was employed to isolate the bioactive compounds. Antimycobacterial activity was evaluated by well-diffusion method and microplate alamar blue assay (MABA). Infrared spectroscopy, mass spectrometry and nuclear magnetic resonance spectroscopy were used to characterize the bioactive compounds. Autodock was used to obtain information on molecular recognition, and molecular dynamics simulation was performed using GROMACS.

RESULTS

The bioactive compounds that inhibited the growth of M. tuberculosis H37Ra were found to be lauric acid (LA) and myristic acid (MA). The minimal inhibitory concentration of LA and MA was found to be 22.2 and 66.7 μg/mL, respectively. In silico analysis revealed that these fatty acids could bind at the cleft between the N-terminal and C-terminal lobes of the cytosolic domain of serine/threonine protein kinase B (PknB).

DISCUSSION AND CONCLUSION

The inhibition activity was dependent on the alkyl chain length of the fatty acid, and the amino acid residues involved in binding to fatty acid was found to be conserved across the Pkn family of proteins. The study indicates the possibility of using fatty acid derivatives, involving Pkn family of proteins, to inhibit the signal transduction processes in M. tuberculosis.

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.

Anticancer activities of Withania somnifera: Current research, formulations, and future perspectives

CONTEXT

Cancer, being a cause of death for major fraction of population worldwide, is one of the most studied diseases and is being investigated for the development of new technologies and more accurate therapies. Still the currently available therapies for cancer have many lacunae which affect the patient's health severely in the form of side effects. The natural drugs obtained from the medicinal plants provide a better alternative to fight against this devastating disease. Withania somnifera L. Dunal (Solanaceae), a well-known Ayurvedic medicinal plant, has been traditionally used to cure various ailments for centuries.

OBJECTIVES

Considering the immense potential of W. somnifera, this review provides a detail account of its vital phytoconstituents and summarizes the present status of the research carried out on its anticancerous activities, giving future directions.

METHODS

The sources of scientific literature were accessed from various electronic databases such as PubMed, Google Scholar, Science Direct, and library search.

RESULTS

Various parts of W. somnifera especially the roots with its unique contents have been proved effective against different kinds of cancers. The most active components withanolides and withaferins along with a few other metabolites including withanone (WN) and withanosides have been reported effective against different types of cancer cell lines.

CONCLUSION

This herb holds an important place among various anticancer medicinal plants. It is very essential to further screen and to investigate different formulations for anticancer therapy in vitro as well as in vivo in combination with established chemotherapy.

Withanolide E sensitizes renal carcinoma cells to TRAIL-induced apoptosis by increasing cFLIP degradation

Withanolide E, a steroidal lactone from Physalis peruviana, was found to be highly active for sensitizing renal carcinoma cells and a number of other human cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. Withanolide E, the most potent and least toxic of five TRAIL-sensitizing withanolides identified, enhanced death receptor-mediated apoptotic signaling by a rapid decline in the levels of cFLIP proteins. Other mechanisms by which TRAIL sensitizers have been reported to work: generation of reactive oxygen species (ROS), changes in pro-and antiapoptotic protein expression, death receptor upregulation, activation of intrinsic (mitochondrial) apoptotic pathways, ER stress, and proteasomal inhibition proved to be irrelevant to withanolide E activity. Loss of cFLIP proteins was not due to changes in expression, but rather destabilization and/or aggregation, suggesting impairment of chaperone proteins leading to degradation. Indeed, withanolide E treatment altered the stability of a number of HSP90 client proteins, but with greater apparent specificity than the well-known HSP90 inhibitor geldanamycin. As cFLIP has been reported to be an HSP90 client, this provides a potentially novel mechanism for sensitizing cells to TRAIL. Sensitization of human renal carcinoma cells to TRAIL-induced apoptosis by withanolide E and its lack of toxicity were confirmed in animal studies. Owing to its novel activity, withanolide E is a promising reagent for the analysis of mechanisms of TRAIL resistance, for understanding HSP90 function, and for further therapeutic development. In marked contrast to bortezomib, among the best currently available TRAIL sensitizers, withanolide E's more specific mechanism of action suggests minimal toxic side effects.

Structure-activity relationship (SAR) of withanolides to inhibit Hsp90 for its activity in pancreatic cancer cells

Withaferin A (WA), a naturally occurring steroidal lactone, directly binds to Hsp90 and leads to the degradation of Hsp90 client protein. The purpose of this study is to investigate the structure activity relationship (SAR) of withanolides for their inhibition of Hsp90 and anti-proliferative activities in pancreatic cancer cells. In pancreatic cancer Panc-1 cells, withaferin A (WA) and its four analogues withanolide E (WE), 4-hydroxywithanolide E (HWE), 3-aziridinylwithaferin A (AzWA) inhibited cell proliferation with IC50 ranged from 1.0 to 2.8 μM. WA, WE, HWE, and AzWA also induced caspase-3 activity by 21-, 6-, 11- and 15-fold, respectively, in Panc-1 cells, while withaperuvin (WP) did not show any activity. Our data showed that WA, WE, HWE, and AzWA, but not WP, all directly bound to Hsp90 and induced Hsp90 aggregation,hence inhibited Hsp90 chaperone activity to induce degradation of Hsp90 client proteins Akt and Cdk4 through proteasome-dependent pathway in pancreatic cancer cells. However, only WA, HWE and AzWA disrupted Hsp90-Cdc37 complexes but not WE and WP. SAR study suggested that the C-5(6)-epoxy functional group contributes considerably for withanolide to bind to Hsp90, inhibit Hsp90 chaperone activity, and result in Hsp90 client protein depletion. Meanwhile, the hydroxyl group at C-4 of ring A may enhance withanolide to inhibit Hsp90 activity and disrupt Hsp90-Cdc37 interaction. These SAR data provide possible mechanisms of anti-proliferative action of withanolides.

Water extract of Ashwagandha leaves has anticancer activity: identification of an active component and its mechanism of action

Background

Cancer is a leading cause of death accounting for 15-20% of global mortality. Although advancements in diagnostic and therapeutic technologies have improved cancer survival statistics, 75% of the world population live in underdeveloped regions and have poor access to the advanced medical remedies. Natural therapies hence become an alternative choice of treatment. Ashwagandha, a tropical herb used in Indian Ayurvedic medicine, has a long history of its health promoting and therapeutic effects. In the present study, we have investigated an anticancer activity in the water extract of Ashwagandha leaves (ASH-WEX).

Methodology/Principal Findings

Anticancer activity in the water extract of Ashwagandha leaves (ASH-WEX) was detected by invitro and invivo assays. Bioactivity-based size fractionation and NMR analysis were performed to identify the active anticancer component(s). Mechanism of anticancer activity in the extract and its purified component was investigated by biochemical assays. We report that the ASH-WEX is cytotoxic to cancer cells selectively, and causes tumor suppression invivo. Its active anticancer component was identified as triethylene glycol (TEG). Molecular analysis revealed activation of tumor suppressor proteins p53 and pRB by ASH-WEX and TEG in cancer cells. In contrast to the hypophosphorylation of pRB, decrease in cyclin B1 and increase in cyclin D1 in ASH-WEX and TEG-treated cancer cells (undergoing growth arrest), normal cells showed increase in pRB phosphorylation and cyclin B1, and decrease in cyclin D1 (signifying their cell cycle progression). We also found that the MMP-3 and MMP-9 that regulate metastasis were down regulated in ASH-WEX and TEG-treated cancer cells; normal cells remained unaffected.

Conclusion

We provide the first molecular evidence that the ASH-WEX and TEG have selective cancer cell growth arrest activity and hence may offer natural and economic resources for anticancer medicine.

Current status on development of steroids as anticancer agents

Steroids are important biodynamic agents. Their affinities for various nuclear receptors have been an interesting feature to utilize them for drug development particularly for receptor mediated diseases. Steroid biochemistry and its crucial role in human physiology, has attained importance among the researchers. Recent years have seen an extensive focus on modification of steroids. The rational modifications of perhydrocyclopentanophenanthrene nucleus of steroids have yielded several important anticancer lead molecules. Exemestane, SR16157, fulvestrant and 2-methoxyestradiol are some of the successful leads emerged on steroidal pharmacophores. The present review is an update on some of the steroidal leads obtained during past 25 years. Various steroid based enzyme inhibitors, antiestrogens, cytotoxic conjugates and steroidal cytotoxic molecules of natural as well as synthetic origin have been highlighted. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

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.

Molecular insight in the multifunctional activities of Withaferin A

Herbal medicine which involves the use of plants for their medicinal value, dates as far back as the origin of mankind and demonstrates an array of applications including cardiovascular protection and anti-cancer activities, via antioxidant, anti-inflammatory and metabolic activities. Even today the popularity of medicinal herbs is still growing like in traditional medicines such as the Indian medicine, Ayurveda. One of the Ayurvedic medicinal plants is Withania somnifera Dunal, of which the important constituents are the withanolides. Among them, Withaferin A is one of the most bioactive compounds, exerting anti-inflammatory, pro-apoptotic but also anti-invasive and anti-angiogenic effects. In the context of modern pharmacology, a better insight in the underlying mechanism of the broad range of bioactivities exerted by Withaferin A is compulsory. Therefore, a lot of effort was made to explore the intracellular effects of Withaferin A and to characterize its target proteins. This review provides a decisive insight on the molecular basis of the health-promoting potential of Withaferin A.