Standardized phytopreparations and cucurbitacin IIb from Ibervillea sonorae (S. Watson) greene induce apoptosis in cervical cancer cells by Nrf2 inhibition

ETHNOPHARMACOLOGY RELEVANCE

Ibervillea sonorae (S. Watson) Greene is a plant from northwestern Mexico, known as "Wereke" or "Guareque", used by the Mayo ethnic group to treat diabetes and cancer. Cucurbitacin IIb (CIIb), isolated from I. sonorae has apoptotic and antitumor activity in a model of cervical cancer with the HeLa cell line. One pathway affected by cucurbitacins is Nrf2, a glutathione transferase (GST) transcription factor, important in the regulation of mitochondrial oxidative stress (MOS). A signal of MOS is the change in the mitochondrial membrane potential (ΔΨm), which has been detected in HeLa in the presence of CIIb. Fito-Ison-EtOH (Etanison) and Fito-Ison-EtOAc (Acetison) are phytopreparations from I. sonorae standardized according to their CIIb content (6.7 mg/g and 18.4 mg/g of CIIb, respectively). Etanison and Acetison have been reported to induce morphological changes in HeLa like those induced by CIIb.

AIM OF THE STUDY

To evaluate the apoptotic and Nrf2 inhibition activity of the phytopreparations Acetison and Etanison from Ibervillea Sonorae in the HeLa cervical cancer cell line.

MATERIALS AND METHODS

Antiproliferative activity was evaluated by the MTT method at 24, 48, and 72 h. For Acetison and Etanison, serial concentrations from 6.25 μg/mL to 100 μg/mL were tested, and for CIIb from 1.56 μg/mL to 50 μg/mL. The expression of Nrf2, caspase 3, and caspase 9 was evaluated by western blot, using concentrations of 30 μg/mL for Acetison, 50 μg/mL for Etanison, and 15 μg/mL for CIIb. Cisplatin was used as a positive control.

RESULTS AND CONCLUSIONS

Apoptotic activity of Etanison and Acetison was demonstrated in HeLa, due to the presence of caspase-9 and caspase-3 in western blot assays. Likewise, both the phytopreparations and CIIb showed inhibition of Nrf2, associating apoptotic activity with the inhibition of the GST transcription factor. In this sense, the phytopreparations of I. sonorae, as well as their derivatives, have the potential to obtain and develop anticancer products.

In Vitro Antitumor Activity of Endophytic and Rhizosphere Gram-Positive Bacteria from Ibervillea sonorae (S. Watson) Greene against L5178Y-R Lymphoma Cells

Plant-associated microorganisms represent a potential source of new antitumor compounds. The aim of the present study was to isolate endophytic and rhizosphere Gram-positive bacteria from Ibervillea sonorae and produce extracts with antitumor activity. Methanol and ethyl acetate extracts were obtained from 28 d bacterial fermentation, after which murine L5178Y-R lymphoma cells growth inhibition was evaluated at concentrations ranging from 15.62 µg/mL to 500 µg/mL by the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide reduction colorimetric assay. IC₅₀ and the selectivity index (SI) were calculated and compared with healthy control human peripheral blood mononuclear cells (PBMC). Identification of the isolated strains was performed using the 16S ribosomal gene and by MALDI-TOF MS mass spectrometry. The endophytic and rhizosphere bacterial extracts from strains ISE-B22, ISE-B26, ISE-B27, ISS-A01, ISS-A06, and ISS-A16 showed significant (p < 0.05) L5178Y-R cell growth inhibition, compared with an untreated control. The rhizosphere Micromonospora echinospora isolate ISS-A16 showed the highest (90.48%) percentage of lymphoma cells growth inhibition and SI (19.1) for PBMC, whereas the Bacillus subtilis ISE-B26 isolate caused significant (p < 0.01) growth inhibition (84.32%) and a SI of 5.2. Taken together, results of the present study evidenced antitumor effects by I. sonorae endophytic and rhizosphere bacteria culture extracts. Further research will involve the elucidation of the compounds that exert the antitumor activity and their evaluation in pre-clinical studies.

Antiproliferative activity of standardized phytopreparations from Ibervillea sonorae (S. Watson) Greene

Ibervillea sonorae (Cucurbitaceae) is a medicinal plant utilized in Northwest Mexico against Diabetes and cancer. This natural product is taken orally, its presentation is capsules containing the plant's dried and powdered caudices. There is no regulation or standardized dosage that allows reproducibility of its pharmacological effects. Cucurbitacins are the main group of compounds found in I. sonorae and are known for their antiproliferative activity in cancer cells. Cucurbitacin IIb (CIIb), one of the compounds present in I. sonorae, has demonstrated in experimental models with HeLa cervical cancer cells an apoptotic and anti-tumoral activity. The objective of this study is to obtain and standardize two phytopreparations of I. sonorae based on their CIIb content, evaluate their antiproliferative activity in cancer cell lines, and compare the results with those obtained with CIIb; expecting to find phytopreparations with anti-cancer potential. APCI-IT-MSn is utilized for the identification of cucurbitacins, FT-ICR-MS/MS for the quantification of CIIb, and the MTT assay for the evaluation of the antiproliferative activity. The CIIb content was 0.67% for Fito-Ison-EtOH and 1.84% for Fito-Ison-EtOAc. In both phytopreparations, six cucurbitacins have been identified, and a seventh one not previously identified. Phytopreparations were more effective against HeLa, with IC₅₀ of 30.0 and 18.6 µg/mL for Fito-Ison-EtOH and Fito-Ison-EtOAc, respectively. This effect is lower than observed on CIIb in HeLa (5.8 µg/mL). There are no significant differences (p > 0.05) in the antiproliferative activity between Fito-Ison-EtOAc and CIIb in A549, LS180, and MDA-MB-231 cells. Phytopreparations of I. sonorae have potential for the development of anti-cancer products.

Quantitative analysis of cucurbitane-type triterpenes in Ibervillea sonorae extracts: Relationship study with their antiproliferative activity

Ibervillea sonorae (Cucurbitaceae) is a Mexican plant commonly used by local population for its hypoglycaemic activity. Root extracts showed also other different biological activities, including antimicrobial, antifungal, antioxidant and anti-inflammatory activity. Main components of this plant are cucurbitacins, steroid-like triterpenes that possess, among others, antiproliferative activity. In previous studies, kinoin A and cucurbitacin IIb extracted from I. sonorae showed antiproliferative and apoptotic effects against different cancer cell lines. Based on all the above, a RP-HPLC method was developed and validated for the quantitative analysis of these two compounds in I. sonorae root extracts obtained with different extraction conditions. In the present study, the quantitative analysis of kinoin B diglycoside in all the extracts was performed as well. As a result, no direct correlation was found between the antiproliferative activity (IC₅₀) against human cervical cancer cell line (HeLa) and the composition of the above three compounds. Only a slight statically significant negative correlation was observed between IC_50s and the content of kinoin A (r = 0.29, p = 0.12), meaning that, at least in part, this is the main compound among the three, contributing to the antiproliferative activity on the real samples. Accordingly, a synergistic effect by the phytocomplex components can account for the observed antiproliferative activity of the methanolic extracts towards HeLa cells.

Cucurbitacin IIb, a steroidal triterpene from Ibervillea sonorae induces antiproliferative and apoptotic effects on cervical and lung cancer cells

Chemical studies on Ibervillea sonorae (S. Watson) Greene root led to isolation and chemical characterization of diverse cucurbitacin triterpenoid compounds such as kinoin A, B, C, and their glucosides. In previous studies, we demonstrated that kinoin A inhibits the cell proliferation on diverse cell line and induce apoptosis in HeLa cells. Therefore, the study of the isolated compounds from the extracts continued to be necessary. The objective of the present work was to isolate and chemically characterize the active compounds of the methanolic extract of the roots of I. sonorae and to evaluate their antiproliferative activity and induction of apoptosis. By chromatographic column separation and using NMR spectroscopy experiments, cucurbitacin IIb (CIIb), known as 23,24-dihydrocucurbitacin F or hemslecin B, was isolated and identified for the first time as a chemical constituent of the crude methanolic extract of this plant. The antiproliferative activity of CIIb was evaluated by MTT assay, and the apoptosis induction capacity was monitored by annexin V-FITC/propidium iodide using flow cytometry. CIIb showed a pronounced effect on the proliferation of HeLa and A549 tumor cells, with IC₅₀ of 7.3 and 7.8 µM, respectively, but was less effective against L929 non-cancerous murine cell line. Apoptosis induction capacity of CIIb on HeLa and A549 was monitored by annexin V-FITC/propidium iodide using flow cytometry. Exposure of HeLa and A549 with CIIb (8 µM) for 24 h increased 56.9 and 52.3% respectively of the total apoptosis compared to the negative control (p < 0.005). CIIb, isolated for the first time from I. sonorae, showed antiproliferative activity against HeLa and A549 cell lines by inducing cell death by apoptosis.