Overview of Silibinin anti-tumor effects

In Vivo and Clinical Studies of Natural Products Targeting the Hallmarks of Cancer

Despite more than 200 approved anticancer agents, cancer remains a leading cause of death worldwide due to disease complexity, tumour heterogeneity, drug toxicity, and the emergence of drug resistance. Accordingly, the development of chemotherapeutic agents with higher efficacy, a better safety profile, and the capability of bypassing drug resistance would be a cornerstone in cancer therapy. Natural products have played a pivotal role in the field of drug discovery, especially for the pharmacotherapy of cancer, infectious, and chronic diseases. Owing to their distinctive structures and multiple mechanistic activities, natural products and their derivatives have been utilized for decades in cancer treatment protocols. In this review, we delve into the potential of natural products as anticancer agents by targeting cancer's hallmarks, including sustained proliferative signalling, evading growth suppression, resisting apoptosis and cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis. We highlight the molecular mechanisms of some natural products, in vivo studies, and promising clinical trials. This review emphasizes the significance of natural products in fighting cancer and the need for further studies to uncover their fully therapeutic potential.

Anticancer Drug Discovery Based on Natural Products: From Computational Approaches to Clinical Studies

Globally, malignancies cause one out of six mortalities, which is a serious health problem. Cancer therapy has always been challenging, apart from major advances in immunotherapies, stem cell transplantation, targeted therapies, hormonal therapies, precision medicine, and palliative care, and traditional therapies such as surgery, radiation therapy, and chemotherapy. Natural products are integral to the development of innovative anticancer drugs in cancer research, offering the scientific community the possibility of exploring novel natural compounds against cancers. The role of natural products like Vincristine and Vinblastine has been thoroughly implicated in the management of leukemia and Hodgkin's disease. The computational method is the initial key approach in drug discovery, among various approaches. This review investigates the synergy between natural products and computational techniques, and highlights their significance in the drug discovery process. The transition from computational to experimental validation has been highlighted through in vitro and in vivo studies, with examples such as betulinic acid and withaferin A. The path toward therapeutic applications have been demonstrated through clinical studies of compounds such as silvestrol and artemisinin, from preclinical investigations to clinical trials. This article also addresses the challenges and limitations in the development of natural products as potential anti-cancer drugs. Moreover, the integration of deep learning and artificial intelligence with traditional computational drug discovery methods may be useful for enhancing the anticancer potential of natural products.

Design, Synthesis and Biological Evaluation of Glycosylated Derivatives of Silibinin as Potential Anti-Tumor Agents

Objective

Silibinin, a natural product extracted from the seeds of the Silybum marianum, is versatile with various pharmacological effects. However, its clinical application was strongly hampered by its low bioavailability and poor water solubility. Herein, a series of glycosylated silibinin derivatives were identified as novel anti-tumor agents.

Materials and Methods

The cell viability was evaluated by CCK8 assay. Furthermore, cell apoptosis and cell cycle progression were tested by flow cytometry. In addition, the pharmacokinetic assessment of compound 15 and silibinin through intravenous administration (i.v., 2 mg/kg) to ICR mice were performed.

Results

The synthesized compounds showed better water solubilities than silibinin. Among them, compound 15 exhibited inhibitory activity against DU145 cells with IC₅₀ value of 1.37 ± 0.140 μM. Moreover, it arrested cell cycle at G2/M phase and induced apoptosis in DU145 cells. Additionally, compound 15 also displayed longer half-life (T_1/2 = 128.3 min) in liver microsomes than that of silibinin (T_1/2 = 82.5 min) and appropriate pharmacokinetic parameters in mice.

Conclusion

Overall, glycosylation of silibinin would be a valid strategy for the development of silibinin derivatives as anti-tumor agents.

Pharmacological screening of silibinin for antischizophrenic activity along with its acute toxicity evaluation in experimental animals

Silibinin (SIL), a flavolignan extracted from the medicinal plant "silybum marianum (milk thistle)", has traditionally been used to treat liver disease. This phytochemical has displayed neuroprotective properties, its activity against schizophrenia is not elucidated. The present study was designed to evaluate the antipsychotic potential of silibinin and probe its toxic potential. The acute oral toxicity study was assessed as per OECD 425 guidelines. Animals were divided into two groups of female rats (n = 6): one group served as the normal control and the other group received a 2,000 mg/kg dose of SIL. We also evaluated the antipsychotic potential of SIL. To this end, animals were divided into six groups (n = 10) of mice for both the preventive and curative protocols. Group I (CMC 1 mL/kg) served as the normal control and received CMC 1 mL/kg; group II was the diseased group treated with ketamine (10 mg/kg) i.p; group III was the standard group treated with clozapine 1 mg/kg; groups IV, V, and VI served as the treatment groups, receiving SIL 50, 100, and 200 mg/kg, respectively, orally for both protocols. Improvement in positive symptoms of the disease was evaluated by stereotypy and hyperlocomotion, while negative symptoms (behavioral despair) were determined by a forced swim test and a tail suspension test in the mice models. The results suggested that the LD₅₀ of SIL was greater than 2,000 mg/kg. Moreover, SIL prevented and reversed ketamine-induced increase in stereotypy (p < 0.001) and behavioral despair in the forced swim and tail suspension tests (p < 0.001). Taken together, the findings suggest that silibinin is a safe drug with low toxicity which demonstrates significant antipsychotic activity against the positive and negative symptoms of schizophrenia.

Polypeptide induced perylene probe excimer formation and its application in the noncovalent ratiometric detection of matrix metalloproteinase activity

Matrix metalloproteinases (MMPs) are important biomarkers for a number of diseases. Thus, the precise determination of MMP activity is of crucial importance. Herein, we report a ratiometric fluorescence method for the sensitive and selective sensing of MMP activity. A number of positively charged MMP substrates (polypeptides) were designed and prepared. These polypeptides could induce aggregation of a negatively charged perylene diimide derivative (PC1). As a result, excimer fluorescence of PC1 was observed. Addition of the corresponding MMP resulted in cleavage of the polypeptide chain and dis-aggregation of PC1, which led to turning on of the PC1 monomer fluorescence. Based on the ratio of the monomer (545 nm, I_M) and the excimer (680 nm, I_M) fluorescence intensity changes, a ratiometric method I₅₄₅/I₆₈₀) was established to detect MMP activity. The enzymatic activity of a number of MMPs (MMP-1, 2, 3, 7, 9 and 13) could be determined with a limit of detection of 4.8, 2.2, 16, 6.0, 1.7 and 5.5 ng mL^-1, respectively. Using MMP-2 and MMP-9 as examples, flavonoid herbal extracts as potential inhibitors were studied. It was observed that mangiferin, apigenin, quercetin and isoliquiritigenin had significant inhibiting effects on the enzyme activity. And these herbal extracts also inhibited tumor cell metastasis. Moreover, the developed strategy was also employed to determine the concentration of MMP-9 in human saliva samples. Since the method relies on only noncovalent interactions between the polypeptide and PC1, no covalent labeling of fluorescence dye on the polypeptide substrate is required, and the method is thus simple, broad-spectrum inexpensive and effective. It has the potential to be developed into a clinical test kit.

New Insights Toward Nanostructured Drug Delivery of Plant-Derived Polyphenol Compounds: Cancer Treatment and Gene Expression Profiles

The increasing prevalence of cancer has led to the expansion of traditional medicine objectives for developing novel drug delivery systems. A wide range of plant-derived polyphenol bioactive substances have been investigated in order to explore anti-cancer effects of these natural compounds and to promote effective treatment of cancer through apoptosis induction. In this regard, plant-derived polyphenol compounds including curcumin, silibinin, quercetin, and resveratrol have been the subject of intense interest for anti-cancer applications due to their ability in regulating apoptotic genes. However, some limitations of pure polyphenol compounds, such as poor bioavailability, short-term stability, low-cellular uptake, and insufficient solubility, have restricted their efficiency. Nanoscale formulations of bioactive agents have provided a novel platform to address these limitations. This paper reviews recent advances in nanoformulation approaches of polyphenolic drugs, and their effects on improving the delivery of chemotherapy agents to cancer cells.

Targeting the pH Paradigm at the Bedside: A Practical Approach

The inversion of the pH gradient in malignant tumors, known as the pH paradigm, is increasingly becoming accepted by the scientific community as a hallmark of cancer. Accumulated evidence shows that this is not simply a metabolic consequence of a dysregulated behavior, but rather an essential process in the physiopathology of accelerated proliferation and invasion. From the over-simplification of increased lactate production as the cause of the paradigm, as initially proposed, basic science researchers have arrived at highly complex and far-reaching knowledge, that substantially modified that initial belief. These new developments show that the paradigm entails a different regulation of membrane transporters, electrolyte exchangers, cellular and membrane enzymes, water trafficking, specialized membrane structures, transcription factors, and metabolic changes that go far beyond fermentative glycolysis. This complex world of dysregulations is still shuttered behind the walls of experimental laboratories and has not yet reached bedside medicine. However, there are many known pharmaceuticals and nutraceuticals that are capable of targeting the pH paradigm. Most of these products are well known, have low toxicity, and are also inexpensive. They need to be repurposed, and this would entail shorter clinical studies and enormous cost savings if we compare them with the time and expense required for the development of a new molecule. Will targeting the pH paradigm solve the "cancer problem"? Absolutely not. However, reversing the pH inversion would strongly enhance standard treatments, rendering them more efficient, and in some cases permitting lower doses of toxic drugs. This article's goal is to describe how to reverse the pH gradient inversion with existing drugs and nutraceuticals that can easily be used in bedside medicine, without adding toxicity to established treatments. It also aims at increasing awareness among practicing physicians that targeting the pH paradigm would be able to improve the results of standard therapies. Some clinical cases will be presented as well, showing how the pH gradient inversion can be treated at the bedside in a simple manner with repurposed drugs.

STAT3 transcription factor as target for anti-cancer therapy

STATs constitute a large family of transcription activators and transducers of signals that have an important role in many cell functions as regulation of proliferation and differentiation of the cell also regulation of apoptosis and angiogenesis. STAT3 as a member of that family, recently was discovered to have a vital role in progression of different types of cancers. The activation of STAT3 was observed to regulate multiple gene functions during cancer-like cell proliferation, differentiation, apoptosis, metastasis, inflammation, immunity, cell survival, and angiogenesis. The inhibition of STAT3 activation has been an important target for cancer therapy. Inhibitors of STAT3 have been used for a long time for treatment of many types of cancers like leukemia, melanoma, colon, and renal cancer. In this review article, we summarize and discuss different drugs inhibiting the action of STAT3 and used in treatment of different types of cancer.