Synthesis and biological evaluation of quercetin and resveratrol peptidyl derivatives as potential anticancer and antioxidant agents

Synthesis, biological evaluation and docking studies of N-substituted resveratrol derivatives

A total of 19 resveratrol derivatives, including 12 imines and 7 amines, were synthesized, among which compounds 1, 5, 6, 7', 11', and 13 are new compounds. The anti-inflammatory and antitumor activities of these compounds were evaluated in vitro. The results revealed that compounds 1, 6, 8', 12, and 12' exhibited significant inhibitory effects (> 50%) on NO production at the concentration of 10 μM and their NO production inhibitory activities have a significant concentration-dependent ability. Additionally, compounds 8' and 12' showed promising COX-2 inhibitory activity, and the molecular docking analysis indicated their stable binding to multiple amino acid residues within the active pocket of COX-2 through hydrogen bonding. Moreover, compound 12' exhibited inhibitory effects on various tumor cell lines and induced apoptosis in MCF-7 breast cancer cells, which was not observed with resveratrol alone. Therefore, the N-substituted structural modification of resveratrol would have possibly enhanced the bioactivity of resveratrol and facilitated its application.

Effects of Simulated Gastrointestinal Conditions on Combined Potentially Probiotic Limosilactobacillus fermentum 296, Quercetin, and/or Resveratrol as Bioactive Components of Novel Nutraceuticals

This study evaluated the effects of simulated gastrointestinal conditions (SGIC) on combined potentially probiotic Limosilactobacillus fermentum 296 (~ 10 log CFU/mL), quercetin (QUE, 160 mg), and/or resveratrol (RES, 150 mg) as the bioactive components of novel nutraceuticals. Four different nutraceuticals were evaluated during exposure to SGIC and analyzed the plate counts and physiological status of L. fermentum 296, contents and bioaccessibility of QUE and RES, and antioxidant capacity. Nutraceuticals with QUE and RES had the highest plate counts (4.94 ± 0.32 log CFU/mL) and sizes of live cell subpopulations (28.40 ± 0.28%) of L. fermentum 296 after SGIC exposure. An index of injured cells (Gmean index, arbitrary unit defined as above 0.5) indicated that part of L. fermentum 296 cells could be entered the viable but nonculturable state when the nutraceuticals were exposed to gastric and intestinal conditions while maintaining vitality. The nutraceuticals maintained high contents (QUE ~ 29.17 ± 0.62 and RES ~ 23.05 mg/100 g) and bioaccessibility (QUE ~ 41.0 ± 0.09% and RES ~ 67.4 ± 0.17%) of QUE and RES, as well as high antioxidant capacity (ABTS assay ~ 88.18 ± 1.16% and DPPH assay 75.54 ± 0.65%) during SGIC exposure, which could be linked to the protective effects on L. fermentum 296 cells. The developed nutraceuticals could cross along the gastrointestinal tract with high concentrations of functioning potentially probiotic cells and bioavailable phenolic compounds to exert their beneficial impacts on consumer health, being an innovative strategy for the co-ingestion of these bioactive components.

Discovery of bletillain, an unusual benzyl polymer with significant autophagy-inducing effects in A549 lung cancer cells through the Akt/GSK-3β/β-catenin signaling pathway

Lung cancer is one of the most malignant tumors with the highest mortality and morbidity. The tubers of Bletilla striata are known as "an excellent medicine for lung diseases" in traditional Chinese medicine. This study performed a targeted study to explore compounds with anti-lung cancer activity and the molecular mechanisms using A549 cells. Eighteen bibenzyl derivatives, including four new compounds (13, 14, 16, and 18), were isolated from the tubers of B. striata. Analysis of the structure-activity relationship indicated that the cytotoxicity of the bibenzyls against A549 cells increased gradually as the number of the benzyl groups in the structures increased. Bletillain (18), an unusual benzyl polymer, was found to be the most active compound. Further flow cytometric analysis, dual-luciferase assays, real-time PCR assays, and western blot assays revealed that bletillain induced autophagy in A549 cells by regulating the Akt/GSK-3β/β-catenin signaling pathway. Beclin 1, LC3, and p62 are downstream autophagy factors of Akt, and Beclin 1 was the key autophagy factor. These results suggested that bibenzyls of B. striata play important roles in the treatment of lung cancer and provided scientific evidence illustrating why the tubers of B. striata are a suitable medicine for the treatment of lung cancer in traditional Chinese medicine.

Modulation of Long Non-Coding RNAs by Different Classes of Secondary Metabolites from Plants: A Mini-Review on Antitumor Effects

The broad pharmacological spectrum of plants is related to their secondary metabolism, which is responsible for the synthesis of different compounds that have multiple effects on cellular physiology. Among the biological effects presented by phytochemicals, their use for the prevention and treatment of cancer can be highlighted. This occurs due to several mechanisms of antitumor action demonstrated by these compounds, including regulation of the cell signaling pathways and inhibition of tumor growth. In this way, long non-coding RNAs (lncRNAs) appear to be promising targets for the treatment of cancer. Their deregulation has already been related to a variety of clinical-pathological parameters. However, the effects of secondary metabolites on lncRNAs are still restricted. For this reason, the present review aimed to gather data on phytochemicals with action on lncRNAs in order to confirm their possible antitumor potential. According to the literature, terpenoid and flavonoid are the main examples of secondary metabolites involved with lncRNAs activity. In addition, the lncRNAs H19, CASC2, HOTAIR, NKILA, CCAT1, MALAT1, AFAP1-AS1, MEG3, and CDKN2B-AS1 can be highlighted as important targets in the search for new anti-tumor agents since they act as modulating pathways related to cell proliferation, cell cycle, apoptosis, cell migration and invasion. Finally, challenges for the use of natural products as a commercial drug were also discussed. The low yield, selectivity index and undesirable pharmacokinetic parameters were emphasized as a difficulty for obtaining these compounds on a large scale and for improving the potency of its biological effect. However, the synthesis and/or development of formulations were suggested as a possible approach to solve these problems. All of these data together confirm the potential of secondary metabolites as a source of new anti-tumor agents acting on lncRNAs.

Potential Mechanisms of Plant-Derived Natural Products in the Treatment of Cervical Cancer

Cervical cancer is the second most common gynecological malignancy globally; it seriously endangers women’s health because of its high morbidity and mortality. Conventional treatments are prone to drug resistance, recurrence and metastasis. Therefore, there is an urgent need to develop new drugs with high efficacy and low side effects to prevent and treat cervical cancer. In recent years, plant-derived natural products have been evaluated as potential anticancer drugs that preferentially kill tumor cells without severe adverse effects. A growing number of studies have shown that natural products can achieve practical anti-cervical-cancer effects through multiple mechanisms, including inhibition of tumor-cell proliferation, induction of apoptosis, suppression of angiogenesis and telomerase activity, enhancement of immunity and reversal of multidrug resistance. This paper reviews the therapeutic effects and mechanisms of plant-derived natural products on cervical cancer and provides references for developing anti-cervical-cancer drugs with high efficacy and low side effects.

Combination of natural antivirals and potent immune invigorators: A natural remedy to combat COVID-19

The flare‐up in severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) that emerged in December 2019 in Wuhan, China, and spread expeditiously worldwide has become a health challenge globally. The rapid transmission, absence of anti‐SARS‐CoV‐2 drugs, and inexistence of vaccine are further exacerbating the situation. Several drugs, including chloroquine, remdesivir, and favipiravir, are presently undergoing clinical investigation to further scrutinize their effectiveness and validity in the management of COVID‐19. Natural products (NPs) in general, and plants constituents specifically, are unique sources for various effective and novel drugs. Immunostimulants, including vitamins, iron, zinc, chrysin, caffeic acid, and gallic acid, act as potent weapons against COVID‐19 by reinvigorating the defensive mechanisms of the immune system. Immunity boosters prevent COVID‐19 by stimulating the proliferation of T‐cells, B‐cells, and neutrophils, neutralizing the free radicals, inhibiting the immunosuppressive agents, and promoting cytokine production. Presently, antiviral therapy includes several lead compounds, such as baicalin, glycyrrhizin, theaflavin, and herbacetin, all of which seem to act against SARS‐CoV‐2 via particular targets, such as blocking virus entry, attachment to host cell receptor, inhibiting viral replication, and assembly and release.

Current methodologies to refine bioavailability, delivery, and therapeutic efficacy of plant flavonoids in cancer treatment

Over the last two decades, several advancements have been made to improve the therapeutic efficacy of plant flavonoids, especially in cancer treatment. Factors such as low bioavailability, poor flavonoid stability and solubility, ineffective targeted delivery, and chemo-resistance hinder the application of flavonoids in anti-cancer therapy. Many anti-cancer compounds failed in the clinical trials because of unexpected altered clearance of flavonoids, poor absorption after administration, low efficacy, and/or adverse effects. Hence, the current research strategies are focused on improving the therapeutic efficacy of plant flavonoids, especially by enhancing their bioavailability through combination therapy, engineering gut microbiota, regulating flavonoids interaction with adenosine triphosphate binding cassette efflux transporters, and efficient delivery using nanocrystal and encapsulation technologies. This review aims to discuss different methodologies with examples from reported dietary flavonoids that showed an enhanced anti-cancer efficacy in both in vitro and in vivo models. Further, the review discusses the recent progress in biochemical modifications of flavonoids to improve bioavailability, solubility, and therapeutic efficacy.

Novel nano-pomegranates based on astragalus polysaccharides for targeting ERα-positive breast cancer and multidrug resistance

Chemotherapy is an important method for treating breast cancer. However, multidrug resistance is one of the major challenges in breast cancer chemotherapy. There is an urgent need to develop novel, effective antitumor strategies that will perfect existing therapeutic regimens. In this study, the double-targeted nanocarrier, Quercetin-3'3-dithiodipropionic acid-Astragalus polysaccharides-Folic acid (QDAF), was successfully synthesized and self-assembled into a neoteric nano-targeted delivery strategy, named nano-pomegranates, and which were utilized to effectively inhibit multidrug resistance in estrogen receptor α (ERα)-positive breast tumor. The outstanding abilities of nano-pomegranates to release the drug in a reducing environment was determined by in vitro release assay. The cellular studies in MCF-7 cells were examined that nano-pomegranates have remarkable efficiencies of enhancing cellular uptake, inhibition and necrosis and apoptosis. In vivo antitumor experiments showed that nano-pomegranates have better anti-tumor effects and lower systemic toxicity than free Cur. In conclusion, nano-pomegranates have great potential in anti-breast cancer treatment.

Design and synthesis of novel antimicrobial peptide scaffolds

Muramic acid (Mur), a sugar amino acid (SAA), is present in the cell walls of bacteria asN-acetyl muramic acid (MurNAc) where together with ofN-acetylglucosamine (GlcNAc) and peptide makes main building block of peptidoglycan (PGN). It was challenging to incorporate muramic acid as SAA characteristic for bacteria into the peptides and investigate the antimicrobial activity of these scaffolds. Four building units were used in designing the desired peptide: muramic acid, tetrapeptide Leu-Ser-Lys-Leu, N^ε-Lys, and Asn. Positions of three components were changeable while the position of Asn was always C-terminal (in linear peptides). The glycopeptide libraries of linear and cyclic peptides were synthesized using solid-phase peptide synthesis (SPPS). The antimicrobial effect of linear and cyclic glycopeptides, as well as the LSKL sequence used as a control, was investigated on several standard laboratory microbial strains. Liner glycopeptide with sequences Leu-Ser-Lys-Leu-N^ε-Lys-Mur-Asn was active onStaphylococcus aureus(Gram-positive bacteria). Prepared compounds did not show activity towards applied tumor and normal human cell lines.

Resveratrol - A comprehensive review of recent advances in anticancer drug design and development

Resveratrol is a natural polyphenolic stilbene isolated from various plants, foods and beverages with a broad spectrum of biological and pharmacological properties through modulating diverse targets and signaling pathways. Particularly, it has attracted a great deal of attention as a promising and multitarget anticancer agent due to its potential use in chemoprevention and chemotherapy of various tumors. However, unfavorable pharmacokinetics/pharmacodynamics profile such as poor bioavailability restricted its applications. Therefore, medicinal chemists have synthesized a lot of novel derivatives and analogues of resveratrol using different modification strategies to overcome these limitations and improve anticancer efficacy. Herein, we reviewed the design, synthesis, structure-activity relationship and mechanism of the most potent and privileged resveratrol-based compounds that showed promising anticancer activities in the last five years. We classified these compounds into the ten different categories based on their chemical structure similarities.

Synthesis and biological evaluation of resveratrol derivatives with anti-breast cancer activity

Resveratrol is a natural phytoestrogen produced by plants to protect themselves from injury, UV irradiation, and fungal attack. The main active structure is E-resveratrol, which has many pharmacological activities. As the structure of resveratrol is similar to the natural estrogen 17β-estradiol and the synthetic estrogen E-diethylstilbestrol, resveratrol is used in reducing the incidence of breast cancer. However, the therapeutic application of resveratrol is limited due to its low bioavailability. To improve its bioavailability and pharmacological activity, some resveratrol derivatives have been designed and synthesized by substitutions of methoxy, hydroxyl, and other functional groups or heterocyclic esterification either on the "A" or "B" ring, and double bonds were replaced by imine bonds and isometric heterocycles such as naphthyl and imidazole, or synthetic resveratrol oligomers. The structures, synthetic routes, and evaluation of the biological activities of these compounds are discussed. These are aimed at providing some references for the study of resveratrol derivatives in anti-breast cancer treatment.