An updated review of Cucurbitacins and their biological and pharmacological activities

Investigation of apoptotic effects of Cucurbitacin D, I, and E mediated by Bax/Bcl-xL, caspase-3/9, and oxidative stress modulators in HepG2 cell line

Cucurbitacins, natural compounds highly abundant in the Cucurbitaceae plant family, are characterized by their anticancer, anti-inflammatory, and hepatoprotective properties. These compounds have potential as therapeutic agents in the treatment of liver cancer. This study investigated the association of cucurbitacin D, I, and E (CuD, CuI, and CuE) with the caspase cascade, Bcl-2 family, and oxidative stress modulators in the HepG2 cell line. We evaluated the antiproliferative effects of CuD, CuI, and CuE using the MTT assay. We analyzed Annexin V/PI double staining, cell cycle, mitochondrial membrane potential, and wound healing assays at different doses of the three compounds. To examine the modulation of the caspase cascade, we determined the protein and gene expression levels of Bax, Bcl-xL, caspase-3, and caspase-9. We evaluated the total antioxidant status (TAS), total oxidant status (TOS), superoxide dismutase (SOD), glutathione (GSH), Total, and Native Thiol levels to measure cellular redox status. CuD, CuI, and CuE suppressed the proliferation of HepG2 cells in a dose-dependent manner. The cucurbitacins induced apoptosis by increasing caspase-3, caspase-9, and Bax activity, inhibiting Bcl-xL activation, causing loss of ΔΨm, and suppressing cell migration. Furthermore, cucurbitacins modulated oxidative stress by increasing TOS levels and decreasing SOD, GSH, TAS, and total and native Thiol levels. Our findings suggest that CuD, CuI, and CuE exert apoptotic effects on the hepatocellular carcinoma cell line by regulating Bax/Bcl-xL, caspase-3/9 signaling, and causing intracellular ROS increase in HepG2 cells.

Discovery and Identification of the Key Contributor to the Bitter Taste in Oriental Melon after Forchlorfenuron Application

Forchlorfenuron is a cytokinin-like plant growth regulator, which on application to oriental melon fruit often produces a bitter taste due to the accumulation of cucurbitacin. In the present study, the relationship between forchlorfenuron treatment and bitterness in oriental melon fruit was revealed by human sensory analysis coupled with highly sensitive quantitative analyses. Nine cucurbitacins as the major bitter compounds were identified in the oriental melon, with their concentration ranging from 0.001 to 32.263 mg/kg. And these cucurbitacins mainly accumulated in the peel and pedicle pulp of oriental melon fruits at maturation. Application of forchlorfenuron increased the concentration of cucurbitacin B and decreased arvenin I in total cucurbitacins for the oriental melons. Calculation of the impact of the bitter taste of these compounds based on a dose/activity relationship indicated that cucurbitacin B and arvenin I were the key contributor to the bitter taste in oriental melon fruit after high-dose forchlorfenuron application. These results are helpful in understanding the source of bitterness of oriental melon and provide a practical guide on the rational use of forchlorfenuron.

Anti-Diabetic Effects of Cucurbitacins from Ibervillea lindheimeri on Induced Mouse Diabetes

Mexico has a great tradition of using medicinal plants against diabetes. For example, species from the genus Ibervillea traditionally known as “wereque” in Mexican popular medicine have a long ethnobotanical history as anti-diabetic agents. Previous studies by our group indicated that ethyl acetate extract from Ibervillea lindheimeri (I. lindheimeri) roots reduced glucose in mice with chemically induced diabetes. In this work, the primary metabolites of the ethyl acetate extract of I. lindheimeri; 23,24-dihydrocucurbitacin D (1); 2-O-β glucopyranosyl-23,24-dihydrocucurbitacin D (2), and acetylated compounds (3) and (4) obtained from 1 and 2, respectively, were evaluated as anti-hyperglycemic agents in a murine model of chemically induced diabetes. Our results showed that cucurbitacins 1, 2, and 4 reduced glycemia in diabetic CD1 mice compared to the control diabetic group. In addition, the results suggest that compounds 1, 2, and 4 promote glucose transporter type 4 (Glut4) translocation to the plasma membrane (PM) mainly in epididymal adipose tissue (EAT), AMP-activated protein kinase (AMPK) activation in soleus muscle (SM) or dual activation of AMPK, and protein kinase B (AKT) in EAT in an insulin-independent manner when compared to controls. All results together indicate that the isolated cucurbitacins are responsible for the anti-diabetic properties of I. lindheimeri acting predominantly on adipose tissue and call attention to this species as a new source of anti-diabetic compounds.

The Mechanisms of Cucurbitacin E as a Neuroprotective and Memory-Enhancing Agent in a Cerebral Hypoperfusion Rat Model: Attenuation of Oxidative Stress, Inflammation, and Excitotoxicity

Impaired cerebral hemodynamic autoregulation, vasoconstriction, and cardiovascular and metabolic dysfunctions cause cerebral hypoperfusion (CH) that triggers pro-oxidative and inflammatory events. The sequences linked to ion-channelopathies and calcium and glutamatergic excitotoxicity mechanisms resulting in widespread brain damage and neurobehavioral deficits, including memory, neurological, and sensorimotor functions. The vasodilatory, anti-inflammatory, and antioxidant activities of cucurbitacin E (CuE) can alleviate CH-induced neurobehavioral impairments. In the present study, the neuroprotective effects of CuE were explored in a rat model of CH. Wistar rats were subjected to permanent bilateral common carotid artery occlusion to induce CH on day 1 and administered CuE (0.25, 0.5 mg/kg) and/or Bay-K8644 (calcium agonist, 0.5 mg/kg) for 28 days. CH caused impairment of neurological, sensorimotor, and memory functions that were ameliorated by CuE. CuE attenuated CH-triggered lipid peroxidation, 8-hydroxy-2′-deoxyguanosine, protein carbonyls, tumor necrosis factor-α, nuclear factor-kappaB, myeloperoxidase activity, inducible nitric oxide synthase, and matrix metalloproteinase-9 levels in brain resulting in a decrease in cell death biomarkers (lactate dehydrogenase and caspase-3). CuE decreased acetylcholinesterase activity, glutamate, and increased γ-aminobutyric acid levels in the brain. An increase in brain antioxidants was observed in CuE-treated rats subjected to CH. CuE has the potential to alleviate pathogenesis of CH and protect neurological, sensorimotor, and memory functions against CH.

Phytochemical and Antimalarial Effects of Ecballium elaterium (L.) Rich. Growing in Iran

Background: Malaria is a well-recognized parasitic disease and a serious public health problem worldwide, particularly in tropical and subtropical areas. Objectives: This study was conducted to investigate the antimalarial properties of extracts with different polarities from the various parts of Ecballium elaterium (L.) Rich. (or wild cucumber) as a perennial herbaceous plant growing in Gilan and Azerbaijan provinces of Iran. Methods: The air-dried and powdered fruits, seeds, and roots of E. elaterium were extracted using three solvents with different polarities, n-Hexane (n-Hex), dichloromethane (DCM), and methanol (MeOH). The MeOH extract of roots was subjected to fractionalizing by a C18 Sep-Pak cartridge. All extracts and fractions with different polarities were assessed for their antimalarial activity using the cell-free beta-hematin formation test, and the structural groups of the fractions were identified by Thin-Layer Chromatography (TLC). Results: According to our results, the MeOH extracts of the plant’s roots presented considerable antimalarial effects with an IC50 value of 0.124 ± 0.0002 mg/mL. Bioactivity-guided fractionation of root MeOH extract by solid phase extraction (SPE) afforded six fractions. The 20% fraction showed the most potent antimalarial effect with an IC50 value of 0.167 ± 0.002 mg/mL. Moreover, the three fractions of 80%, 60%, and 100% methanol/water demonstrated considerable antimalarial activities. Phytochemical analysis of potent fractions of E. elaterium suggested the presence of flavonoids in 20% and 60% fractions and flavonoids and triterpenoids in 80% and 100% fractions. Conclusions: According to our primary phytochemical investigation on the six SPE fractions, it is recommended to purify the active constituents of the most effective fractions and investigate their biological effects in animal models.

Antibacterial and antioxidant activities of extracts and isolated compounds from the roots extract of Cucumis prophetarum and in silico study on DNA gyrase and human peroxiredoxin 5

Background

Cucumis prophetarum is traditionally used to treat liver and lung disorders, heart failure, diarrhea, gonorrhea, skin infections, intestinal problems and cancer. In the present work, the isolation of two novel compounds along with their antibacterial and antioxidant activities is reported for the first time.

Methods

Silica gel column chromatography was applied to separate constituents of the roots of C. prophetarum. The structures of isolated compounds were established using ¹H NMR, ¹³C NMR, DEPT-135, COSY, HSQC and HMBC. Agar well diffusion, DPPH assay and ferric thiocyante methods were used for antibacterial, radical scavenging and anti-lipid peroxidation activities, respectively. AutoDock Vina open source program was used for molecular docking analysis.

Results

Evaluation of the in vitro antibacterial activity of the constituents against S. aureus, B. subtilis, E. coli and S. thyphimurium revealed that the hexane extract were active against E. coli with IZ of 15.0 ± 1.41 mm, whereas an IZ of 14.6 ± 1.70 mm for MeOH extract was observed against S. aureus. Compound 1 displayed IZ of 13.6 ± 0.94 mm against E. coli and curcurbiatin 2 showed activity against B. subtilis with IZ of 13.3 ± 0.54 mm. The molecular docking analysis showed that cucurbitacins 2 and 3 have binding energy of -6.7 and -6.9 kcal/mol, respectively. The methanol and the hexane extracts of the roots of C. prophetarum inhibited DPPH radical by 70.4 and 63.3% at 100 µg/mL, respectively. On the other hand, the methanol extract inhibited lipid peroxidation by 53.0%.

Conclusion

The present study identified five compounds from the root extracts of C. prophetarum, of which two are novel cucurbitacins (1, 2). The in vitro antibacterial activity of the hexane and methanol extracts was better than the activity displayed by the isolated compounds. This is probably due to the synergistic effects of the constituents present in the root extract. The in silico molecular docking study results showed that, compounds 2 and 3 have minimum binding energy and have good affinity toward the active pocket, thus, they may be considered as good inhibitor of DNA gyrase B. Furthermore, the “drug-likeness” and ADMET prediction of compounds 2–5 nearly showed compliance with the Lipinski rule, with good absorption, distribution, metabolism, and excretion generally. The radical scavenging and anti-lipid peroxidation activities of the extracts were better than the isolated compounds. This is attributed to the presence of phenolics and flavonoids as minor constituents in the extracts of these species. Therefore, the in vitro antibacterial activity and molecular docking analysis suggest the potential use of the isolated compounds as medicine which corroborates the traditional use of the roots of C. prophetarum.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13065-021-00758-x.

Origin, Evolution, Breeding, and Omics of Chayote, an Important Cucurbitaceae Vegetable Crop

Chayote (Sechium edule), a member of the Cucurbitaceae family, is cultivated throughout tropical and subtropical regions of the world and utilized in pharmaceutical, cosmetic and food industries because it is an excellent source of minerals, dietary fibers, protein, vitamins, carotenoids, polysaccharides, phenolic and flavonoid compounds, and other nutrients. Chayote extracts process various medicinal properties, such as anti-cardiovascular, antidiabetic, antiobesity, antiulcer, and anticancer properties. With the rapid advancements of molecular biology and sequencing technology, studies on chayote have been carried out. Research advances, including molecular makers, breeding, genomic research, chemical composition, and pests and diseases, regarding chayote are reviewed in this paper. Future exploration and application trends are briefly described. This review provides a reference for basic and applied research on chayote, an important Cucurbitaceae vegetable crop.

Metabolomic analysis of the occurrence of bitter fruits on grafted oriental melon plants

Grafting has been widely applied to melon (Cucumis melo L.) production to alleviate obstacles of continuous cropping and control soil-borne diseases. However, grafting often leads to a decline of fruit quality. For example, sometimes bitter fruits are produced on grafted plants. However, the underlying physiological mechanism still remains unclear. This study investigated the effects of different rootstocks on the taste of fruits of the Balengcui, an oriental melon cultivar, during summer production. The results showed that all grafted plants with Cucurbita maxima Duch. rootstocks produced bitter fruits, while non-grafted plants and plants grafted onto muskmelon rootstocks produced no bitter fruits. Liquid chromatography-mass spectrometry and metabonomic analysis were performed to investigate the mechanism underlying the occurrence of bitter fruits. Metabolite comparisons of fruits from plants grafted onto Ribenxuesong rootstocks both with non-grafted plants and plants grafted onto muskmelon rootstocks showed that 17 metabolites including phospholipids, cucurbitacins and flavonoids, exhibited changes. The three Cucurbitacins, Cucurbitacin O, Cucurbitacin C, and Cucurbitacin S, increased dramatically. The 10 phospholipids PS(18:1(9Z)/18:2(9Z,12Z)), PS(P-18:0/15:0), PA(18:1(11Z)/18:1(11Z)), PE(16:0/18:0), PS(O-16:0/17:2(9Z,12Z)), PI(16:0/18:2(9Z,12Z)), PA(15:0/22:6(4Z,7Z,10Z,13Z,16Z,19Z)), PS(P-16:0/17:2(9Z,12Z)), PS(22:0/22:1(11Z)), and PA(17:1(9Z)/0:0)) were significantly decreased, while two PA (16:0/18:2 (9Z, 12Z) and 16:0/18:1 (11Z)), two flavonoids (pelargonidin 3-(6''-malonylglucoside)-5-glucoside and malvidin 3-rutinoside) significantly increased in fruits of plants grafted onto Cucurbita maxima Duch. rootstocks. These metabolites were involved in the glycerophospholipid metabolic pathway, the mevalonate pathway, and the phenylpropanoid pathway. In summary, these results showed that the bitter fruits of grafted Balengcui were caused by Cucurbita maxima Duch. rootstocks. Phospholipids, cucurbitacins, and flavonoids were the key contributors for the occurrence of bitter fruits in Balengcui melon after grafting onto Cucurbita maxima Duch. rootstocks.

Isolation of anticancer constituents from Cucumis prophetarum var. prophetarum through bioassay-guided fractionation

BACKGROUND

Cucumis prophetarum var. prophetarum is used in Saudi folk medicine for treating liver disorders and grows widely between Abha and Khamis Mushait City, Saudi Arabia.

METHODS

Bioassay-guided fractionation and purification were used to isolate the main active constituents of Cucumis prophetarum var. prophetarum fruits. These compounds were structurally elucidated using NMR spectroscopy, mass spectral analyses and x-ray crystallography. All fractions, sub-fractions and pure compounds were screened for their anticancer activity against six cancer cell lines.

RESULTS

The greatest cytotoxic activity was found to be in the ethyl acetate fraction, resulting in the isolation of five cucurbitacin compounds [E, B, D, F-25 acetate and Hexanorcucurbitacin D]. Among the cucurbitacins that were isolated and tested cucurbitacin B and E showed potent cytotoxicity activities against all six human cancer cell lines.

CONCLUSION

Human breast cancer cell lines were found to be the most sensitive to cucurbitacins. Preliminary structure activity relationship (SAR) for cytotoxic activity of Cucurbitacins against human breast cancer cell line MDA-MB-231 has been reported.