Synthesis of chalcone incorporated quinazoline derivatives as anticancer agents

Design, In Silico Molecular Docking, and ADMET Prediction of Amide Derivatives of Chalcone Nucleus as EGFR Inhibitors for the Treatment of Cancer

BACKGROUND

Cancer is a devastating disease. Many studies have shown that the primary causes of the aggressive and resistant types of cancer are the overexpression of receptors and growth factors, activation of oncogenes, and the inactivation of tumour suppressor genes. One such receptor is the epidermal growth factor receptor (EGFR), which is used as a drug target for the treatment of cancer.

OBJECTIVE

This study aimed to develop the new chemical entities of amide derivatives of chalcone as EGFR inhibitors using structure-activity relationship (SAR) studies, molecular docking, and ADMET (absorption, distribution, metabolism, excretion, and toxicity) studies.

METHOD

New chemical entities (NCE) were designed based on literature findings. The Schrodinger 13.4 software was used for the molecular docking study. While Quickprop and Pro Tox-II online tools were used for ADME and toxicity prediction, respectively. .

RESULT

In this work, all compounds were subjected to an in-silico ADMET analysis. After pharmacokinetic and toxicity profile predictions, the molecules were further analysed by molecular docking. As a result of molecular docking, molecules AC9 and AC19 showed comparable docking scores compared to standard Afatinib.

CONCLUSION

Molecules AC9 and AC19 showed good docking scores and a promising ADMET profile. In the future, these derivatives can be further evaluated for wet lab studies and determination of their biological activity.

Molecular dynamics simulation approach of hybrid chalcone-thiazole complex derivatives for DNA gyrase B inhibition: lead generation

Compounds bearing thiazole and chalcone groups have been reported to be excellent leads for antibacterial, antitubercular and anticancer activities. In view of this, we performed quantitative structure-activity relationship studies using QSARINS for dataset preparation and for developing validated QSAR models that can predict novel series of thiazole-chalcone hybrids and further evaluate them for bioactivities. The molecular descriptors AATS8i, AVP-1, MoRSEE17 and GATSe7 were found to be active in predicting the structure-activity relationship. Molecular docking and dynamics simulation studies of the developed leads have shown insights into structural analysis. Furthermore, computational studies using AutoDock and Desmond predicted the key binding interactions responsible for the activity and the SwissADME tool computed the in silico drug likeliness properties. The lead compound 178 generated through this study creates a route for the optimization and development of novel drugs against tuberculosis infections. RMSD, RMSF, RoG, H-bond and SASA analysis confirmed the stable binding of compound 178 with the 6J90 structure. In addition, MM-PBSA and MM-GBSA also confirm the docking results. We propose the designed compound 178 as the best theoretical lead, which may further be experimentally studied for selective inhibition.

Design, synthesis, and modelling study of new 1,2,3-triazole/chalcone hybrids with antiproliferative action as epidermal growth factor receptor inhibitors

A novel series of 1,2,3-triazole/chalcone hybrids 6a-n was designed and synthesized using a molecular hybridization approach to develop a new cytotoxic agent capable of targeting epidermal growth factor receptor (EGFR) and/or BRAF. The antiproliferative effect of the novel hybrids was investigated against four cancer cells using doxorubicin as a reference. Hybrids 6a, 6d, 6f-h, and 6n have the highest antiproliferative activity (IC₅₀ values 0.95-1.80 μM) compared to doxorubicin (IC₅₀ 1.14 μM). The most potent antiproliferative derivative, compound 6d, was also the most potent EGFR inhibitor with an IC₅₀ of 0.09 ± 0.05 μM, which is comparable to the reference Erlotinib (IC₅₀  = 0.05 ± 0.03 μM). 6d has modest BRAF inhibitory action with an IC₅₀ of 0.90 ± 0.10 μM. The findings were also related to molecular docking studies, which provided models of strong interactions with the EGFR-TK domain for the inhibitors. In cell cycle analysis, hybrid 6d caused a cell cycle arrest at the G1 transition phase.

Chalcone: A Promising Bioactive Scaffold in Medicinal Chemistry

Chalcones are a class of privileged scaffolds with high medicinal significance due to the presence of an α,β-unsaturated ketone functionality. Numerous functional modifications of chalcones have been reported, along with their pharmacological behavior. The present review aims to summarize the structures from natural sources, synthesis methods, biological characteristics against infectious and non-infectious diseases, and uses of chalcones over the past decade, and their structure–activity relationship studies are detailed in depth. This critical review provides guidelines for the future design and synthesis of various chalcones. In addition, this could be highly supportive for medicinal chemists to develop more promising candidates for various infectious and non-infectious diseases.

Two Important Anticancer Mechanisms of Natural and Synthetic Chalcones

ATP-binding cassette subfamily G and tubulin pharmacological mechanisms decrease the effectiveness of anticancer drugs by modulating drug absorption and by creating tubulin assembly through polymerization. A series of natural and synthetic chalcones have been reported to have very good anticancer activity, with a half-maximal inhibitory concentration lower than 1 µM. By modulation, it is observed in case of the first mechanism that methoxy substituents on the aromatic cycle of acetophenone residue and substitution of phenyl nucleus by a heterocycle and by methoxy or hydroxyl groups have a positive impact. To inhibit tubulin, compounds bind to colchicine binding site. Presence of methoxy groups, amino groups or heterocyclic substituents increase activity.

Synthesis of Chalcones Derivatives and Their Biological Activities: A Review

Chalcone derivatives are considered valuable species because they possess a ketoethylenic moiety, CO-CH=CH-. Due to the presence of a reactive α,β-unsaturated carbonyl group, chalcones and their derivatives possess a wide spectrum of antiproliferative, antifungal, antibacterial, antiviral, antileishmanial, and antimalarial pharmacological properties. Recent developments in heterocyclic chemistry have led to the synthesis of chalcone derivatives, which had been biologically investigated toward certain disease targets. The major aspect of this review is to present the most recent synthesis of chalcones bearing N, O, and/or S heterocycles, revealing their biological potential during the past decade (2010-2021). Based on a review of the literature, many chalcone-heterocycle hybrids appear to exhibit promise as future drug candidates owing to their similar or superior activities compared to those of the standards. Thus, this review may prove to be beneficial for the development and design of new potent therapeutic drugs based on previously developed strategies.

Identification of novel furo[2,3-d]pyrimidine based chalcones as potent anti-breast cancer agents: synthesis, in vitro and in vivo biological evaluation

Various substituted synthetic chalcones demonstrated potent anti-cancer activities. In the current study a series of novel furo[2,3-d]pyrimidine based chalcones were synthesized as potential anticancer agents. Among the different substituted derivatives, two of the halogen bearing chalcones, 5d and 5e, demonstrated potent anti-proliferative activity against an NCI 59 cell line, with mean GI50 values of 2.41 μM and 1.23 μM, respectively. Moreover, both compounds showed pronounced cytotoxic activity (5d; 1.20 ± 0.21, 5e; 1.90 ± 0.32) against the resistant MCF-7 cell line when compared to doxorubicin; 3.30 ± 0.18. Such outcomes provoked the initiation of an in vivo anticancer assessment study, where compound 5e revealed comparable results to doxorubicin.

MSCs as Tumor-Specific Vectors for the Delivery of Anticancer Agents-A Potential Therapeutic Strategy in Cancer Diseases: Perspectives for Quinazoline Derivatives

Mesenchymal stem cells (MSCs) are considered to be a powerful tool in the treatment of various diseases. Scientists are particularly interested in the possibility of using MSCs in cancer therapy. The research carried out so far has shown that MSCs possess both potential pro-oncogenic and anti-oncogenic properties. It has been confirmed that MSCs can regulate tumor cell growth through a paracrine mechanism, and molecules secreted by MSCs can promote or block a variety of signaling pathways. These findings may be crucial in the development of new MSC-based cell therapeutic strategies. The abilities of MSCs such as tumor tropism, deep migration and immune evasion have evoked considerable interest in their use as tumor-specific vectors for small-molecule anticancer agents. Studies have shown that MSCs can be successfully loaded with chemotherapeutic drugs such as gemcitabine and paclitaxel, and can release them at the site of primary and metastatic neoplasms. The inhibitory effect of MSCs loaded with anti-cancer agents on the proliferation of cancer cells has also been observed. However, not all known chemotherapeutic agents can be used in this approach, mainly due to their cytotoxicity towards MSCs and insufficient loading and release capacity. Quinazoline derivatives appear to be an attractive choice for this therapeutic solution due to their biological and pharmacological properties. There are several quinazolines that have been approved for clinical use as anticancer drugs by the US Food and Drug Administration (FDA). It gives hope that the synthesis of new quinazoline derivatives and the development of methods of their application may contribute to the establishment of highly effective therapies for oncological patients. However, a deeper understanding of interactions between MSCs and tumor cells, and the exploration of the possibilities of using quinazoline derivatives in MSC-based therapy is necessary to achieve this goal. The aim of this review is to discuss the prospects for using MSC-based cell therapy in cancer treatment and the potential use of quinazolines in this procedure.

Quinazoline analogues as cytotoxic agents; QSAR, docking, and in silico studies

Background and purpose:

Synthesis and investigation of pharmacological activity of novel compounds are time and money-consuming. However, computational techniques, docking, and in silico studies have facilitated drug discovery research to design pharmacologically effective compounds.

Experimental approach:

In this study, a series of quinazoline derivatives were applied to quantitative structure-activity relationship (QSAR) analysis. A collection of chemometric methods were conducted to provide relations between structural features and cytotoxic activity of a variety of quinazoline derivatives against breast cancer cell line. An in silico-screening was accomplished and new impressive lead compounds were designed to target the epidermal growth factor receptor (EGFR)-active site based on a new structural pattern. Molecular docking was performed to delve into the interactions, free binding energy, and molecular binding mode of the compounds against the EGFR target.

Findings/Results:

A comparison between different methods significantly indicated that genetic algorithm-partial least-squares were selected as the best model for quinazoline derivatives. In the current study, constitutional, functional, chemical, resource description framework, 2D autocorrelation, and charge descriptors were considered as significant parameters for the prediction of anticancer activity of quinazoline derivatives. In silico screening was employed to discover new compounds with good potential as anticancer agents and suggested to be synthesized. Also, the binding energy of docking simulation showed desired correlation with QSAR and experimental data.

Conclusion and implications:

The results showed good accordance between binding energy and QSAR results. Compounds Q₁-Q₃₀ are desired to be synthesized and applied to in vitro evaluation.

A Review: Discovering 1,3,4-oxadiazole and chalcone nucleus for cytotoxicity/EGFR inhibitory anticancer activity

INTRODUCTION

Cancer is reported to be one of the most life-threatening diseases. Major limitations of currently used anticancer agents are drug resistance, very small therapeutic index, and severe, multiple side effects.

OBJECTIVE

The current scenario necessitates developing new anticancer agents, acting on novel targets for effectively controlling cancer. The epidermal growth factor receptor is one such target, which is being explored for 1,3,4-oxadiazole and chalcone nuclei.

METHOD

Findings of different researchers working on these scaffolds have been reviewed and analyzed, and the outcomes were summarized. This review focuses on Structure-Activity Relationship studies (SARs) and computational studies of various 1,3,4-oxadiazole and chalcone hybrids/derivatives reported as cytotoxic/EGFR-TK inhibitory anticancer activity.

RESULT AND CONCLUSION

1,3,4-oxadiazole and chalcone hybrids/derivatives with varied substitutions are found to be effective pharmacophores in obtaining potent anticancer activity. Having done a thorough literature survey, we conclude that this review will surely provide firm and better insights to the researchers to design and develop potent hybrids/derivatives that inhibit EGFR.

The Quinazoline-Chalcone and Quinazolinone-Chalcone Hybrids: A Promising Combination for Biological Activity

Quinazoline and/or chalcones derivatives are important targets in several areas of chemical sciences, mainly, in the medicinal chemistry and pharmaceutical research. The purpose of this review was to systematize the information available in the literature, including patents, regarding the benefits, exerted by the combination of these two pharmacophores into single molecules. These hybrid compounds can exhibit different biological activities, causing a synergistic or a new effect, compared to the individuals. The variability of biological activities includes anticancer, anti-Alzheimer, antiviral and antimicrobial activities, among others. Additionally, synthetic methodologies to prepare the different molecular architectures were discussed based on their similarities. The increasing number of publications indicates the importance of molecular hybridization in the field of drug discovery.

Pyrimidine: a review on anticancer activity with key emphasis on SAR

Background

Cancer is a global health challenge, it impacts the quality of life and its treatment is associated with several side effects. Resistance of the cancer cells to the existing drugs has led to search for novel anticancer agents. Pyrimidine, a privileged scaffold, is part of living organisms and plays vital role in various biological procedures as well as in cancer pathogenesis. Due to resemblance in structure with the nucleotide base pair of DNA and RNA, it is recognized as valuable compound in the treatment of cancer.

Main text

Many novel pyrimidine derivatives have been designed and developed for their anticancer activity in the last few years. The present review aims to focus on the structure activity relationship (SAR) of pyrimidine derivatives as anticancer agent from the last decade.

Conclusion

This review intends to assist in the development of more potent and efficacious anticancer drugs with pyrimidine scaffold.

Graphical abstract

Thiazole Ring-A Biologically Active Scaffold

BACKGROUND

Thiazole is a good pharmacophore nucleus due to its various pharmaceutical applications. Its derivatives have a wide range of biological activities such as antioxidant, analgesic, and antimicrobial including antibacterial, antifungal, antimalarial, anticancer, antiallergic, antihypertensive, anti-inflammatory, and antipsychotic. Indeed, the thiazole scaffold is contained in more than 18 FDA-approved drugs as well as in numerous experimental drugs.

OBJECTIVE

To summarize recent literature on the biological activities of thiazole ring-containing compounds Methods: A literature survey regarding the topics from the year 2015 up to now was carried out. Older publications were not included, since they were previously analyzed in available peer reviews.

RESULTS

Nearly 124 research articles were found, critically analyzed, and arranged regarding the synthesis and biological activities of thiazoles derivatives in the last 5 years.

Thiazole-Chalcone Hybrids as Prospective Antitubercular and Antiproliferative Agents: Design, Synthesis, Biological, Molecular Docking Studies and In Silico ADME Evaluation

Compounds bearing thiazole and chalcone pharmacophores have been reported to possess excellent antitubercular and anticancer activities. In view of this, we designed, synthesized and characterized a novel series of thiazole-chalcone hybrids (1-20) and further evaluated them for antitubercular and antiproliferative activities by employing standard protocols. Among the twenty compounds, chalcones 12 and 7, containing 2,4-difluorophenyl and 2,4-dichlorophenyl groups, showed potential antitubercular activity higher than the standard pyrazinamide (MIC = 25.34 µM) with MICs of 2.43 and 4.41 µM, respectively. Chalcone 20 containing heteroaryl 2-thiazolyl moiety exhibited promising antiproliferative activity against the prostate cancer cell line (DU-145), higher than the standard methotrexate (IC50 = 11 ± 1 µM) with an IC50 value of 6.86 ± 1 µM. Furthermore, cytotoxicity studies of these compounds against normal human liver cell lines (L02) revealed that the target molecules were comparatively less selective against L02. Additional computational studies using AutoDock predicted the key binding interactions responsible for the activity and the SwissADME tool computed the in silico drug likeliness properties. The lead compounds generated through this study, create a way for the optimization and development of novel drugs against tuberculosis infections and prostate cancer.

Phytochemical composition and health properties of Sembung plant (Blumea balsamifera): A review

Indonesia's mindset has been focusing on the use of natural medicines, food, and healing practices widely recognized by the nation's culture. Traditional medicines and herbs used in traditional medicine can often lead to the discovery of drugs against certain diseases. The aim of this review was to study evidence-based data on the importance of Sembung plant, Blumea balsamifera, as a potential traditional medicine. The distribution, ethnopharmacology, secondary metabolites, and bioactivity against several diseases are focused in this review. Information and research related to Sembung plant were searched using the terms "B. balsamifera," "phytochemicals," and "pharmacological activity" on ResearchGate, Google Scholar, Science Direct, PubMed, and scientific information-based databases up to 2020. Several ethnomedical articles recommend B. balsamifera for the treatment of sinusitis, colic pain, cough, kidney stones, flu, or as a diuretic. This knowledge has already been applied in several countries in Southeast Asia. B. balsamifera has been reported to contain several phytochemicals both volatile (terpenoids, fatty acids, phenols, alcohol, aldehydes, ethers, ketones, pyridines, furans, and alkanes) and non-volatile (flavonoids, flavanones, and chalcones). Extracts and phytochemicals of B. balsamifera contain several biological capacities such as antioxidant, antimicrobial, antifungal, anti-inflammatory, hypolipidemic, anti-infertility, hepatoprotective activity, antidiabetic, gastroprotective, antitumor, anticancer, and immunomodulatory agent against Coronavirus disease-19 infection. This review provides essential data for the potential application of B. balsamifera as a nutraceutical or in future medicinal preparations.

Discovery of novel JAK2 and EGFR inhibitors from a series of thiazole-based chalcone derivatives

The Janus kinase (JAK) and epidermal growth factor receptor (EGFR) have been considered as potential targets for cancer therapy due to their role in regulating proliferation and survival of cancer cells. In the present study, the aromatic alkyl-amino analogs of thiazole-based chalcone were selected to experimentally and theoretically investigate their inhibitory activity against JAK2 and EGFR proteins as well as their anti-cancer effects on human cancer cell lines expressing JAK2 (TF1 and HEL) and EGFR (A549 and A431). In vitro cytotoxicity screening results demonstrated that the HEL erythroleukemia cell line was susceptible to compounds 11 and 12, whereas the A431 lung cancer cell line was vulnerable to compound 25. However, TF1 and A549 cells were not sensitive to our thiazole derivatives. From kinase inhibition assay results, compound 25 was found to be a dual inhibitor against JAK2 and EGFR, whereas compounds 11 and 12 selectively inhibited the JAK2 protein. According to the molecular docking analysis, compounds 11, 12 and 25 formed hydrogen bonds with the hinge region residues Lys857, Leu932 and Glu930 and hydrophobically came into contact with Leu983 at the catalytic site of JAK2, while compound 25 formed a hydrogen bond with Met769 at the hinge region, Lys721 near a glycine loop, and Asp831 at the activation loop of EGFR. Altogether, these potent thiazole derivatives, following Lipinski's rule of five, could likely be developed as a promising JAK2/EGFR targeted drug(s) for cancer therapy.

Evaluation of antitumor potential of synthesized novel 2-substituted 4-anilinoquinazolines as quinazoline-pyrrole hybrids in MCF-7 human breast cancer cell line and A-549 human lung adenocarcinoma cell lines

Background

A series of novel 2 substituted 4-anilinoquinazolines-pyrrole hybrids were synthesized, and cytotoxic activity were evaluated using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay.

Methods

The cell line used for the activity was MCF-7 breast cancer cell line and A459 human lung adenocarcinoma cell line. The newly quinazoline-pyrrole hybrid compounds have been synthesized from the 4-chloro-7-(3-chloropropoxy)-6-methoxy-2-phenylquinazoline derivatives. The chemical structure of the synthesized compounds has been confirmed by FTIR, 1HNMR, 13C NMR, and mass spectral data. The cytotoxic study was conducted using morphological study and MTT assay against adenocarcinoma and human breast cancer cell lines.

Results

The results of cytotoxic evaluation revealed that few compounds show moderate to promising activity when compared with standard doxorubicin (IC50 value 41.05 μM at 72 h). The synthesized compounds 7d and 7f were found effective in breast cancer cell line with IC50 values 40.64 μM and 44.98 μM at 72 h, respectively. The synthesized compounds 7d, 7f, 7g, and 7h were found effective in adenocarcinoma cell line with IC50 values of 41.05 μM, 45.54 μM, 46.93 μM, and 48.62 μM, respectively.

Conclusion

Based on the experimental evidences, we proposed structure activity relationship to provide significant information for the design and development of further potent anticancer agents.

Design, Synthesis, and Biological Evaluation of 1,2,4-Thiadiazole-1,2,4-Triazole Derivatives Bearing Amide Functionality as Anticancer Agents

A novel library of amide functionality having 1,2,4-thiadiazole-1,2,4-triazole (8a–j) analogs was designed, synthesized, and structures were characterized by ¹H NMR, ¹³C NMR, and mass (ESI–MS) spectral data. Further, all compounds were evaluated for their anticancer activities against four different cancer cell lines including breast cancer (MCF-7, MDA MB-231), lung cancer (A549), and prostate cancer (DU-145) by MTT reduction assay method, and etoposide acts as a standard drug. The results confirmed that majority of the synthesized compounds showed moderate to potent anticancer activities aligned with four cell lines. Among the synthesized compounds, 8b, 8c, 8d, 8e, 8g and 8i displayed more potent activity along with inhibitory concentration values ranging from 0.10 ± 0.084 to 11.5 ± 6.49 µM than the standard IC₅₀ values, which ranges from 1.91 ± 0.84 to 3.08 ± 0.135 µM, respectively.

Novel 1,3,4-Oxadiazole Fused Thiadiazole Derivatives: Synthesis and study of Anticancer Activities

Background:

In search of novel anticancer agents, a series of 1,3,4-oxadiazole derivatives (12a-j) containing 1,3,4-thiadiazole moieties were synthesized, and their structures were confirmed by 1HNMR, 13CNMR and ESI-MS spectral analysis.

Methods:

Cytotoxicity of these compounds was evaluated by MTT assay in vitro against four human tumor cell lines, i.e. A549 (lung), MCF-7 (breast), A375 (melanoma) and HT-29 (colon).

Results:

Here, CA4 used as positive control. Among them, compounds 12b, 12c, 12f, 12g, 12h and 12j were exhibited promising activity than control drug.

Conclusion:

In conclusion, we have synthesized a novel series of 1,3,4-oxadiazole fused 1,3,4- thiazdiazole derivatives and their structures were confirmed by spectral analysis.

Synthesis, antiproliferative and apoptosis induction potential activities of novel bis(indolyl)hydrazide-hydrazone derivatives

In recent years, indole-indazolyl hydrazide-hydrazone derivatives with strong cell growth inhibition and apoptosis induction characteristics are being strongly screened for their cancer chemo-preventive potential. In the present study, N-methyl and N,N-dimethyl bis(indolyl)hydrazide-hydrazone analog derivatives were designed, synthesized and allowed to evaluate for their anti-proliferative and apoptosis induction potential against cervical (HeLa), breast (MCF-7 and MDA-MB-231) and lung (A549) cancer cell lines relative to normal HEK293 cells. The MTT assay in conjunction with mitochondrial potential assays and the trypan blue dye exclusion were employed to ascertain the effects of the derivatives on the cancer cells. Further, mechanistic studies were conducted on compound 14a to understand the biochemical mechanisms and functional interactions with various signaling pathways triggered in HeLa and MCF-7 cells. Compound 14a induced apoptosis via caspase independent pathway through the participation of mitogen-activated protein kinases (MAPK) such as extracellular signal related kinase (ERK) and p38 as well as p53 pathways. It originates the activation of pro-apoptotic proteins such as Bak and Mcl-1s and also strongly induced the generation of reactive oxygen species. In downstream signaling pathway, activated p53 protein interacted with MAPK pathways, including SAPK/c-Jun N-terminal protein kinase (JNK), p38 and ERK kinases resulting in apoptotic cell death. The involvement of MAPK cascades such as p38, ERK and p38 on compound 14a induced apoptotic cell death was evidenced by the fact that the inclusion of specific inhibitors of p38, ERK1/2 and JNK MAPK (SB2035809, PD98059 and SP600125) prevented the compound 14a towards induced apoptosis. The results clearly showed that MAP kinase cascades were crucial for apoptotic response in compound 14a induced cellular killing and were dependent on p53 activity. Based on the results, compound 14a was identified as a promising candidate for cancer therapeutics and these findings furnish a basis for further in vivo experiments on anti-proliferative activity.

Synthesis of New 1,3,5-Triazine-Based 2-Pyrazolines as Potential Anticancer Agents

A new series of 1,3,5-triazine-containing 2-pyrazoline derivatives (8⁻11)a⁻g was synthesized by cyclocondensation reactions of [(4,6-bis((2-hydroxyethyl)amino)-1,3,5-triazin-2-yl)amine]chalcones 7a⁻g with hydrazine hydrate and derivatives. Chalcones 7a⁻g were obtained by Claisen-Schmidt condensation between aromatic aldehydes and triazinic derivative 5, which was synthesized in high yield by a microwave-assisted reaction. Seventeen of the synthesized compounds were selected and tested by the US National Cancer Institute (NCI) for their anticancer activity against 58 different human tumor cell lines. Compounds 7g and 10d,e,g showed important GI50 values ranging from 0.569 to 16.6 µM and LC50 values ranging from 5.15 to >100 µM.