Quercetin 3,5,7,3',4'-pentamethyl ether from Kaempferia parviflora directly and effectively activates human SIRT1

A dual recognition-based strategy employing Ni-modified metal-organic framework for in situ screening of SIRT1 inhibitors from Chinese herbs

Sirtuin1 (SIRT1), an NAD+-dependent histone deacetylase, plays a crucial role in regulating molecular signaling pathways. Recently, inhibition of SIRT1 rather than its activation shows the therapeutic potential for central nervous system disorder, however, the discovered SIRT1 inhibitors remains limited. In this work, a dual recognition-based strategy was developed to screen SIRT1 inhibitors from natural resources in situ. This approach utilized a Ni-modified metal-organic framework (Ni@Tyr@UiO-66-NH2) along with cell lysate containing an engineered His-tagged SIRT1 protein, eliminating the need for purified proteins, pure compounds, and protein immobilization. The high-performance Ni@Tyr@UiO-66-NH2 was synthesized by modifying the surface of UiO-66-NH2 with Ni2+ ions to specifically capture His-tagged SIRT1 while persevering its enzyme activity. By employing dual recognition, in which Ni@Tyr@UiO-66-NH2 recognized SIRT1 and SIRT1 recognized its ligands, the process of identifying SIRT1 inhibitors from complex matrix was vastly streamlined. The developed method allowed the efficient discovery of 16 natural SIRT1 inhibitors from Chinese herbs. Among them, 6 compounds were fully characterized, and suffruticosol A was found to have an excellent IC50 value of 0.95 ± 0.12 μM. Overall, an innovative dual recognition-based strategy was proposed to efficiently identify SIRT1 inhibitors in this study, offering scientific clues for the development of drugs targeting CNS disorders.

Anticancer Activity and Molecular Mechanisms of Acetylated and Methylated Quercetin in Human Breast Cancer Cells

Quercetin, a flavonoid polyphenol found in many plants, has garnered significant attention due to its potential cancer chemoprevention. Our previous studies have shown that acetyl modification of the hydroxyl group of quercetin altered its antitumor effects in HepG2 cells. However, the antitumor effect in other cancer cells with different gene mutants remains unknown. In this study, we investigated the antitumor effect of quercetin and its methylated derivative 3,3',4',7-O-tetramethylquercetin (4Me-Q) and acetylated derivative 3,3',4',7-O-tetraacetylquercetin (4Ac-Q) on two human breast cancer cells, MCF-7 (wt-p53, caspase-3-ve) and MDA-MB-231 (mt-p53, caspase-3+ve). The results demonstrated that 4Ac-Q exhibited significant cell proliferation inhibition and apoptosis induction in both MCF-7 and MDA-MB-231 cells. Conversely, methylation of quercetin was found to lose the activity. The human apoptosis antibody array revealed that 4Ac-Q might induce apoptosis in MCF-7 cells via a p53-dependent pathway, while in MDA-MB-231 cells, it was induced via a caspase-3-dependent pathway. Furthermore, an evaluation using a superoxide inhibitor, MnTBAP, revealed 4Ac-Q-induced apoptosis in MCF-7 cells in a superoxide-independent manner. These findings provide valuable insights into the potential of acetylated quercetin as a new approach in cancer chemoprevention and offer new avenues for health product development.

Quercetin and Related Analogs as Therapeutics to Promote Tissue Repair

Quercetin is a polyphenol of the flavonoid class of secondary metabolites that is widely distributed in the plant kingdom. Quercetin has been found to exhibit potent bioactivity in the areas of wound healing, neuroprotection, and anti-aging research. Naturally found in highly glycosylated forms, aglycone quercetin has low solubility in aqueous environments, which has heavily limited its clinical applications. To improve the stability and bioavailability of quercetin, efforts have been made to chemically modify quercetin and related flavonoids so as to improve aqueous solubility while retaining bioactivity. In this review, we provide an updated overview of the biological properties of quercetin and proposed mechanisms of actions in the context of wound healing and aging. We also provide a description of recent developments in synthetic approaches to improve the solubility and stability of quercetin and related analogs for therapeutic applications. Further research in these areas is expected to enable translational applications to improve ocular wound healing and tissue repair.

The differing effects of a dual acting regulator on SIRT1

SIRT1 is an NAD+-dependent protein deacetylase that has been shown to play a significant role in many biological pathways, such as insulin secretion, tumor formation, lipid metabolism, and neurodegeneration. There is great interest in understanding the regulation of SIRT1 to better understand SIRT1-related diseases and to better design therapeutic approaches that target SIRT1. There are many known protein and small molecule activators and inhibitors of SIRT1. One well-studied SIRT1 regulator, resveratrol, has historically been regarded as a SIRT1 activator, however, recent studies have shown that it can also act as an inhibitor depending on the identity of the peptide substrate. The inhibitory nature of resveratrol has yet to be studied in detail. Understanding the mechanism behind this dual behavior is crucial for assessing the potential side effects of STAC-based therapeutics. Here, we investigate the detailed mechanism of substrate-dependent SIRT1 regulation by resveratrol. We demonstrate that resveratrol alters the substrate recognition of SIRT1 by affecting the K M values without significantly impacting the catalytic rate (k cat). Furthermore, resveratrol destabilizes SIRT1 and extends its conformation, but the conformational changes differ between the activation and inhibition scenarios. We propose that resveratrol renders SIRT1 more flexible in the activation scenario, leading to increased activity, while in the inhibition scenario, it unravels the SIRT1 structure, compromising substrate recognition. Our findings highlight the importance of substrate identity in resveratrol-mediated SIRT1 regulation and provide insights into the allosteric control of SIRT1. This knowledge can guide the development of targeted therapeutics for diseases associated with dysregulated SIRT1 activity.

New insights into Sirt1: potential therapeutic targets for the treatment of cerebral ischemic stroke

Ischemic stroke is one of the main causes of mortality and disability worldwide. However, the majority of patients are currently unable to benefit from intravenous thrombolysis or intravascular mechanical thrombectomy due to the limited treatment windows and serious complications. Silent mating type information regulation 2 homolog 1 (Sirt1), a nicotine adenine dinucleotide-dependent enzyme, has emerged as a potential therapeutic target for ischemic stroke due to its ability to maintain brain homeostasis and possess neuroprotective properties in a variety of pathological conditions for the central nervous system. Animal and clinical studies have shown that activation of Sirt1 can lessen neurological deficits and reduce the infarcted volume, offering promise for the treatment of ischemic stroke. In this review, we summarized the direct evidence and related mechanisms of Sirt1 providing neuroprotection against cerebral ischemic stroke. Firstly, we introduced the protein structure, catalytic mechanism and specific location of Sirt1 in the central nervous system. Secondly, we list the activators and inhibitors of Sirt1, which are primarily divided into three categories: natural, synthetic and physiological. Finally, we reviewed the neuroprotective effects of Sirt1 in ischemic stroke and discussed the specific mechanisms, including reducing neurological deficits by inhibiting various programmed cell death such as pyroptosis, necroptosis, ferroptosis, and cuproptosis in the acute phase, as well as enhancing neurological repair by promoting angiogenesis and neurogenesis in the later stage. Our review aims to contribute to a deeper understanding of the critical role of Sirt1 in cerebral ischemic stroke and to offer novel therapeutic strategies for this condition.

Enzymatically modified isoquercitrin in soy protein temporarily enhanced the plasma amino-acid concentrations, antioxidant index, and plasma hormone levels: a randomized, double-blind cross-over trial

This study investigated the effects of a dietary protein supplement containing enzymatically modified isoquercitrin (EMIQ) on plasma amino-acid levels in healthy people. A randomized double-blind cross-over trial (UMIN000044791) was conducted with a sample of nine healthy individuals. These participants ingested soy protein with or without 42 mg EMIQ for 7 days after performing mild exercise. Plasma amino-acid levels were measured before ingestion and at 15, 30, 45, 60, 90, 120, 180, and 240 min after ingestion on the last day. The concentrations of total amino acids at 0 and 120 min and easily oxidized amino acids at 120 min were significantly higher in the plasma of individuals who consumed 42 mg EMIQ. Oxidative stress levels were lower and plasma testosterone levels were higher in participants who ingested soy protein with 42 mg EMIQ than in those who did not. These results suggest that daily ingestion of soy protein with 42 mg EMIQ can be useful for effective protein absorption.

The industrially important genus Kaempferia: An ethnopharmacological review

Kaempferia, a genus of the family Zingiberaceae, is widely distributed with more than 50 species which are mostly found throughout Southeast Asia. These plants have important ethnobotanical significance as many species are used in Ayurvedic and other traditional medicine preparations. This genus has received a lot of scholarly attention recently as a result of the numerous health advantages it possesses. In this review, we have compiled the scientific information regarding the relevance, distribution, industrial applications, phytochemistry, ethnopharmacology, tissue culture and conservation initiative of the Kaempferia genus along with the commercial realities and limitations of the research as well as missing industrial linkages followed by an exploration of some of the likely future promising clinical potential. The current review provides a richer and deeper understanding of Kaempferia, which can be applied in areas like phytopharmacology, molecular research, and industrial biology. The knowledge from this study can be further implemented for the establishment of new conservation strategies.

Quercetin Decreases Corneal Haze In Vivo and Influences Gene Expression of TGF-Beta Mediators In Vitro

We have previously reported the flavonoid, quercetin, as a metabolic regulator and inhibitor of myofibroblast differentiation in vitro. Our current study evaluated the effects of topical application of quercetin on corneal scar development using two different animal models followed by RNA analysis in vitro. Wild-type C57BL/6J mice were anesthetized and the corneal epithelium and stroma were manually debrided, followed by quercetin (0.5, 1, 5, or 50 mM) or vehicle application. Corneal scarring was assessed for 3 weeks by slit lamp imaging and clinically scored. In a separate animal study, six New Zealand White rabbits underwent lamellar keratectomy surgery, followed by treatment with 5 mM quercetin or vehicle twice daily for three days. Stromal backscattering was assessed at week 3 by in vivo confocal microscopy. In mice, a single dose of 5 mM quercetin reduced corneal scar formation. In rabbits, stromal backscattering was substantially lower in two out of three animals in the quercetin-treated group. In vitro studies of human corneal fibroblasts showed that quercetin modulated select factors of the transforming growth factor-β (TGF-β) signaling pathway. These results provide evidence that quercetin may inhibit corneal scarring. Further studies in a larger cohort are required to validate the efficacy and safety of quercetin for clinical applications.

Screening of flavor compounds using Ucp1-luciferase reporter beige adipocytes identified 5-methylquinoxaline as a novel UCP1-inducing compound

Uncoupling protein 1 (UCP1) in brown or beige adipocytes is a mitochondrial protein that is expected to enhance whole-body energy expenditure. For the high-throughput screening of UCP1 transcriptional activity regulator, we established a murine inguinal white adipose tissue-derived Ucp1-luciferase reporter preadipocyte line. Using this reporter preadipocyte line, 654 flavor compounds were screened, and a novel Ucp1 expression-inducing compound, 5-methylquinoxaline, was identified. Adipocytes treated with 5-methylquinoxaline showed increased Ucp1 mRNA expression levels and enhanced oxygen consumption. 5-Methylquinoxaline induced Ucp1 expression through peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), and 5-methylquinoxaline-induced PGC1α activation seemed to be partially regulated by its phosphorylation or deacetylation. Thus, our Ucp1-luciferase reporter preadipocyte line is a useful tool for screening of Ucp1 inductive compounds.

Anti-Oxidative, Anti-Inflammatory and Anti-Apoptotic Effects of Flavonols: Targeting Nrf2, NF-κB and p53 Pathways in Neurodegeneration

Neurodegenerative diseases are one of the leading causes of disability and death worldwide. Intracellular transduction pathways that end in the activation of specific transcription factors are highly implicated in the onset and progression of pathological changes related to neurodegeneration, of which those related to oxidative stress (OS) and neuroinflammation are particularly important. Here, we provide a brief overview of the key concepts related to OS- and neuroinflammation-mediated neuropathological changes in neurodegeneration, together with the role of transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB). This review is focused on the transcription factor p53 that coordinates the cellular response to diverse genotoxic stimuli, determining neuronal death or survival. As current pharmacological options in the treatment of neurodegenerative disease are only symptomatic, many research efforts are aimed at uncovering efficient disease-modifying agents. Natural polyphenolic compounds demonstrate powerful anti-oxidative, anti-inflammatory and anti-apoptotic effects, partially acting as modulators of signaling pathways. Herein, we review the current understanding of the therapeutic potential and limitations of flavonols in neuroprotection, with emphasis on their anti-oxidative, anti-inflammatory and anti-apoptotic effects along the Nrf2, NF-κB and p53 pathways. A better understanding of cellular and molecular mechanisms of their action may pave the way toward new treatments.