Isolation, purification and structure elucidation of eight saponin compounds from Calotropis gigantea

Identifying the active ingredient from plant extracts and establishing its safety and efficacy remains a challenge, so there is need to develop optimised Isolation and purification method to concentrate the natural product from plant resources. In the key content areas of Pharmaceutical, natural product Industry and food application. Asclepiadaceae perennial herb Calotropis gigantea has a long history of usage in folk medicine. The purpose of this study to isolate, purified and structure elucidation of the saponin compounds. As per the Literature study reported that, the saponin compounds remain a huge source for medicinal, are rich sources of chemical compounds having tremendous diversity with respect to structure, function and mechanism of action. In this study we selected Calotropis gigantea for the separation of the saponin. In the present study we successfully isolated, purified, elucidated the structure and identified the saponin compounds using HPLC and HR LC-MS techniques.

Calotropis gigantea stem bark extract activates HepG2 cell apoptosis through ROS and its effect on cytochrome P450

The 95% ethanolic extract of the dry powder of Calotropis gigantea (C. gigantea) stem bark was separated by fractionation with different solutions to yield 4 fractions: dichloromethane (CGDCM), ethyl acetate (CGEtOAc), and water (CGW). This research focused on CGDCM-induced apoptosis in HepG2 cells with IC50 and above-IC50 values, which provide useful information for future anticancer applications. CGDCM had lower cytotoxicity on normal lung fibroblast IMR-90 cells than on HepG2 cells. Apoptotic induction of CGDCM was mediated by decreased fatty acid and ATP synthesis while increasing reactive oxygen species production. The effects of the four extracts on the activity of the four major CYP450 isoforms (CYP1A2, CYP2C9, CYP2E1 and CYP3A4) were determined using the CYP-specific model activity of each isoform. All four fractions of the extract were shown to be poor inhibitors of CYP1A2 and CYP2E1 (IC50 > 1000 μg/mL) and moderate inhibitors of CYP3A4 (IC50 = 56.54-296.9 μg/mL). CGDCM and CGW exerted moderate inhibition activities on CYP2C9 (IC50 = 59.56 and 46.38 μg/mL, respectively), but CGEtOH and CGEtOAc exhibited strong inhibition activities (IC50 = 12.11 and 20.43 μg/mL, respectively). It is proposed that C. gigantea extracts at high doses have potential for further studies to develop alternative anticancer applications. Inhibiting CYP2C9 activity may also lead to drug-herb interactions.

Green Chemistry Based Synthesis of Zinc Oxide Nanoparticles Using Plant Derivatives of Calotropis gigantea (Giant Milkweed) and Its Biological Applications against Various Bacterial and Fungal Pathogens

Nanotechnology is a burning field of scientific interest for researchers in current era. Diverse plant materials are considered as potential tool in green chemistry based technologies for the synthesis of metal nanoparticles (NPs) to cope with the hazardous effects of synthetic chemicals, leading to severe abiotic climate change issues in today's agriculture. This study aimed to determine the synthesis and characterization of metal-based nanoparticles using extracts of the selected plant Calotropis gigantea and to evaluate the enzyme-inhibition activities and antibacterial and antifungal activity of extracts of metal-based zinc nanoparticles using C. gigantea extracts. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). C. gigantea was examined for antimicrobial activity against clinical isolates of bacteria and fungi. The water, ethanolic, and acetone extracts of C. gigantea were studied for their antagonistic action against bacterial strains (E. coli, S. aureus, P. multocida, and B. subtilis) and selected fungal strains (A. paracistic, F. solani, A. niger, S. ferrugenium, and R. nigricans). In vitro antimicrobial activity was determined by the disc diffusion method, where C. gigantea wastested for AChE and BChE inhibitory activity using Ellman's methodology. The kinetic analysis was performed by the proverbial Berthelot reaction for urease inhibition. The results showed that out of all the extracts tested, ethanolic and water extracts possessed zinc nanoparticles. These extracts showed the maximum zone of inhibition against F. solani and P. multocida and the lowest against S. ferrugenium and B. subtilis. A potential source of AChE inhibitors is certainly provided by the abundance of plants in nature. Numerous phyto-constituents, such as AChE and BChE inhibitors, have been reported in this communication. Water extract was active and has the potential for in vitro AChE and BChE inhibitory activity. The urease inhibition with flower extracts of C. gigantea revealed zinc nanoparticles in water extracts that competitively inhibited urease enzymes. In the case of cholinesterase enzymes, it was inferred that the water extract and zinc nanoparticles have more potential for inhibition of BChE than AChE and urease inhibition. Furthermore, zinc nanoparticles with water extract are active inthe inhibition of the bacterial strains E. coli, S. aureus, and P. multocida and the fungal strains A. paracistic, F. solani, and A. niger.

Polyphagous insect Olepa sps. feeding on cardenolide rich Calotropis gigantea (L.) leaves and detoxification mechanism involving GST

Cardenolides, a group of cardiac glycosides are potent inhibitors of Na⁺/K⁺ ATPase pump in mammals, animals including insects. Some insects can circumvent the toxicity of cardenolides by mechanisms like target site resistance and metabolic resistance resulting in enhanced tolerance or adaptation. In this paper, we report an intriguing observation of a polyphagous feeder feeding gregariously on the leaves of Calotropis gigantea (L.) without any apparent adverse effect. No choice feeding assay showed higher larval biomass and reduced number of days to develop on C. gigantea leaves compared to Ricinus and banana. We found the activity of GST higher in C. gigantea fed larva and HR LC-MS analysis of Olepa sps. revealed the presence of glutathione-strophanthidin conjugate in larval body tissue. In silico molecular simulation results confirmed strong interaction between delta variant GST and glutathione-strophanthidin complex. The sequestration site and cost benefit of glutathione-strophanthidin sequestration in body tissues of Olepa sps. needs further investigation.

Anti-migraine activity of freeze-dried latex obtained from Calotropis gigantea Linn

Migraine which is characterized by a pulsating headache affected an estimated population of 12% worldwide. Herbal products like latex derived from Calotropis gigantea R. Br. (Asclepiadaceae) are a representative intervention to treat migraine traditionally. However, post-harvesting stability issues of latex affect its biological potential. Freeze-drying has been successfully employed for the encapsulation of herbal bioactive compounds resulting in stable dried preparations. Latex derived from Calotropis gigantea (C. gigantea) was microencapsulated using chitosan by freeze-drying (FDCG) method and compared with sun ray-dried latex (ADCG). Current investigation was aimed to improve the shelf life of latex by freeze-drying microencapsulation technique and evaluation of its anti-migraine potential. Dried latex powders (ADCG and FDCG) were evaluated in terms of phenolic content, coloring strength, first-order kinetic, color parameters (L*, a*, b*, C*, and E*), moisture, water activity, solubility, and hygroscopicity. Additionally, apomorphine-induced climbing behavior, L-5-HTP-induced syndrome, and MK-801-induced hyperactivity were used to evaluate the anti-migraine potential of powdered latex. FDCG showed good physicochemical properties due to its higher concentration of phenolic and flavonoid contents. Moreover, FDCG significantly reduced the apomorphine-induced climbing behavior, L-5-HTP-induced syndrome, and MK-801-induced hyperactivity in a dose-dependent manner through an interaction of dopaminergic and serotonergic receptors. In conclusion, the method developed for shelf life improvement of latex offered maximum protection over a period of 10 weeks with retaining its natural biological potential; thus, it can be effectively utilized in the treatment or management of migraine. Anti-migraine effect of Calotropis gigantea freeze-dried latex by inhibition of dopamine and serotonin receptors (D1 and D2: dopamine receptors; 5-HT: serotonin receptors); yellow color represents serotonergic, and blue color indicates dopaminergic neurons.

Virus-Induced Gene Silencing for Functional Genomics of Specialized Metabolism in Medicinal Plants

Virus-induced gene silencing (VIGS) is a functional genomics tool to transiently downregulate the expression of target gene(s) by exploiting the plant's innate defense mechanism against invading RNA viruses. VIGS is a rapid and efficient approach to analyze the gene function, particularly, in the plants that are not amenable to stable genetic transformation. This strategy has been successfully used to decipher the function of several genes and transcription factors involved in the biosynthesis of specialized metabolites and regulation of specialized metabolism, respectively, in different medicinal and aromatic plants. Here, we describe a detailed Tobacco rattle virus (TRV)-mediated VIGS protocol for silencing of the gene encoding Phytoene desaturase (PDS) in important medicinal plants Catharanthus roseus, Calotropis gigantean, Rauwolfia serpentina, and Ocimum basilicum. Our methods allow the study of gene function within 3-4 weeks after agro-inoculation, and can be an easy and efficient approach for future studies on understanding of the biosynthesis of specialized metabolites in these important medicinal plants.

Molecular docking investigation of calotropone as a potential natural therapeutic agent against pancreatic cancer

A natural bioactive compound named calotropone has been reported as a drug candidate for several cancers, including pancreatic cancers. Herein, we used molecular docking approach to test the possible mechanisms of action of calotropone in inhibiting the growth of pancreatic cell cancer with gemcitabine as the positive control. By employing AutoDock Vina, we studied the molecular interaction between calotropone and pancreatic cancer-associated proteins, namely Glucosaminyl (N-Acetyl) Transferase 3, Glutamic-Oxaloacetic Transaminase 1, Tyrosine-protein kinase Met (c-Met), peroxisome proliferator-activated receptor γ, Budding Uninhibited by Benzimidazole 1, A Disintegrin and Metalloproteinase 10, Sex-determining region Y and Nuclear Factor kappa Beta (Nf-Kβ). Higher affinity energies of calotropone toward the aforementioned proteins (ranging from ‒7.3 to ‒9.3 kcal/mol) indicate that calotropone may work in the same manner as anticancer drug gemcitabine. Highest docking score was found at the interaction of calotropone and Nf-Kβ (‒9.3 kcal/mol).

Cytotoxic cardenolides from Calotropis gigantea

Sixteen cardiac glycosides, including five previously undescribed compounds, were extracted and purified from whole plants of Calotropis gigantea (L.). Spectroscopic data and electronic circular dichroism (ECD) analyses were used to determine their structures. Calogiganin C is the first naturally occurring example of a cardenolide containing a 7-membered lactone in ring A. The cytotoxic activities of these compounds against A172, U251, AGS, PANC-1, HepG2, HCT116 and NCI-H226 cell lines were evaluated. Four of them exhibited the most potent growth inhibitory activity against a panel of human cancer cell lines, including A172, U251, AGS, PANC-1 and HCT116. Notably, uscharidin and calotropin showed pronounced cytotoxicities at low nanomolar concentrations against A172 and U251 cells, and possible cell death mechanism studies manifested that these two compounds induced G2/M cell cycle arrest, which demonstrated promising anticancer potential.

Evaluation of the Phytochemical, Antioxidant, Enzyme Inhibition, and Wound Healing Potential of Calotropis gigantea (L.) Dryand: A Source of a Bioactive Medicinal Product

Traditionally, plants of the genus Calotropis have been used to cure various common diseases. The present research work explores the chemical and biological characterization of one of the most common species of this genus, i.e., Calotropis gigantea (L.) Dryand (syn. Calotropis gigantea (L.) Dryand.), having multiple folklore applications. The ethanolic extract of leaves of Calotropis gigantea (L.) Dryand was analyzed for the phytochemical composition by determining the total bioactive (total phenolic and total flavonoid) contents and UHPLC-MS secondary metabolites analysis. For phytopharmacological evaluation, in vitro antioxidant (including DPPH, ABTS, FRAP, CUPRAC, phosphomolybdenum, and metal chelation antioxidant assays) activities, enzyme inhibition potential (against AChE, BChE, α-amylase, and tyrosinase enzymes), and in vivo wound healing potential were determined. The tested extract has been shown to contain considerable flavonoid (46.75 mg RE/g extract) and phenolic (33.71 mg GAE/g extract) contents. The plant extract presented considerable antioxidant potential, being the most active for CUPRAC assays. Secondary metabolite UHPLC-MS characterization, in both the positive and negative ionization modes, indicated the tentative presence of 17 different phytocompounds, mostly derivatives of sesquiterpene, alkaloids, and flavonoids. Similarly, the tested extract exhibited considerable inhibitory effects on tyrosinase (81.72 mg KAE/g extract), whereas it showed weak inhibition ability against other tested enzymes. Moreover, in the case of in vivo wound healing assays, significant improvement in wound healing was observed in both the tested models at the doses of 0.5 percent w/w (p < 0.001) and 2.0 percent w/w (p < 0.01) on the 16^th day. The outcomes of the present research work suggested that C. gigantea (L.) Dryand plant extract could be appraised as a potential origin of bioactive molecules having multifunctional medicinal uses.

Molecular docking of two cytotoxic compounds from Calotropis gigantea leaves against therapeutic molecular target of pancreatic cancer

The utilization of natural compounds as therapeutic agents to treat pancreatic cancer has recently focused on natural drug research. Calotropis gigantea has long been believed to be a medicinal plant that helps in treating various diseases. The bioactive compounds 9-metoxipinoresinol and isoliquiritigenin isolated from C. gigantea leaves are proven to act as therapeutic agents by inhibiting the cancer cell growth of Panc-1 cells. This study aimed to screen the potential molecular inhibition mechanisms of 9-metoxipinoresinol and isoliquiritigenin against pancreatic cancer development in-silico. We analyzed the activity of the aforementioned two compounds as inhibitors of several proteins that play a role in the growth of pancreatic cancer cells, such as GCNT3, GOT1, c-Met, PPARγ, BUB1, and NF-κβ, through molecular docking investigation. Our data suggested that 9-metoxipinoresinol and isoliquiritigenin were able to have well interaction with the target proteins, in which the predicted affinity energy ranged between -6.8 and 8.7 kcal/mol. The docking scores of 9-metoxipinoresinol and isoliquiritigenin were higher than the standard drug used (gemcitabine). Based on the binding affinity energy, GCNT3 and BUB1 are potentially to be used as target molecules for cancer therapy using 9-metoxipinoresinol and isoliquiritigenin, respectively.

Appraisals of the Bangladeshi Medicinal Plant Calotropis gigantea Used by Folk Medicine Practitioners in the Management of COVID-19: A Biochemical and Computational Approach

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first recognized in Wuhan in late 2019 and, since then, had spread globally, eventually culminating in the ongoing pandemic. As there is a lack of targeted therapeutics, there is certain opportunity for the scientific community to develop new drugs or vaccines against COVID-19 and so many synthetic bioactive compounds are undergoing clinical trials. In most of the countries, due to the broad therapeutic spectrum and minimal side effects, medicinal plants have been used widely throughout history as traditional healing remedy. Because of the unavailability of synthetic bioactive antiviral drugs, hence all possible efforts have been focused on the search for new drugs and alternative medicines from different herbal formulations. In recent times, it has been assured that the Mpro, also called 3CLpro, is the SARS-CoV-2 main protease enzyme responsible for viral reproduction and thereby impeding the host's immune response. As such, Mpro represents a highly specified target for drugs capable of inhibitory action against coronavirus disease 2019 (COVID-19). As there continue to be no clear options for the treatment of COVID-19, the identification of potential candidates has become a necessity. The present investigation focuses on the in silico pharmacological activity of Calotropis gigantea, a large shrub, as a potential option for COVID-19 Mpro inhibition and includes an ADME/T profile analysis of that ligand. For this study, with the help of gas chromatography-mass spectrometry analysis of C. gigantea methanolic leaf extract, a total of 30 bioactive compounds were selected. Our analyses unveiled the top four options that might turn out to be prospective anti-SARS-CoV-2 lead molecules; these warrant further exploration as well as possible application in processes of drug development to combat COVID-19.

Non-classical cardenolides from Calotropis gigantea exhibit anticancer effect as HIF-1 inhibitors

Six new non-classical cardenolides (1-6), and seventeen known ones (7-23) were isolated from Calotropis gigantea. All cardenolides showed inhibitory effect on hypoxia inducible factor-1 (HIF-1) transcriptional activity with IC₅₀ of 8.85 nM-16.69 µM except 5 and 7. The novel 19-dihydrocalotoxin (1) exhibited a comparable HIF-1 inhibitory activity (IC₅₀ of 139.57 nM) to digoxin (IC₅₀ of 145.77 nM), a well-studied HIF-1 inhibitor, and 11, 12, 14, 16 and 19 presented 1.4-15.4 folds stronger HIF-1 inhibition than digoxin. 1 and 11 showed a dose-dependent inhibition on HIF-1α protein, which led to their HIF-1 suppressing effects. Compared with LO2 and H9c2 normal cell lines, both 1 and 11 showed selective cytotoxicity against various cancer cell lines including HCT116, HeLa, HepG2, A549, MCF-7, A2780 and MDA-MB-231. Moreover, a comprehensive structure-activity relationship was concluded for these non-classical cardenolides as HIF-1 inhibitors, which may shed some light on the rational design and development of cardenolide-based anticancer drugs.

Characterization and valuable use of Calotropis gigantea seedpods as a biosorbent of methylene blue

In this work, powdered Calotropis gigantea seedpods were characterized and used as biosorbents of methylene blue dye from aqueous solution. FT-IR spectroscopy demonstrated functional groups characteristics of cellulose. Steric exclusion chromatography donated an average molecular weight of 230 kg/mol of the biopolymer. The polymolecularity index value (1.95) proved the good homogeneity of the polysaccharide. Scanning electron microscopy features displayed a homogenous morphology and porous structure. X-ray diffraction patterns showed peaks characteristics of cellulose and non-cellulose compositions. Thermogravimetric analysis/differential thermal analysis displayed exothermal decompositions at 316.9 °C and 456 °C. The maximum biosorption capacity of methylene blue was 88.36 mg/g at pH = 6, time = 60 min, and T = 21 °C. The level was comparable to some other studied agricultural wastes. The adsorption mechanism followed pseudo-second-order and Freundlich models. As it is abundant, available, low-cost, and easily recovered from solution, C. gigantea seedpods could be used as an effective biomaterial for the removal of organic pollutants from contaminated waters. Novelty statement: An abundant, available, and low-cost Calotropis gigantea seedpod was used, for the first time, as an effective biomaterial for the biosorption of organic pollutants. The biosorption level was found to be comparable to some other agricultural wastes studied previously in the literature.

A new cytotoxic cardenolide from the roots of Calotropis gigantea

Bioactivity-guided isolation of the CHCl₃-soluble fraction of the roots of Calotropis gigantea was carried out to obtain a new cardenolide glycoside, caloside G. Its absolute structure was elucidated based on NMR and ECD spectroscopic data interpretation. Caloside G showed noteworthy cytotoxicity against the PANC-1 human pancreatic and HeLa human cervical carcinoma cell lines, with the submicromolar IC₅₀ values of 0.038 and 0.09 µM, respectively.

Effective Inhibition of Candidiasis Using an Eco-Friendly Leaf Extract of Calotropis-gigantean-Mediated Silver Nanoparticles

The approaches used for the green biosynthesis of nanoparticles with clinical applications have been widely used in nanotechnology due to their potential to provide safe, eco-friendly, cost effective, high-stability, and high-loading-capacity nanoparticles. This study aimed to evaluate the anti-candidal activity of silver nanoparticles (AgNPs) biosynthesized using the aqueous leaf extract of Calotropis gigantea (CG) alone or in a combination with the plant extract of CG (AgNPs/CG). AgNPs were characterized using UV-Vis spectrophotometry, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results of the standard disk diffusion method revealed that AgNPs alone displayed anti-candidal activity (11.33-mm inhibition zone), while AgNPs/CG displayed a strong synergistic anti-candidal activity (17.76-mm inhibition zone). Similarly, AgNPs/CG completely inhibited the growth of C. albicans after 4 h of incubation, as measured using the time-kill assay. In addition, AgNPs/CG inhibited the dimorphic transition of C. albicans and suppressed both the adhesion and the biofilm formation of C. albicans by 41% and 38%, respectively. The treatment of Candida. albicans with AgNPs/CG showed a significant inhibition of the production of several antioxidant enzymes. Interestingly, AgNPs/CG did not show any cytotoxicity in animal cells, including the MCF-7 cell line and primary mouse bone marrow-derived mesenchymal stem cells (mBMSCs), at the concentration used to completely inhibit the dimorphic transition of C. albicans. In conclusion, we identified AgNPs/CG as a promising natural-product-based nanoparticle that can potentially be used as an anti-candidal drug.

Calotropis gigantea extract induces apoptosis through extrinsic/intrinsic pathways and reactive oxygen species generation in A549 and NCI-H1299 non-small cell lung cancer cells

Background

Calotropis gigantea (CG) is a tall and waxy flower that is used as a traditional remedy for fever, indigestion, rheumatism, leprosy, and leukoderma. However, the precise mechanisms of its anticancer effects have not yet been examined in human non-small cell lung cancer (NSCLC) cells. In this study, we investigated whether CG extract exerted an apoptotic effect in A549 and NCI-H1299 NSCLC cells.

Methods

The ethanol extract of CG was prepared, and its apoptotic effects on A549 and NCI-H1299 NSCLC cells were assessed by using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxy methoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay, annexin V-fluorescein isothiocyanate/propidium iodide (PI) staining, cell cycle analysis, real-time polymerase chain reaction (RT-PCR), western blotting, JC-1 staining, and ROS detection assay.

Results

The CG extract induced apoptosis through the stimulation of intrinsic and extrinsic signaling pathways in A549 and NCI-H1299 lung cancer cells. Cell cycle arrest was induced by the CG extract in both cell lines. Reactive oxygen species (ROS), which can induce cell death, were also generated in the CG-treated A549 and NCI-H1299 cells.

Conclusions

These data confirmed that CG caused apoptosis through the activation of extrinsic and intrinsic pathways, cell cycle arrest, and ROS generation in A549 and NCI-H1299 lung cancer cells. Thus, CG can be suggested as a potential agent for lung cancer therapy.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2561-1) contains supplementary material, which is available to authorized users.

Population Genetics of Calotropis gigantea, a Medicinal and Fiber Resource Plant, as Inferred from Microsatellite Marker Variation in two Native Countries

Calotropis gigantea is well known for its aesthetic, medicinal, pharmacological, fodder, fuel, and fiber production potential. Unfortunately, this plant species is still undomesticated, and the genetic information available for crop improvement is limited. For this study, we sampled 21 natural populations of C. gigantea from two key areas of its natural distribution range (Bangladesh and China) and genotyped 379 individuals using nine nuclear microsatellite markers. Population genetic diversity was higher in Bangladesh than that observed in Chinese populations. Overall, a moderate level of genetic diversity was found (N_a = 3.73, H_E = 0.466), with most of the genetic variation detected within populations (65.49%) and substantial genetic differentiation (F_ST = 0.345) between the study regions. We observed a significant correlation between genetic and geographic distances (r  =  0.287, P  =  0.001). The Bayesian clustering, UPGMA tree, and PCoA analyses yielded three distinct genetic pools, but the number of migrants per generation was high (N_M = 0.52-2.78) among them. Our analyses also revealed that some populations may have experienced recent demographic bottlenecks. Our study provides a baseline for exploitation of the genetic resources of C. gigantea in domestication and breeding programs as well as some insights into the germplasm conservation of this valuable plant.

Calotroposid A: a Glycosides Terpenoids from Calotropis gigantea Induces Apoptosis of Colon Cancer WiDr Cells through Cell Cycle Arrest G2/M and Caspase 8 Expression

Objective:

This study aims to isolate the active anticancer compound from ethyl acetate fraction extracted from the roots of Calotropis gigantea and to determine the operating mechanism of the isolates towards WiDr colon cancer cells.

Methods:

the isolation was conducted by using bioassay guided isolation approach method. The cytotoxic potential was determined by using MTT method. The chemical structure was identified by using UPLCMS/MS and NMR-1H spectroscopy. The cell cycle arrest and apoptosis induction were determined by flow cytometry method. The expression of caspase-8 was determined by immunocytochemistry method.

Results:

The results showed that the active compounds are obtained calotroposid A compound which is glycosides terpenoids. Calotroposide A is capable of inhibiting the growth of WiDr colon cancer cells at IC₅₀ 17.23µg/ml. Cell apoptosis induction took place and was indicated by cell apoptosis increase, S and G2/M accumulation and by caspase-8 expression.

Conclusion:

Calotroposide A induces anticancer activity against WiDr colon cancer cells by means of apoptosis induction mechanism through extrinsic pathway with increased expression of caspase-8.

Coroglaucigenin enhances the radiosensitivity of human lung cancer cells through Nrf2/ROS pathway

Seven cardenolides isolated from the ethanol extract of the stems of Calotropis gigantea were evaluated in vitro against human cancer cells and the structure-activity relationships were discussed. The results demonstrated that a compound, named CGN (coroglaucigenin), had better anti-proliferative activity with the IC50 value less than 6 μM among these compounds. Further, we found that CGN displayed much lower cytotoxicity to normal lung epithelial cells (BEAS-2B) than cancer cells (A549). Especially, our results demonstrated that treatment with CGN (1 μM) combined with X-ray irradiation induced higher radiosensitivity in human lung cancer cells (A549, NCI-H460, NCI-H446) but not in BEAS-2B. The expression levels of nuclear transcription factor Nrf2 and Nrf2-driven antioxidant molecule NQO-1 reduced in A549 cells after combined treatment compared to the radiation only. However, CGN had no toxicity and the levels of antioxidant molecules expression were higher in BEAS-2B cells when given the similar treatment as A549 cells. These results suggest that CGN is a very promising potential sensitizer for cancer radiotherapy, which not only inhibits the proliferation of cancer cells but also enhances the radiosensitivity of cancer cells through suppressing the expression of antioxidant molecules while there is no influence for normal cells.

Genome Assembly and Annotation of the Medicinal Plant Calotropis gigantea, a Producer of Anticancer and Antimalarial Cardenolides

Calotropis gigantea produces specialized secondary metabolites known as cardenolides, which have anticancer and antimalarial properties. Although transcriptomic studies have been conducted in other cardenolide-producing species, no nuclear genome assembly for an Asterid cardenolide-producing species has been reported to date. A high-quality de novo assembly was generated for C. gigantea, representing 157,284,427 bp with an N50 scaffold size of 805,959 bp, for which quality assessments indicated a near complete representation of the genic space. Transcriptome data in the form of RNA-sequencing libraries from a developmental tissue series was generated to aid the annotation and construction of a gene expression atlas. Using an ab initio and evidence-driven gene annotation pipeline, 18,197 high-confidence genes were annotated. Homologous and syntenic relationships between C. gigantea and other species within the Apocynaceae family confirmed previously identified evolutionary relationships, and suggest the emergence or loss of the specialized cardenolide metabolites after the divergence of the Apocynaceae subfamilies. The C. gigantea genome assembly, annotation, and RNA-sequencing data provide a novel resource to study the cardenolide biosynthesis pathway, especially for understanding the evolutionary origin of cardenolides and the engineering of cardenolide production in heterologous organisms for existing and novel pharmaceutical applications.

Calotropis gigantea extract as a potential anticariogenic agents against Streptococcus mutans: An in vivo comparative evaluation

Objective:

The current study was intended to evaluate and compare the in vivo efficacy of Calotropis gigantea mouth rinse as anticariogenic agents with 0.2% chlorhexidine and Listerine mouth rinse.

Materials and Methods:

An experimental crossover study was conducted on sixty school children aged 14–15 years. Participants were divided into three Groups A, B, and C. In all children, baseline unstimulated saliva samples were collected and assessed for Streptococcus mutans counts. The study was conducted in three phases; each phase lasted for 8 days separated by a washout period of 15 days in between them. Groups A, B, and C were treated with 0.2% chlorhexidine, Listerine and C. gigantea extract mouth rinses, respectively, in the Phase I and assessed for salivary S. mutans counts. Subsequently, mouth rinses were crossed over as dictated by the Latin square design in Phase II and III.

Results and Conclusion:

All the three mouth rinses have individually shown a statistically significant reduction in the salivary S. mutans counts.

Green Synthesized Zinc Oxide (ZnO) Nanoparticles Induce Oxidative Stress and DNA Damage in Lathyrus sativus L. Root Bioassay System

Zinc oxide nanoparticles (ZnONP-GS) were synthesised from the precursor zinc acetate (Zn(CH₃COO)₂) through the green route using the milky latex from milk weed (Calotropis gigantea L. R. Br) by alkaline precipitation. Formation of the ZnONP-GS was monitored by UV-visible spectroscopy followed by characterization and confirmation by energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Both the ZnONP-GS and the commercially available ZnONP-S (Sigma-Aldrich) and cationic Zn²⁺ from Zn(CH₃COO)₂ were tested in a dose range of 0–100 mg·L⁻¹ for their potency (i) to induce oxidative stress as measured by the generation reactive oxygen species (ROS: O₂^•−, H₂O₂ and ^•OH), cell death, and lipid peroxidation; (ii) to modulate the activities of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX); and (iii) to cause DNA damage as determined by Comet assay in Lathyrus sativus L. root bioassay system. Antioxidants such as Tiron and dimethylthiourea significantly attenuated the ZnONP-induced oxidative and DNA damage, suggesting the involvement of ROS therein. Our study demonstrated that both ZnONP-GS and ZnONP-S induced oxidative stress and DNA damage to a similar extent but were significantly less potent than Zn²⁺ alone.

Cardenolides from Calotropis gigantea as potent inhibitors of hypoxia-inducible factor-1 transcriptional activity

ETHNOPHARMACOLOGICAL RELEVANCE

Calotropis gigantea (L.) Dryand (Apocynaceae) is a medicinal plant native to southern China, India and Southeast Asia. It has been traditionally used for the treatment of several diseases including cancers in these countries.

AIM OF THE STUDY

This study aimed to isolate bioactive cardenolides from C. gigantea, to screen their hypoxia-inducible factor (HIF-) 1 inhibitory activity, and to analyze the structure-activity relationship (SAR).

MATERIALS AND METHODS

Isolation and purification of cardenolides from the latex and the fruits of C. gigantea were performed by using a series of separation techniques. Their structures were fully characterized by elucidating their NMR and HRMS data. The HIF-1 inhibitory activities of cardenolides were evaluated by using a T47D cell-based dual-luciferase reporter assay. The potent cardenolides were selected to further evaluate their dose-response manner. Cytotoxic effects of selected cardenolides were also examined against breast cancer cell line (MCF-7) and normal mammary epithelial cell line (MCF-10A) by MTT assay.

RESULTS

Among twenty isolated cardenolides, compounds 1, 3, 4, 6-8, 14 and 17 exhibited stronger HIF-1 inhibitory activities than that of digoxin, a well-known HIF-1 inhibitor (P<0.001). These eight cardenolides inhibited HIF-1 transcriptional activity in a dose-dependent manner with IC₅₀ values in nanomolar potency (21.8-64.9nM). An analysis of SAR revealed the great contributions of a β-configuration of the substituents at positions of C-2' and C-3', an aldehydic moiety on C-19, and the dioxane moiety between the aglycone and sugar parts of cardenolides to the HIF-1 inhibitory activity. In contrast, a hydroxyl group at any positions of C-15, C-16 and C-4' of cardenolides showed negative effects on suppressing HIF-1 transcriptional activity. In addition, these eight cardenolides also exhibited potent cytotoxic effects against human breast cancer cell MCF-7 (IC₅₀ values ranged from 30.5 to 68.8nM), but less toxic effects to human normal mammary epithelial cell MCF-10A (IC₅₀ values >20µM).

CONCLUSIONS

This is the first report of a comprehensive study of SAR on cardenolides from C. gigantea as HIF-1 inhibitors. Eight cardenolides (1, 3, 4, 6-8, 14 and 17) showed both potent HIF-1 inhibitory activity and strong cytotoxic effect against MCF-7 cancer cells in nanomolar level. The findings of these cardenolides provided important insights into the development of these potent HIF-1 inhibitors as anticancer drug.

Cardenolides from the bark of Calotropis gigantea

Three new cardenolides (1-3) were isolated from the 90% ethanolic extract of the bark of a wild-type Calotropis gigantea. Their structures were determined by using NMR spectra and LC-MS analysis. Their inhibitory activities were evaluated against non-small cell lung carcinoma (A549) and human cervix epithelial adenocarcinoma (HeLa) cell lines. Compounds 1 and 3 exhibited strong inhibitory effect on two cancer cell lines.

Calotropin: a cardenolide from calotropis gigantea that inhibits Wnt signaling by increasing casein kinase 1α in colon cancer cells

Wnt signaling plays key roles in embryonic development and various human diseases. Activity-guided testing to isolate Wnt signaling inhibitors from the methanol extract of Calotropis gigantea (Asclepiadaceae) exudutes identified six Wnt inhibitory cardenolides (1-6), of which 1, 3, 5, and 6 exhibited potent TCF/β-catenin inhibitory activities (IC50 0.7-3.6 nM). Calotropin (1) inhibited Wnt signaling by decreasing both nuclear and cytosolic β-catenin in a dose-dependent manner, and promoted degradation of β-catenin by increasing the phosphorylation of β-catenin at Ser45 through casein kinase 1α (CK1α). Moreover, 1 significantly increased CK1α protein and mRNA levels. The results suggest that 1 inhibits the Wnt signaling pathway by increasing CK1α protein levels. To the best of our knowledge, calotropin is the first small molecule to increase CK1α levels.

Cytotoxic cardenolides from the root bark of Calotropis gigantea

Six new cardenolides (1, 2 and 11-14), along with ten known ones, were isolated from the root bark of Calotropis gigantea. The structural determination was accomplished by the 1D- and 2D-NMR spectrum as well as ESIMS analysis. The isolated compounds were evaluated for their in vitro growth inhibitory activity against human A549 and Hela cell lines. The results suggested that some of these cardenolides (compounds 1, 6, and 8) displayed potent cytotoxicities.

Leaves and Flowers in Streptozotocin-Induced Diabetic Rats

OBJECTIVES

To evaluate the hypoglycemic and anti-diabetic activity of chloroform extract of Calotropis gigantea leaves and flowers in normal rats and streptozotocin induced diabetes.

METHODS

The hypoglycemic activity in normal rats was carried out by treatment using chloroform extract of Calotropis gigantea leaf and flower 10, 20 and 50 mg/kg, orally. The oral glucose tolerance test was carried out by administering glucose (2 g/kg, p.o), to non-diabetic rats treated with leaf and flowers extracts at oral doses 10, 20 and 50 mg/kg, p.o and glibenclamide 10 mg/kg. The serum glucose was then measured at 0, 1.5, 3 and 5 hr after administration of extracts/drug. Streptozotocin-induced diabetic rats were administered the same doses of leaf and flower extracts, and standard drugs glibenclamide was given to the normal rats or 0.5 ml of 5% Tween-80, for 27 days. The blood sample from all groups collected by retro-orbital puncture on 7, 14, 21 and 27th days after administration of the extracts/drug and used for the estimation of serum glucose levels using the glucose kit.

RESULTS

The Calotropis gigantea leaves and flowers extracts were effective in lowering serum glucose levels in normal rats. Improvement in oral glucose tolerance was also registered by treatment with Calotropis gigantean. The administration of leaf and flower extracts to streptozotocin-induced diabetic rats showed a significant reduction in serum glucose levels.

CONCLUSION

It is concluded that chloroform extracts of Calotropis gigantea leaves and flowers have significant anti-diabetic activity.

Free Radical Scavenging Activity of Calotropis gigantea on Streptozotocin-Induced Diabetic Rats

Swarnabhasma, an Ayurvedic preparation containing Calotropis gigantea R. Br. (Asclepiadaceae) is extensively used by Ayurvedic physicians for treatment of diabetes mellitus, bronchial asthma, rheumatoid arthritis and nervous disorders. In the present study, we report the effect of chloroform extracts of Calotropis gigantea leaf and flower on free radical scavenging activity, and lipid profile in streptozotozin-induced diabetic rats. The lipid peroxidation, superoxide dismutase, and catalase were measured in liver homogenate and serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase, alkaline phosphatase, lipid profile were measured in blood serum. Administration of single dose of streptozotozin (55 mg/kg, i.p.) caused significant increases in lipid peroxidation, serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase, alkaline phosphatase, cholesterol and triglyceride levels, while superoxide dismutase and catalase levels were significantly decreased. Further, administration of chloroform extracts of Calotropis gigantea leaf and flower to streptozotocin-induced diabetes rats at a dose of 10, 20 and 50 mg/kg orally for 27 d lead to a significant decrease in lipid peroxidation, serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase, alkaline phosphatase, cholesterol and triglyceride levels. Consequently, superoxide dismutase and catalase levels were significantly increased. Glibenclamide was used as a positive control (10 mg/kg). It was observed that the effect of chloroform extracts of Calotropis gigantea on alkaline phosphatase, cholesterol, superoxide dismutase, serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase, levels are comparable to that of those produced by the positive control.