A Novel Insect Antifeedant Nonprotein Amino Acid from Calotropis gigantea

Natural Product-Derived Phytochemicals for Influenza A Virus (H1N1) Prevention and Treatment

Influenza A (H1N1) viruses are prone to antigenic mutations and are more variable than other influenza viruses. Therefore, they have caused continuous harm to human public health since the pandemic in 2009 and in recent times. Influenza A (H1N1) can be prevented and treated in various ways, such as direct inhibition of the virus and regulation of human immunity. Among antiviral drugs, the use of natural products in treating influenza has a long history, and natural medicine has been widely considered the focus of development programs for new, safe anti-influenza drugs. In this paper, we focus on influenza A (H1N1) and summarize the natural product-derived phytochemicals for influenza A virus (H1N1) prevention and treatment, including marine natural products, flavonoids, alkaloids, terpenoids and their derivatives, phenols and their derivatives, polysaccharides, and derivatives of natural products for prevention and treatment of influenza A (H1N1) virus. We further discuss the toxicity and antiviral mechanism against influenza A (H1N1) as well as the druggability of natural products. We hope that this review will facilitate the study of the role of natural products against influenza A (H1N1) activity and provide a promising alternative for further anti-influenza A drug development.

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.

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.

Chemical Constituents and Uses of Calotropis Procera and Calotropis Gigantea – A Review (Part I – The Plants as Material and Energy Resources)

The traditional and current use of Calotropis procera and C. gigantea, two soft-wooded, xerophytic shrubs of the family Apocynaceae, are reviewed against the background of the plants' chemical constituents and their biological properties. The focus is on the usage of the plants for building materials, natural pesticides, animal feed and bioremediative purposes.

Inhibition of IKK-β by epidioxysterols from the flowers of Calotropis gigantea (Niu jiao gua)

Background

Calotropis gigantea (Asclepiadaceae) (Niu jiao gua) has been used as a poultice in Chinese medicine for treating inflammatory skin diseases, e.g., neurodermatitis. This study aims to isolate the epidioxysterols from the flowers of C. gigantea, elucidate their structures and evaluate their possible inhibitory effects on the NF-κB pathway.

Methods

The two epidioxysterols 9,11-dehydroergosterol peroxide (1) and ergosterol peroxide (2) were isolated from the powdered flowers of C. gigantea by ultrasonic-assisted extraction, followed by the purification of the crude extract by column chromatography (i.e., silica gel and MCI-gel CHP 20P open columns). The chemical structures of these compounds were identified through a comparison of their HRMS, ¹H and ¹³C NMR data with those in the literature. The in vitro IKK-β inhibitory activities of compounds 1 and 2 (1–100 µM) were evaluated using an IKK α and β Assay/Inhibitor Screening Kit, which is a single-site, semi-quantitative immunoassay. Berberine was used as a positive control. The IKK-β inhibitory activities between compounds 1 and 2 were compared by a two-tailed Student’s t test to summarize the structure activity relationship.

Results

Compounds 1 and 2 exhibited a dose-dependent inhibitory activity towards IKK-β in a similar manner to that of berberine. The IKK-β inhibitory activities of these two epidioxysterols were significantly stronger (P = 0.001 for compound 1 and P = 0.028 for compound 2) than that of berberine at the concentration of 100 µM. Furthermore, at the same concentration the suppressive effect of compound 1 towards IKK-β was greater than that of compound 2 (P = 0.041), while their activities at 10 and 50 µM were comparable. The difference in the results at 100 µM therefore suggested that the double bond between C-9 and C-11 in compound 1 could be responsible for its higher inhibitory activity towards IKK-β at this concentration.

Conclusions

9,11-dehydroergosterol peroxide (1) and ergosterol peroxide (2) were isolated from the flowers of C. gigantea and exhibited in vitro inhibitory activities towards IKK-β.

Electronic supplementary material

The online version of this article (doi:10.1186/s13020-016-0081-1) contains supplementary material, which is available to authorized users.

In vitro anti-influenza virus activities of a new lignan glycoside from the latex of Calotropis gigantea

A new lignan glycoside, (+)-pinoresinol 4-O-[6″-O-vanilloyl]-β-d-glucopyranoside (1) and two known phenolic compounds, 6′-O-vanilloyltachioside (2) and 6′-O-vanilloylisotachioside (3) were isolated from the latex of Calotropis gigantea (Asclepiadaceae). The structure of the new compound was elucidated by using spectroscopic and chemical methods. Three isolates (1–3) and one authentic compound, (+)-pinoresinol 4-O-β-d-glucopyranoside, were screened for A/PR/8/34 (H1N1) inhibitory activity by cytopathic effect (CPE) inhibition assay on MDCK cells. Compound 1 showed inhibitory activity against A/PR/8/34 (H1N1). In sharp contrast, the other three compounds (2, 3 and (+)-pinoresinol 4-O-β-d-glucopyranoside) did not show such activity. An analysis of structure-activity relationship between 1 and (+)-pinoresinol 4-O-β-d-glucopyranoside revealed that the presence of a vanilloyl group in the sugar moiety of 1 is crucial for its anti-influenza virus activity. Compound 1 was further evaluated for in vitro inhibitory activities against a panel of human and avian influenza viruses by CPE inhibition assay. It showed inhibitory effect against human influenza viruses in both subtypes A and B (IC₅₀ values around 13.4–39.8 µM with SI values of 3.7–11.4), while had no effect on avian influenza viruses. Its antiviral activity against human influenza viruses subtype A was further confirmed by plaque reduction assay. The time course assay indicated that 1 exerts its antiviral activity at the early stage of viral replication. A mechanistic study showed that 1 efficiently inhibited influenza virus-induced activation of NF-κB pathway in a dose-dependent manner, but had no effect on virus-induced activation of Raf/MEK/ERK pathway. Further studies demonstrated that nuclear translocation of transcription factor NF-κB induced by influenza virus was significantly blocked by 1, meanwhile, nuclear export of viral ribonucleoproteins was also effectively inhibited. These findings suggest that this new lignan glycoside from Calotropis gigantea, may have therapeutic potential in influenza virus infection through inhibition of NF-κB pathway and viral ribonucleoproteins nuclear export.

Effect of anhydrosophoradiol-3-acetate of Calotropis gigantea (Linn.) flower as antitumoric agent against Ehrlich's ascites carcinoma in mice

BACKGROUND

Over 60% of currently used anti-cancer agents are derived in one-way or another from natural sources, including plants, marine organisms and microorganisms. Calotropis gigantea (Linn.) (Family: Asclepiadaceae) is a perennial shrub and it is used as a traditional folk medicine for the treatment of various health complications. But there is no report on isolation of anticancerous chemicals from the flower of Calotropis gigantea. The objective of the present study is to explore the antitumor effect of anhydrosophoradiol-3-acetate (A3A), isolated from the flower of Calotropis gigantea (Linn.) against Ehrlich's ascites carcinoma (EAC) in Swiss albino mice.

METHODS

Antitumoric effect of A3A was assessed by evaluating viable tumor cell count, survival time, body weight gain due to tumor burden, hematological and biochemical (glucose, cholesterol, triglyceride, blood urea, SALP, SGPT and SGOT) parameters of EAC bearing host at doses of 10 and 20 mg/kg body weight.

RESULTS

Treatment with A3A decreased the viable tumor cells and body weight gain thereby increasing the life span of EAC bearing mice. A3A also brought back the altered hematological (Hb, total RBC and total WBC) and biochemical parameters more or less to normal level.

CONCLUSION

Results of this study conclude that in vivo the A3A was effective in inhibiting the growth of EAC with improving in cancer induced complications.

2'-Epi-uscharin from the latex of Calotropis gigantea with HIF-1 inhibitory activity

Two stereoisomeric cardenolides, uscharin (1) and a new compound, 2′-epi-uscharin (2), were isolated from the latex of Calotropis gigantea (Asclepiadaceae). Their structures were fully elucidated based on their spectroscopic data, X-ray crystallographic data and chemical evidences. Both epimers (1 and 2) exhibited strong inhibitory effects on HIF-1 activity with different magnitudes. Compound 1 showed much more potent activity than 2 and digoxin, a well-known HIF-1 inhibitor. Discrepancy in potencies between 1 and 2 revealed the contribution of a β-configuration of 2′ hydroxyl moiety for HIF-1 inhibitory activity. This is a first report of the activity of HIF-1 inhibition of thiazoline ring-containing cardenolides.

Calotropis gigantiea (L.) R. Br (Apocynaceae): a phytochemical and pharmacological review

ETHNOPHARMACOLOGICAL RELEVANCE

Calotropis gigantiea (L.) R. Br (Apocynaceae) commonly called as "crown flower" or "giant milk weed" is a well-known weed to many cultures for treating various disorders related to central nervous system, skin diseases, digestive system, respiratory system, reproductive system etc. Indigenous groups made the plant as a part of their lives since they use the fruit fibre to make ropes, household items, for weaving clothes and flowers for garlands apart from usage for various indications. The study aims at far-reaching review on phytochemistry, pharmacological activities, ethnopharmacology, intellectual property transfer on pharmacological therapies, toxicity which aids to provide scientific evidence for the ethnobotanical claims and to identify gaps required to be conducted as a future research prerequisite.

MATERIALS AND METHODS

A systematic literature search was performed using different databases such as Scopus, Science direct, PubMed and Sciverse with no timeline limit set during the search. All the available abstracts and full text articles were included in the systematic review.

RESULTS

Most of the folkloric uses were validated by the scientific studies such as analgesic, anti-arthritic, anti-asthmatic, anti-bacterial, anti-convulsant, anti-pyretic, central nervous system disorders, contraceptive, anti-ulcer and wound healing. In addition other studies such as anti-diabetic, anti-diarrhoeal, anti-helminthic, anti-histamine, anti-inflammatory, anti-microbial, anti-oxidant, cardio-protective studies, cytotoxicity, hepatoprotectivity, fibrinolytic, mosquitocidal, nerve muscle activity, vasodilation and skeletal muscle activities were also reported for the plant. Isolated compounds such as calotropin, frugoside and 4'-O-β-D-glucopyranosyl frugoside were tested for the cytotoxicity efficacy against both human and rat cell lines out of which calotropin showed potent activity (IC50-15 ng/ml). However there were no clinical trials reported on the plant which is one of the major lacunas.

CONCLUSIONS

This review article explores the ethnopharmacological, pharmacological activities phytochemistry and intellectual rights of Cg which gives the evidence of a potent and commercial drug which up on further research leads to the most viable drug for variety of treatments. However there is further need for in-vivo studies and clinical trials on isolated phytoconstituents which will help to commercialise.

Rapid identification of calotropagenin glycosides using high-performance liquid chromatography electrospray ionisation tandem mass spectrometry

INTRODUCTION

Cardiac glycosides in Calotropis procera have therapeutic use as inhibitors of Na⁺/K⁺-ATPase to regulate heart contractions. A large amount of research attention has been received by these compounds towards their identification and structural characterisation. In order to achieve rapid identification of cardiac glycosides in phytochemical extracts a liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed involving metal cationisation by post-column addition of alkali salts for the unambiguous determination of their molecular weights.

OBJECTIVE

Identification of cardiac glycosides in Calotropis procera leaf extract.

RESULTS

Calotropagenin and its 10 glycosides were unambiguously identified. The daughter ions at m/z 387, 369, 359, 351, 341 and 323 in their MS/MS spectra were attributed to the calotropagenin aglycone unit.

CONCLUSION

High performance liquid chromatography in combination with electrospray ionization tandem mass spectrometry involving metal cationisation by post column addition of alkali salts was successfully utilised for the rapid identification of calotropagenin glycosides/derivatives in Calotropis procera extract.

Evaluation of antitumour activity of Calotropis gigantea L. root bark against Ehrlich ascites carcinoma in Swiss albino mice

OBJECTIVE

To investigate experimentally the possible antitumor effect of methanol extract (ME) of Calotropis gigantea L. (C. gigantean) root bark and its petroleum ether (PEF) and chloroform (CF) soluble fractions against Ehrlich ascites carcinoma (EAC) in Swiss albino mice.

METHODS

The effects of ME (10 and 20 mg/kg), PEF (40 and 80 mg/kg) and CF (20 and 40 mg/kg) on the growth of EAC and life span of EAC bearing mice were studied. Hematological profile and biochemical parameters (SALP, SGPT and SGOT) were also estimated.

RESULTS

Results of in vivo study showed a significant decrease in viable tumor cell count and a significant increase of life span in the ME and CF treated group compared to untreated one. The life span of ME and CF treated animals was significantly (P<0.05) increased by 43.90% (20 mg ME/kg) and 57.07% (40 mg CF/kg). ME and CF brought back the hematological parameter more or less normal level. ME and CF also restored the altered levels of serum alkaline phosphatase (SALP) and serum glutamate oxaloacetate transaminase (SGOT).

CONCLUSIONS

Methanol extract (ME) of C. gigantea root bark and its chloroform soluble fraction (CF) possesses significant antitumor activity.

Cytotoxic Cardenolide and Sterols from Calotropis Gigantea

The dichloromethane extract from the leaves of Calotropis gigantea Linn. was strongly cytotoxic against non-small cell lung carcinoma (A549), colon carcinoma (HCT 116) and hepatocellular carcinoma (Hep G2), and non toxic to Chinese hamster ovary (AA8). The extract afforded uscharin (1), 3,5,8-trihydroxy-24-methylcholest-6,22-diene (2), a mixture of (24R)-3β-hydroxy-24-ethylcholest-5-en-7-one (3a) and 6β-hydroxy-24-ethylcholest-4,22-dien-3-one (3b), and another mixture of (24R)-24-ethylcholest-4-en-3-one (4a) and (24S)-24-ethylcholest-4,22-dien-3-one (4b). Cardenolide 1 exhibited extreme toxicity to A549, HCT 116 and Hep G2 with IC50 values of 0.003 μg/mL, 0.013 μg/mL, and 0.018 μg/mL, respectively, while sample 3 exhibited an IC50 of 1.35 μg/mL, 4.46 μg/mL, and 3.83 μg/mL, respectively.

Antimicrobial and Cytotoxic Activity of Di-(2-ethylhexyl) Phthalate and Anhydrosophoradiol-3-acetate Isolated from Calotropis gigantea (Linn.) Flower

A phytochemical study on the flowe r of Calotropis gigantea (Linn.) using silica gel column chromatography and preparative thin layer chromatography, led to the first time isolation of Di-(2-ethylhexyl) phthalate (compound 1) and anhydrosophoradiol-3-acetate (compound 2). The structures of these compounds were confirmed by spectroscopic analyses (IR, HRTOFMS and NMR). The antibacterial and antifungal activities of ethyl acetate extract, compound 1 and compound 2 were measured using the disc diffusion method. Ethyl acetate extract and compound 1 presented better results than compound 2. The minimum inhibitory concentrations (MICs) of the extract and compounds were found to be in the range of 16~128 µg/ml. The cytotoxicity (LC50) against brine shrimp nauplii (Artemia salina) were also evaluated and found to be 14.61 µg/ml for ethyl acetate, 9.19 µg/ml for compound 1 and 15.55 µg/ml for compound 2.

A new cytotoxic pregnanone from Calotropis gigantea

A new pregnanone, named calotropone (1), was isolated from the EtOH extract of the roots of Calotropis gigantea L. together with a known cardiac glycoside. The structures were elucidated by a study of their physical and spectral data. Compounds 1 and 2 displayed inhibitory effects towards chronic myelogenous leukemia K562 and human gastric cancer SGC-7901 cell lines.

Isolation of stigmasterol and beta-sitosterol from methanolic extract of root bark of Calotropis gigantea (Linn)

Aim of this study is to identify and characterize the bioactive principles from the root bark of Calotropis gigantea. It has wide folk medicinal use. For isolation of the compounds, the dried root bark's powder of Calotropis gigantea were subjected to hot extraction and then the crude methanol (MeOH) extract was fractionated with petroleum ether, chloroform and ethyl acetate. Two compounds were isolated and purified from petroleum ether fraction of crude methanol extract and the structures were determined as stigmasterol and beta-sitosterol by analysis of physical, chemical and spectral characteristics (1D NMR and mass spectrometry).

19-Nor- and 18,20-epoxy-cardenolides from the leaves of Calotropis gigantea

Two new cardenolides (1 and 2) along with 12 known compounds were isolated from the dichloromethane extract of the leaves of Calotropis gigantea. The structural elucidation was accomplished by spectroscopic methods. Some of the isolates were evaluated for cytotoxic activity against KB, BC, and NCI-H187 cancer cell lines, and all cardenolides tested were found to possess strong inhibitory effects. The presence of a deoxysugar at C-3, a formyl group at C-10, and an alpha,beta-unsaturated gamma-lactone was crucial for cytotoxic activity.

Synthesis of 2-[4'-(ethylcarbamoyl)phenyl]-N-acetylglycine, the proposed structure for giganticine

A compound (1) with the structure proposed for giganticine, an antifeedant principle isolated from the root bark of Caloropis gigantea, has been successfully synthesized by two independent methods. Comparison of physical properties and spectroscopic data of 1 with giganticine revealed that they are different compounds. All available evidence suggests that the proposed structure of giganticine is incorrect.

Development-inhibiting activity of some tropical plants against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Thirteen tropical plants were evaluated for development-inhibiting activity against Sitophilus zeamais. The bioassays were carried out by incorporating seeds or leaves at various dose levels into an artificial diet for the test insect. It was found that seeds of Basella alba and leaves of Operculina turpethum and Calotropis gigantea were potent in delaying development and in reducing adult emergence, and hence the capacity for population increase. At 0.5% concentration, adult emergence in tests with B. alba, O. turpethum and C. gigantea was reduced by 62, 95 and 70%, respectively. In B. alba and C. gigantea, the development periods were 2.2 and 1.8 times those in the control and the capacities for increase/day were only 0.0324 and 0.0328 compared with 0.1004 in the control. B. alba, O. turpethum and C. gigantea were active at concentrations as low as 0.01, 0.05 and 0.1%. The potential of these materials in insect pest management is discussed.