Antioxidant conjugated metal complexes and their medicinal applications

Antioxidants are naturally available and man-made substances have the ability to protect cells from damage due to a number of intracellular redox activities. Moreover, Antioxidants such as α-lipoic acid, curcumin and catechin are good anticancer agents. In recent years, the usage of metal complexes as therapeutic agents is gaining importance due to their useful biological properties. Most of the metal ions act as the essential components in building drug molecules that serve as medicines for cancer and neurodegenerative diseases. In particular, metals like copper, gold, ruthenium, and platinum have adequate anticancer properties at both micro- and nano-levels. Hence, conjugation of antioxidants with metals and metal-based compounds results in hybrid bioactive materials with improved anticancer properties. In this chapter, medicinal applications of antioxidant conjugated metal complexes are reviewed and discussed.

Crosstalk between xanthine oxidase (XO) inhibiting and cancer chemotherapeutic properties of comestible flavonoids- a comprehensive update

Gout is an inflammatory disease caused by metabolic disorder or genetic inheritance. People throughout the world are strongly dependent on ethnomedicine for the treatment of gout and some receive satisfactory curative treatment. The natural remedies as well as established drugs derived from natural sources or synthetically made exert their action by mechanisms that are closely associated with anticancer treatment mechanisms regarding inhibition of xanthine oxidase, feedback inhibition of de novo purine synthesis, depolymerization and disappearance of microtubule, inhibition of NF-ĸB activation, induction of TRAIL, promotion of apoptosis, and caspase activation and proteasome inhibition. Some anti-gout and anticancer novel compounds interact with same receptors for their action, e.g., colchicine and colchicine analogues. Dietary flavonoids, i.e., chrysin, kaempferol, quercetin, fisetin, pelargonidin, apigenin, luteolin, myricetin, isorhamnetin, phloretinetc etc. have comparable IC₅₀ values with established anti-gout drug and effective against both cancer and gout. Moreover, a noticeable number of newer anticancer compounds have already been isolated from plants that have been using by local traditional healers and herbal practitioners to treat gout. Therefore, the anti-gout plants might have greater potentiality to become selective candidates for screening of newer anticancer leads.

Antioxidant and Anticancer Activities and Protein Interaction of the Oxidovanadium(IV) Naringin Complex

The complex of oxidovanadium(IV) with naringin (Narg) [VO(Narg)2] 8H2O (VONarg) was prepared according to the literature improving the synthetic procedure and physicochemical characterization. In addition, biological activities (cytotoxic, antioxidant, and BSA interaction) were determined. The metal coordinated through the 5-hydroxy and 4-carbonyl groups of rings A and C of naringin, respectively. The antioxidant activity of VONarg, determined in vitro, was higher than those of the flavonoid against superoxide and peroxyl reactive oxygen species (ROS) and DPPH radical. The cytotoxic properties were determined by a MTT assay on adenocarcinoma human alveolar basal epithelial cells (A549). VONarg exerted a 20% decrease in cancer cells viability at 24 h incubation, while naringin and oxidovanadium(IV) cation did not show cytotoxicity. Measurements with the normal HEK293 cell line showed that the inhibitory action of the complex is selective. VONarg generated intracellular reactive oxygen species (ROS), depletion of reduced glutathione and depolarization of mitochondrial membrane potential, typical for apoptotic pathway, producing cell death by oxidative stress mechanism. Moreover, naringin interacted with bovine serum albumin (BSA) through hydrophobic interactions in a spontaneous process, and VONarg showed greater affinity for the protein but can still be transported and delivered by it (Ka 104 L·mol−1 order).

Study on the cytotoxic, antimetastatic and albumin binding properties of the oxidovanadium(IV) chrysin complex. Structural elucidation by computational methodologies

We have previously synthesized and characterized the chrysin coordination complex with the oxidovanadium(IV) cation (V^IVO(chrys)₂) and characterized in ethanolic solution and in solid state. Because suitable single crystals for X-ray diffraction determinations could not be obtained, in the present work, we elucidate the geometrical parameters of this complex by computational methodologies. The optimization and vibrational investigation were carried out both in ethanolic solution and in gas phase. The computational results support the experimentally proposed geometries of the V^IVO(chrys)₂ complex, thus leading to the conclusion that the complex exists as conformers with trans-octahedral geometry in ethanolic solution and as conformers with cis-octahedral geometry in the solid state. The complex also exists as conformers with trans-octahedral geometry in aqueous media. The active species formed after dissolution in DMSO showed anticancer and antimetastatic behavior in human lung cell line A549 with moderate binding (K_aca. 10⁵ M^-1) to bovine serum albumin (BSA). The interaction through hydrogen bonding and van der Waals forces resulted in a spontaneous process. Site marker competitive experiments showed binding sites for chrysin mainly located in site II (subdomain IIIA) and in site I (subdomain IIIA) for the complex. FT-IR spectral measurements showed evidences of the alterations of protein secondary structure in the presence of chrysin and V^IVO(chrys)₂.

Rutin (Bioflavonoid) as Cell Signaling Pathway Modulator: Prospects in Treatment and Chemoprevention

Cancer is a complex ailment orchestrated by numerous intrinsic and extrinsic pathways. Recent research has displayed a deep interest in developing plant-based cancer therapeutics for better management of the disease and limited side effects. A wide range of plant-derived compounds have been reported for their anticancer potential in the quest of finding an effective therapeutic approach. Rutin (vitamin P) is a low-molecular weight flavonoid glycoside (polyphenolic compound), abundantly present in various vegetables, fruits (especially berries and citrus fruits), and medicinal herbs. Numerous studies have delineated several pharmacological properties of rutin such as its antiprotozoal, antibacterial, anti-inflammatory, antitumor, antiviral, antiallergic, vasoactive, cytoprotective, antispasmodic, hypolipidemic, antihypertensive, and antiplatelet properties. Specifically, rutin-mediated anticancerous activities have been reported in several cancerous cell lines, but the most common scientific evidence, encompassing several molecular processes and interactions, including apoptosis pathway regulation, aberrant cell signaling pathways, and oncogenic genes, has not been thoroughly studied. In this direction, we attempted to project rutin-mediated oncogenic pathway regulation in various carcinomas. Additionally, we also incorporated advanced research that has uncovered the notable potential of rutin in the modulation of several key cellular functions via interaction with mRNAs, with major emphasis on elucidating direct miRNA targets of rutin as well as the process needed to transform these approaches for developing novel therapeutic interventions for the treatment of several cancers.

Vanadium-Flavonoid Complexes: A Promising Class of Molecules for Therapeutic Applications

Several reports have revealed the superior biological activity of metal ion-flavonoid complexes when compared with the parent flavonoid. Among the different metal ions explored, vanadium and its compounds are in the forefront because of their anticancer and antidiabetic properties. However, the toxicity of vanadium-based ions and their inorganic derivatives limits their therapeutic applications. Complexation of vanadium with flavonoids not only reduces its adverse effects but also augments its biological activity. This Review discusses the nature of coordination in vanadium-flavonoid complexes, their structure-activity correlations, with special emphasis on their therapeutic activities. Several investigations suggest that the superior biological activity of vanadium complexes arise because of their ability to regulate metabolic pathways distinct from those acted upon by vanadium alone. These studies serve to decipher the underlying molecular mechanism of vanadium-flavonoid complexes that can be explored further for generating a series of novel compounds with improved pharmacological and therapeutic performance.

Rutin: A Flavonoid as an Effective Sensitizer for Anticancer Therapy; Insights into Multifaceted Mechanisms and Applicability for Combination Therapy

Rutin is a unique antioxidant flavonoid that is mainly found in fruit, vegetables, cereals, and many other plant-based human diets. This review aims to highlight the in vitro anticancer properties of rutin including combination therapeutic strategies. Literature resources were gathered through PubMed, Scopus, Web of Science, and Google Scholar databases that cover the period of 1995–2021. Rutin is demonstrated to inhibit the proliferation of breast, colon, lung, and prostate cancers and other tumors. Furthermore, rutin alone or in combination with other therapeutic agents has been shown to regulate several signalling pathways involving the Ras/Raf and PI3K/Akt, MAPK, and TGF-β2/Smad2/3Akt/PTEN, etc., which are related to the processes of carcinogenesis and induction of apoptosis. The combination of rutin with other chemotherapy drugs may benefit on prevention of tumor cells by decreasing drug resistance and chemotherapy side effects. Moreover, rutin induces apoptosis synergistically with the therapeutic agent. More in vivo and clinical data are however needed to evaluate the true potential of rutin as an anticancer agent as an adjuvant. The present review highlights the effects of rutin which can be a promising candidate in combination with other antitumor drugs or alone for cancer treatment in vitro. Also, rutin can lead to decrease in drug resistance and chemotherapeutic side effects.

Ruthenium(II)-curcumin liposome nanoparticles: Synthesis, characterization, and their effects against cervical cancer

Ruthenium complexes have increased the scope for improvement in current cancer treatment by replacing platinum-based drugs. However, to reduce metal-associated toxicity, a biocompatible flavonoid, such as curcumin, is indispensable, as it offers uncompensated therapeutic benefits through formation of complexes. In this study, we synthesized metal-based flavonoid complexes using ruthenium(II) and curcumin by adopting a convenient reflux reaction, represented as Ru-Cur complexes. These complexes were thoroughly characterized using ¹H, ¹³C NMR, XPS, FT-IR, and UV-vis spectroscopy. As curcumin is sparingly soluble in water and has poor chemical stability, we loaded Ru-Cur complexes into liposomes and further formed nanoparticles (NPs) using the thin layer evaporation method. These were named Ru-Cur loaded liposome nanoparticles (RCLNPs). The effects of RCLNPs on cell proliferation was investigated using human cervical cancer cell lines (HeLa). These RCLNPs exhibited significant cytotoxicity in HeLa cells. The anticancer properties of RCLNPs were studied using reactive oxygen species (ROS), LDH, and MTT assays as well as live-dead staining. Nuclear damage studies of RCLNPs were performed in HeLa cells using the Hoechst staining assay.

The role of 3-OH in the self-assembly of pharmaceutical cocrystals of dihydroflavonol with 4,4′-bipyridine

The 3-OH group of nonplanar dihydroflavonols participates in the formation of hydrogen bonds with BPY, thereby forming cocrystals with different structures.

Evaluating the potential risk by probing the site-selective binding of rutin-Pr(III) complex to human serum albumin

Having reported that rare earth elements displayed potential toxicity in vivo, often be found in soil, plants and etc., which might be easily chelated with the natural functional molecule rutin to form rutin metal complexes, ultimately entering the human body by means of food chain. However, few reports paid the attention on the toxicology of the complexes consisting of rutin with rare earth ions. Here, we focused on the potential toxicity by probing the site-selective binding of the rutin-rare earth ions complexes to human serum albumin (HSA). As a proof-of-concept, we selected Pr³⁺ as the representative to conjugate with rutin to form rutin-Pr(III) complex, which was further applied to interact with HSA in aqueous solution. The results exhibited that the rutin-Pr(III) complex primary bound to the hydrophobic cavity at site II (subdomain IIIA) of HSA through hydrogen bonding and van der Waals force. Through the thermomechanical analysis, we found this binding process was spontaneous because of the negative ΔG. We believe that this work may offer a new insight into understanding the physiological effects (e.g. toxicology) of rutin and rare earth ions, which could be helpful to guide their rational use in the agriculture and environment-related industries.

Molecular interaction and cellular studies on combination photodynamic therapy with rutoside for melanoma A375 cancer cells: an in vitro study

Background

Melanoma as a type of skin cancer, is associated with a high mortality rate. Therefore, early diagnosis and efficient surgical treatment of this disease is very important. Photodynamic therapy (PDT) involves the activation of a photosensitizer by light at specific wavelength that interacts with oxygen and creates singlet oxygen molecules or reactive oxygen species (ROS), which can lead to tumor cell death. Furthermore, one of the main approches in the prevention and treatment of various cancers is plant compounds application. Phenolic compounds are essential class of natural antioxidants, which play crucial biological roles such as anticancer effects. It was previously suggested that flavonoid such as rutoside could acts as pro-oxidant or antioxidant. Hence, in this study, we aimed to investigate the effect of rutoside on the combination therapy with methylene blue (MB) assisted by photodynamic treatment (PDT) using red light source (660 nm; power density: 30 mW/cm²) on A375 human melanoma cancer cells.

Methods

For this purpose, the A375 human melanoma cancer cell lines were treated by MB-PDT and rutoside. Clonogenic cell survival, MTT assay, and cell death mechanisms were also determined after performing the treatment. Subsequently, after the rutoside treatment and photodynamic therapy (PDT), cell cycle and intracellular reactive oxygen species (ROS) generation were measured.

Results

The obtained results showed that, MB-PDT and rutoside had better cytotoxic and antiprolifrative effects on A375 melanoma cancer cells compared to each free drug, whereas the cytotoxic effect on HDF human dermal fibroblast cell was not significant. MB-PDT and rutoside combination induced apoptosis and cell cycle arrest in the human melanoma cancer cell line. Intracellular ROS increased in A375 cancer cell line after the treatment with MB-PDT and rutoside.

Conclusion

The results suggest that, MB-PDT and rutoside could be considered as novel approaches as the combination treatment of melanoma cancer.

The anticancer potential of the dietary polyphenol rutin: Current status, challenges, and perspectives

Rutin is one of the most common dietary polyphenols found in vegetables, fruits, and other plants. It is metabolized by the mammalian gut microbiota and absorbed from the intestines, and becomes bioavailable in the form of conjugated metabolites. Rutin exhibits a plethora of bioactive properties, making it an extremely promising phytochemical. Numerous studies demonstrate that rutin can act as a chemotherapeutic and chemopreventive agent, and its anticancer effects can be mediated through the suppression of cell proliferation, the induction of apoptosis or autophagy, and the hindering of angiogenesis and metastasis. Rutin has been found to modulate multiple molecular targets involved in carcinogenesis, such as cell cycle mediators, cellular kinases, inflammatory cytokines, transcription factors, drug transporters, and reactive oxygen species. This review summarizes the natural sources of rutin, its bioavailability, and in particular its potential use as an anticancer agent, with highlighting its anticancer mechanisms as well as molecular targets. Additionally, this review updates the anticancer potential of its analogs, nanoformulations, and metabolites, and discusses relevant safety issues. Overall, rutin is a promising natural dietary compound with promising anticancer potential and can be widely used in functional foods, dietary supplements, and pharmaceuticals for the prevention and management of cancer.