Cholestane glycosides from Ornithogalum saundersiae bulbs and the induction of apoptosis in HL-60 cells by OSW-1 through a mitochondrial-independent signaling pathway

Search for new steroidal glycosides with anti-cancer potential from natural resources

Chemical investigations of higher plants, with particular attention paid to their steroidal glycosides, present a promising approach for generating anti-cancer agents from natural products. We conducted a systematic phytochemical investigation of nine higher plants-whole plants and rhizomes of Convallaria majalis, whole plants of Agave utahensis, roots of Adonis amurensis, seeds of Adonis aestivalis, bulbs of Bessera elegans, bulbs of Fritillaria meleagris, seeds of Digitalis purpurea, underground parts of Yucca glauca, and bulbs of Lilium pumilum-which led to the discovery of novel steroidal glycosides. The structures of these new constituents were determined based on spectroscopic data and chemical transformations. The identification of the monosaccharides including their absolute configurations was carried out by direct HPLC analysis of their hydrolysates using an optical rotation detector. Cytotoxicity of the isolated steroidal glycosides was evaluated against various tumor cells (A549, ACHN, HepG-2, HL-60, HSC-2, HSC-3, HSC-4, HSG, and SBC-3) and normal cells (Fa2 N-4, HK-2, and TIG-3 cells). Certain steroidal glycosides exhibit selective cytotoxicity and synergistic effects, making them potential lead compounds for use as anti-cancer agents. We document the isolation of 139 steroidal glycosides from higher plants and assessment their cytotoxic activities.

Advances in antitumor activity and mechanism of natural steroidal saponins: A review of advances, challenges, and future prospects

BACKGROUND

Cancer, the second leading cause of death worldwide following cardiovascular diseases, presents a formidable challenge in clinical settings due to the extensive toxic side effects associated with primary chemotherapy drugs employed for cancer treatment. Furthermore, the emergence of drug resistance against specific chemotherapeutic agents has further complicated the situation. Consequently, there exists an urgent imperative to investigate novel anticancer drugs. Steroidal saponins, a class of natural compounds, have demonstrated notable antitumor efficacy. Nonetheless, their translation into clinical applications has remained unrealized thus far. In light of this, we conducted a comprehensive systematic review elucidating the antitumor activity, underlying mechanisms, and inherent limitations of steroidal saponins. Additionally, we propose a series of strategic approaches and recommendations to augment the antitumor potential of steroidal saponin compounds, thereby offering prospective insights for their eventual clinical implementation.

PURPOSE

This review summarizes steroidal saponins' antitumor activity, mechanisms, and limitations.

METHODS

The data included in this review are sourced from authoritative databases such as PubMed, Web of Science, ScienceDirect, and others.

RESULTS

A comprehensive summary of over 40 steroidal saponin compounds with proven antitumor activity, including their applicable tumor types and structural characteristics, has been compiled. These steroidal saponins can be primarily classified into five categories: spirostanol, isospirostanol, furostanol, steroidal alkaloids, and cholestanol. The isospirostanol and cholestanol saponins are found to have more potent antitumor activity. The primary antitumor mechanisms of these saponins include tumor cell apoptosis, autophagy induction, inhibition of tumor migration, overcoming drug resistance, and cell cycle arrest. However, steroidal saponins have limitations, such as higher cytotoxicity and lower bioavailability. Furthermore, strategies to address these drawbacks have been proposed.

CONCLUSION

In summary, isospirostanol and cholestanol steroidal saponins demonstrate notable antitumor activity and different structural categories of steroidal saponins exhibit variations in their antitumor signaling pathways. However, the clinical application of steroidal saponins in cancer treatment still faces limitations, and further research and development are necessary to advance their potential in tumor therapy.

OSW-1 triggers necroptosis in colorectal cancer cells through the RIPK1/RIPK3/MLKL signaling pathway facilitated by the RIPK1-p62/SQSTM1 complex

BACKGROUND

Necroptosis has emerged as a novel molecular pathway that can be targeted by chemotherapy agents in the treatment of cancer. OSW-1, which is derived from the bulbs of Ornithogalum saundersiae Baker, exerts a wide range of pharmacological effects.

AIM

To explore whether OSW-1 can induce necroptosis in colorectal cancer (CRC) cells, thereby expanding its range of clinical applications.

METHODS

We performed a sequence of functional experiments, including Cell Counting Kit-8 assays and flow cytometry analysis, to assess the inhibitory effect of OSW-1 on CRC cells. We utilized quantitative proteomics, employing tandem mass tag labeling combined with liquid chromatography-tandem mass spectrometry, to analyze changes in protein expression. Subsequent bioinformatic analysis was conducted to elucidate the biological processes associated with the identified proteins. Transmission electron microscopy (TEM) and immunofluorescence studies were also performed to examine the effects of OSW-1 on necroptosis. Finally, western blotting, siRNA experiments, and immunoprecipitation were employed to evaluate protein interactions within CRC cells.

RESULTS

The results revealed that OSW-1 exerted a strong inhibitory effect on CRC cells, and this effect was accompanied by a necroptosis-like morphology that was observable via TEM. OSW-1 was shown to trigger necroptosis via activation of the RIPK1/RIPK3/MLKL pathway. Furthermore, the accumulation of p62/SQSTM1 was shown to mediate OSW-1-induced necroptosis through its interaction with RIPK1.

CONCLUSION

We propose that OSW-1 can induce necroptosis through the RIPK1/RIPK3/MLKL signaling pathway, and that this effect is mediated by the RIPK1-p62/SQSTM1 complex, in CRC cells. These results provide a theoretical foundation for the use of OSW-1 in the clinical treatment of CRC.

Steroidal glycosides from Ornithogalum thyrsoides bulbs and their cytotoxicity toward HL-60 human promyelocytic leukemia cells and SBC-3 human small-cell lung cancer cells

Ornithogalum thyrsoides Jacq belongs to the Asparagaceae family and is cultivated for ornamental purposes. The authors have previously reported several cholestane- and spirostan-type steroidal glycosides from O. thyrsoides. Conventional TLC analysis of the methanolic bulb extract of O. thyrsoides suggested the presence of unprecedented compounds; therefore, a detailed phytochemical investigation of the extract was performed and 35 steroidal glycosides (1-35), including 21 previously undescribed ones (1-21) were collected. The structures of 1-21 were determined mainly by analyses of their 1H and 13C NMR spectra with the aid of two-dimensional NMR spectroscopy. The isolated compounds were classified into three distinct groups: furostan-type (1, 2, 8-12, and 22), spirostan-type (3-7 and 23-26), and cholestane-type (13-21 and 27-35). Although the C/D-ring junction of the steroidal skeleton is typically trans-oriented, except for some cardiotonic and pregnane-type steroidal derivatives, 7 possess a cis C/D-ring junction. This is the first reported instance of such a configuration in spirostan-type steroidal derivatives, marking it as a finding of significant interest. Compounds 1-35 were evaluated for cytotoxicity against HL-60 human promyelocytic leukemia cells and SBC-3 human small-cell lung cancer cells. Compounds 3-6, 9, 17-21, 23-25, and 30-35 demonstrated cytotoxicity in a dose-dependent manner with IC50 values ranging from 0.000086 to 18 μM and from 0.00014 to 37 μM toward HL-60 and SBC-3 cells, respectively. Compound 19, which is obtained in a good yield and shows relatively potent cytotoxicity among the undescribed compounds, induces apoptosis in HL-60 cells, accompanied by arresting the cell cycle of HL-60 cells at the G2/M phase. In contrast, 19 causes oxidative stress-associated necrosis in SBC-3 cells. The cytotoxic mechanism of 19 is different between HL-60 and SBC-3 cells.

OSW-1 induces apoptosis and cyto-protective autophagy, and synergizes with chemotherapy on triple negative breast cancer metastasis

PURPOSE

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer. As yet, chemotherapy with drugs such as doxorubicin is the main treatment strategy. However, drug resistance and dose-dependent toxicities restrict their clinical use. Natural products are major sources of anti-tumor drugs. OSW-1 is a natural compound with strong anti-cancer effects in several types of cancer, but its effects on the efficacy of chemotherapy in TNBC and its underlying mechanism remain unclear.

METHODS

The inhibitory activities of OSW-1 and its combination with several chemotherapy drugs were tested using in vitro assays and in vivo subcutaneous and metastatic mouse TNBC models. The effects of the mono- and combination treatments on TNBC cell viability, apoptosis, autophagy and related signaling pathways were assessed using MTT, flow cytometry, RNA sequencing and immunology-based assays. In addition, the in vivo inhibitory effects of OSW-1 and (combined) chemotherapies were evaluated in subcutaneous and metastatic mouse tumor models.

RESULTS

We found that OSW-1 induces Ca²⁺-dependent mitochondria-dependent intrinsic apoptosis and cyto-protective autophagy through the PI3K-Akt-mTOR pathway in TNBC cells in vitro. We also found that OSW-1 and doxorubicin exhibited strong synergistic anti-TNBC capabilities both in vivo and in vitro. Combination treatment strongly inhibited spontaneous and experimental lung metastases in 4T1 mouse models. In addition, the combination strategy of OSW-1 + Carboplatin + Docetaxel showed an excellent anti-metastatic effect in vivo.

CONCLUSIONS

Our data revealed the mode of action and molecular mechanism underlying the effect of OSW-1 against TNBC, and provided a useful guidance for improving the sensitivity of TNBC cells to conventional chemotherapeutic drugs, which warrants further investigation.

Anticancer effects of OSW-1 on glioma cells via regulation of the PI3K/AKT signal pathway: A network pharmacology approach and experimental validation in vitro and in vivo

Background: Gliomas are the most common primary intracranial malignant tumors with poor prognosis, despite the remarkable advances in medical technology that have been made. OSW-1, isolated from Ornithogalum saundersiae, possesses anticancer activity against various malignant cancer cells. However, the effects of OSW-1 on gliomas and its potential mechanisms remain unclear.

Methods: Network pharmacology was employed for predicting potential key targets and mechanisms of the anticancer effects of OSW-1 on glioma. Experiments, including the Cell Counting Kit-8, colony formation, and flow cytometry, were performed to investigate how OSW-1 affects the biological behavior of glioma cells in vitro. Western blotting was used to detect changes in related proteins, such as those involved in the cell cycle, apoptosis, and signaling pathways. The nude mouse xenograft model was used to detect the effect of OSW-1 on inhibiting the proliferation of glioma cells in vivo.

Results: An “OSW-1-Targets-Glioma” intersection network consisting of 151 intersecting genes was acquired to construct a “Protein–Protein Interaction network” and predict the top 10 core targets. According to the Kyoto Encyclopedia of Genes and Genomes pathway analysis, the PI3K/AKT signaling pathway was the top 3-ranked pathway, with 38 enriched intersecting genes. The glioma T98G and LN18 cell lines were used to verify the predictions. OSW-1 significantly inhibited the viability and proliferation of glioma cells in a dose- and time-dependent manner. Flow cytometry showed that OSW-1 arrested the cell cycle at the G2/M phase, and the apoptotic ratio of glioma cells increased significantly with increasing concentrations. Western blotting revealed that the expression levels of p-PI3K and p-AKT1 in glioma cells treated with OSW-1 were significantly lower than those in the controls; however, 740Y-P, a PI3K activator, significantly reversed the inactivation of the PI3K/AKT signaling pathway caused by OSW-1. Furthermore, the mouse xenograft model confirmed the suppressive effect of OSW-1 on tumor growth in vivo.

Conclusion: OSW-1 is a promising anti-glioma chemotherapeutic drug owing to its anticancer effects via downregulation of the PI3K/AKT signaling pathway. However, OSW-1 still has a long way to go to become a real anti-glioma drug.

Selective obstruction of the mTORC2 complex by a naturally occurring cholestane saponin (OSW-1) for inhibiting prostate cancer cell growth

Ornithogalum caudatum Ait (OCA) is a natural product used in Chinese traditional medicine. The cholestane saponin OSW-1 is isolated from plant OCA and has recently been shown to have potent cytotoxic effects against different types of cancers. The therapeutic efficacy of OSW-1 on prostate cancer and its underlying mechanism are yet to be established. OSW-1 inhibited the growth of prostate cancer cells by interrupting the interaction between mTOR and Rictor/mTORC2. This mechanism showed a better therapeutic outcome than that of the conventional inhibition of mTOR and provided a basis for as sisting modern prostate cancer treatment strategies.

In vitro Cytotoxic Screening of Different Parts from Ornithogalum bungei on Selected Cancer Cells

BACKGROUND

Natural products comprise a large section of pharmaceutical agents in the field of cancer therapy. In the present study, the organic extracts and fractions of various parts of Ornithogalum bungei were investigated for in vitro cytotoxic properties on three human cancer cell lines, hepatocellular carcinoma (HepG2), prostate cancer (PC3), and leukemia (K562) cells.

METHODS

The present experimental study was conducted at Tehran University of Medical Sciences (Tehran, Iran) during 2017-2019. Separately extracted plant materials, including bulbs, stems, and flowers of O. bungei were assessed by the tetrazolium dye-based colorimetric assay (MTT). The selected extracts were submitted to fractionation using vacuum liquid chromatography and after MTT assay, the half maximal inhibitory concentration (IC₅₀ (value for each fraction was determined. The data were analyzed using One-way ANOVA followed by Tukey's post hoc test. P<0.05 was considered statistically significant.

RESULTS

The cytotoxicity of the bulb's methanol extract and the dichloromethane extract of aerial parts increased in a concentration-dependent manner. Additionally, cell viability decreased in a dose-dependent manner. In the HepG2 cell line, the best IC₅₀ values of fractions from DCM extracts of aerial parts were determined to be 19.8±10.2 µg/mL after 24 hours of exposure and 19.39±6.4 µg/mL following 48 hours of exposure. In the PC3 cell line, after 48 hours of exposure, the IC₅₀ values of fractions were unaccountable, while the percentage of inhibition for A6 to A11 in 24 hours of exposure was more than 40 µg/mL.

CONCLUSION

O. bungei growing in Iran showed significant potentials as a cytotoxic agent with selective effects on different cancer cell lines.

Structure and Cytotoxicity of Novel Lignans and Lignan Glycosides from the Aerial Parts of Larrea tridentata

Previously, the authors conducted phytochemical investigations of the aerial parts of Larrea tridentata and reported triterpene glycosides and lignan derivatives. In continuation of the preceding studies, 17 lignans and lignan glycosides (1-17) were isolated, including seven new compounds (1-7). Herein, the structure of the new compounds was determined based on spectroscopic analysis and enzymatic hydrolysis. The cytotoxicity of 1-17 against HL-60 human promyelocytic leukemia cells was examined. Compounds 4-11 and 14-16 were cytotoxic to HL-60 cells, with IC50 values in the range of 2.7-17 μM. Compound 6, which was the most cytotoxic among the unprecedented compounds, was shown to induce apoptotic cell death in HL-60 cells.

Anticancer Effects and Mechanisms of OSW-1 Isolated From Ornithogalum saundersiae: A Review

For centuries, cancer has been a lingering dark cloud floating on people's heads. With rapid population growth and aging worldwide, cancer incidence and mortality are growing rapidly. Despite major advances in oncotherapy including surgery, radiation and chemical therapy, as well as immunotherapy and targeted therapy, cancer is expected be the leading cause of premature death in this century. Nowadays, natural compounds with potential anticancer effects have become an indispensable natural treasure for discovering clinically useful agents and made remarkable achievements in cancer chemotherapy. In this regards, OSW-1, which was isolated from the bulbs of Ornithogalum saundersiae in 1992, has exhibited powerful anticancer activities in various cancers. However, after almost three decades, OSW-1 is still far from becoming a real anticancer agent for its anticancer mechanisms remain unclear. Therefore, in this review we summarize the available evidence on the anticancer effects and mechanisms of OSW-1 in vitro and in vivo, and some insights for researchers who are interested in OSW-1 as a potential anticancer drug. We conclude that OSW-1 is a potential candidate for anticancer drugs and deserves further study.

SANCDB: an update on South African natural compounds and their readily available analogs

BACKGROUND

South African Natural Compounds Database (SANCDB; https://sancdb.rubi.ru.ac.za/ ) is the sole and a fully referenced database of natural chemical compounds of South African biodiversity. It is freely available, and since its inception in 2015, the database has become an important resource to several studies. Its content has been: used as training data for machine learning models; incorporated to larger databases; and utilized in drug discovery studies for hit identifications.

DESCRIPTION

Here, we report the updated version of SANCDB. The new version includes 412 additional compounds that have been reported since 2015, giving a total of 1012 compounds in the database. Further, although natural products (NPs) are an important source of unique scaffolds, they have a major drawback due to their complex structure resulting in low synthetic feasibility in the laboratory. With this in mind, SANCDB is, now, updated to provide direct links to commercially available analogs from two major chemical databases namely Mcule and MolPort. To our knowledge, this feature is not available in other NP databases. Additionally, for easier access to information by users, the database and website interface were updated. The compounds are now downloadable in many different chemical formats.

CONCLUSIONS

The drug discovery process relies heavily on NPs due to their unique chemical organization. This has inspired the establishment of numerous NP chemical databases. With the emergence of newer chemoinformatic technologies, existing chemical databases require constant updates to facilitate information accessibility and integration by users. Besides increasing the NPs compound content, the updated SANCDB allows users to access the individual compounds (if available) or their analogs from commercial databases seamlessly.

A Total of Eight Novel Steroidal Glycosides Based on Spirostan, Furostan, Pseudofurostan, and Cholestane from the Leaves of Cestrum newellii

Previously, various steroidal glycosides were reported from plants of Cestrum species. However, phytochemical investigation has not been conducted on Cestrum newellii. A systematic phytochemical investigation of the leaves of C. newellii resulted in the isolation of eight novel steroidal glycosides (1-8), which were classified into three spirostanol glycosides (1-3), two furostanol glycosides (4 and 5), two pseudofurostanol glycosides (6 and 7), and one cholestane glycoside (8). In addition, three known cholestane glycosides (9-11) were isolated and identified. The structures of the new compounds were determined based on spectroscopic data and chemical transformations. Compounds 1 and 2 are spirostanol glycosides having hydroxy groups at C-2, C-3, C-12, and C-24 of the aglycone moiety. Although C. newellii is known to be a poisonous plant, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay exhibited that none of the isolated compounds were cytotoxic to HL-60 human promyelocytic leukemia cells.