Design, synthesis, in vitro and in silico evaluations of new isatin-triazine- aniline hybrids as potent anti- Alzheimer multi-target directed lead compounds.

Multi target directed ligands (MTDLs) are one of the promising tools for treatment of complex disease like Alzheimer's disease (AD). In this study, using rational design, we synthesized new 15 hybrids of the s-triazine, isatin and aniline derivatives as anti- AD compounds. The design was as way as that new compounds could had anti cholinesterase (ChE), antioxidant and biometal chelation ability. In vitro biological evaluation against ChE enzymes showed that these molecules were excellent inhibitors with IC50 values ranging from 0.2 nM to 734.5 nM for acetylcholinesterase (AChE), and 0.02 µM to 1.92 µM for butyrylcholinesterase (BChE). Among these compounds, 8 l with IC50 AChE = 0.7 nM, IC50 BChE = 0.09 µM and 8n with IC50 AChE = 0.2 nM, IC50 BChE = 0.03 µM were the most potent compounds. In silico studies showed that these molecules had key and effective interactions with the corresponding enzymes residues. The molecules with hydroxyl group on aniline moiety had also good antioxidant activity with EC50 values ranging from 64.2 µM to 103.6 µM. The UV-Vis spectroscopy study revealed that molecule 8n was also able to chelate biometals such as Zn2+, Cu2+and Fe2+ properly. It was concluded that these molecules could be excellent lead compounds for future studies.

Thiazolyl-isatin derivatives: Synthesis, in silico studies, in vitro biological profile against breast cancer cells, mRNA expression, P-gp modulation, and interactions of Akt2 and VIM proteins.

The literature reports that thiazole and isatin nuclei present a range of biological activities, with an emphasis on anticancer activity. Therefore, our proposal was to make a series of compounds using the molecular hybridization strategy, which has been used by our research group, producing hybrid molecules containing the thiazole and isatin nuclei. After structural planning and synthesis, the compounds were characterized and evaluated in vitro against breast cancer cell lines (T-47D, MCF-7 and MDA-MB-231) and against normal cells (PBMC). The activity profile on membrane proteins involved in chemoresistance and tumorigenic signaling proteins was also evaluated. Among the compounds tested, the compounds 4c and 4a stood out with IC50 values of 1.23 and 1.39 µM, respectively, against the MDA-MB-231 cell line. Both compounds exhibited IC50 values of 0.45 µM for the MCF-7 cell line. Compounds 4a and 4c significantly decreased P-gp mRNA expression levels in MCF-7, 4 and 2 folds respectively. Regarding the impact on tumorigenic signaling proteins, compound 4a inhibited Akt2 in MDA-MB-231 and compound 4c inhibited the mRNA expression of VIM in MCF-7.

Isatin thiazoles as antidiabetic: Synthesis, in vitro enzyme inhibitory activities, kinetics, and in silico studies.

Diabetes mellitus is one of the most prevalent diseases nowadays. Several marketed drugs are available for the cure and treatment of diabetes, but there is still a dire need of introducing compatible drug molecules with lesser side effects. The current study is based on the synthesis of isatin thiazole derivatives 4-30 via the Hantzsch reaction. The synthetic compounds were characterized using different spectroscopic techniques and evaluated for their α-amylase and α-glucosidase inhibition potential. Of 27 isatin thiazoles, five (4, 5, 10, 12, and 16) displayed good activities against the α-amylase enzyme with IC50 values in the range of 22.22 ± 0.02-27.01 ± 0.06 µM, and for α-glucosidase, the IC50 values of these compounds were in the range of 20.76 ± 0.17-27.76 ± 0.17 µM, respectively. The binding interactions of the active molecules within the active site of enzymes were studied with the help of molecular docking studies. In addition, kinetic studies were carried out to examine the mechanism of action of the synthetic molecules as well. Compounds 3a, 4, 5, 10, 12, and 16 were also examined for their cytotoxic effect and were found to be noncytotoxic. Thus, several molecules were identified as good antihyperglycemic agents, which can be further modified to enhance inhibition ability and to find the lead molecule that can act as a potential antidiabetic agent.

Design, synthesis, and biological evaluation of novel morpholinated isatin-quinoline hybrids as potent anti-breast cancer agents.

Keeping in view the emerging need for potent and safer anti-breast cancer agents as well as the pharmacological attributes of isatin, quinolone, and morpholine derivatives, novel hydrazine-linked morpholinated isatin-quinoline hybrids were designed, synthesized, and evaluated as anti-breast cancer agents. The synthesized hybrid compounds were preliminarily screened against two breast cancer cell lines (MCF-7 and MDA-MB-231). Almost all synthetics showed potent inhibitory potential against hormone-positive MCF-7 cells while being inactive against hormone-negative MDA-MB-231 cells. Potent compounds were further evaluated against the L929 (noncancerous skin fibroblast) cell line and found to be highly selective for MCF-7 cells over L929 cells. Cell cycle analysis confirmed that the most potent compound AS-4 (MCF-7: GI50 = 4.36 µM) causes mitotic arrest at the G2 /M phase. Due to higher selectivity toward estrogen receptor alpha (ERα)-dependent MCF-7 cells, various binding interactions of AS-4 with ERα are also streamlined, suggesting the capability of AS-4 to completely block ERα. Overall, the study suggests that AS-4 can act as a potential lead for further development of potent and safer anti-breast cancer agents.

Synthesis, biological evaluation, and in silico studies of potential activators of apoptosis and carbonic anhydrase inhibitors on isatin-5-sulfonamide scaffold.

Carbonic anhydrase IX is a promising target for the search for new antitumor compounds with improved properties. Using the molecular hybridization approach, on the basis of structures of a selective carbonic anhydrase IX inhibitor 3 and an activator of apoptosis 2 (1), a series of 1-substituted isatin-5-sulfonamides 5a-5u were designed and synthesized. The study of the inhibitory activity of isatin-5-sulfonamides showed the ability to inhibit I, II, IX, XII isoforms at nano- and micromolar concentrations. Docking of compounds 5e and 5k into the active site of II and IX carbonic anhydrase isoforms showed the coordination of sulfonamidate anions with zinc cations, as well as a number of additional hydrophobic interactions. The trifluoromethylthio derivative 5r suppressed the growth of tumor cells at low micromolar concentrations, maintaining activity on resistant lines and under hypoxic conditions. Immunoblotting of MCF7 cells treated with the 5r revealed its antiestrogenic activity and ability to activate apoptosis in tumor cells.

Synthesis, spectroscopic investigation, crystal structure analysis, quantum chemical study, biological activity and molecular docking of three isatin derivatives.

Three isatin derivatives, namely, 1-allyl-3-hydroxy-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C17H17NO3, 1-ethyl-3-hydroxy-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C16H17NO3, and 5-bromo-3-hydroxy-1-methyl-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C15H14BrNO3, were synthesized, crystallized by the slow-evaporation technique, characterized by 1H and 13C NMR spectroscopy, and analysed by the single-crystal X-ray diffraction (XRD) method. Quantum chemical parameters, such as the energy of the highest occupied molecular orbital, energy of the lowest unoccupied molecular orbital, energy gap, electronic energy, ionization potential, chemical potential, global hardness, global softness and electrophilicity index, were calculated. The druglikeness and bioactivity scores of the compounds were calculated. The activities of these isatin derivatives against bacterial strains, such as Eschericia coli, Proteus vulgaris, Shigella flexneri, Staphylococcus aureus and Micrococcus luteus, and the fungal strain Aspergillus niger, were determined using the well-diffusion assay method. Molecular docking studies were carried out to predict the binding mode of the isatin compounds with the penicillin binding protein enzyme and to identify the interactions between the enzyme and the ligands under study.

Recent Advancement of Synthesis of Isatins as a Versatile Pharmacophore: A review.

Isatin (1 H-indole-2, 3-Dione) and its derivatives are versatile compounds which acts as a precursor for a large number of pharmacologically active compounds. Therefore isatins have a significant importance in the synthesis of different heterocyclic compounds. Isatins show variety of biological activities. In this review we focus on synthetic methods of isatins and their biological activities such as antimicrobial, anticonvulsant, anti-inflammatory and analgesic activity, antitubercular activity.

Isatin Hybrids and Their Pharmacological Investigations.

Hybridization is an important strategy to design molecules that can be effectively used to treat fatal diseases known to mankind. Molecular hybrids and their pharmacological investigations aided in discovering several potent isatin (Indole 2, 3 dione) derivatives with anti-HIV, antimalarial, antitubercular, antibacterial, and anticancer activities. Indole-2,3-dione and their derivatives have diverse pharmacological properties and have a prominent role in the discovery of new drugs. To understand the various approaches for designing new molecules based on isatin nucleus analysis of various pharmacophore hybrids, spacers/linkers between pharmacophores and isatin for hybridization and their biological activities are important. This review discusses the progress in developing isatin hybrids as biologically effective agents and their crucial aspects of design and structure-activity relationships.

Design and synthesis of novel isatin-based derivatives targeting cell cycle checkpoint pathways as potential anticancer agents.

In recent years, cell cycle and checkpoint pathways regulation are offering new therapeutic approaches against cancer. Isatin, is a well exploited scaffold in the anticancer domain. Accordingly, the current work describes the design and synthesis of two series of (Z)-3-substituted-2-(((E/Z)-5-substituted-2-oxo-1-substituted-indolin-3-ylidene)hydrazinylidene)-thiazolidin-4-ones, 4(a-s) and (E/Z)-1-substituted-3-(((Z)-3-substituted-4-methylthiazol-2(3H)-ylidene)hydrazineylidene)-5-substituted-indolin-2-ones, 5(a-s). The structures of the synthesized molecules were confirmed by spectral and elemental methods of analyses. Pure diastereomers were further identified with 1H-1H-NOESY and confirmed with X-ray crystallography. The target compounds were tested in vitro for their cytotoxicity against three human epithelial cell lines, liver (HepG2), breast (MCF-7), and colon (HT-29) in addition to the diploid human normal cells (WI-38) compared to doxorubicin as a reference drug. Variable cytotoxic effects (IC50 3.29-100 µmol) were reported on the three cancer cell lines with pronounced selectivity compared to the normal one WI-38. The potency of the most active compounds, 4o, 4s, 5e, 5f, 5l, 5m and 5o (IC50 3.29-9.92 µmol), in both series associated with the (Z) configurations of N = thiazolidin/ene or one, however, the configuration of the N = isatin moiety seemed to be of no importance to the activity. The tested compounds were grouped for their possible mechanism of action into 4 categories. Compound 4o with no apparent effect on all genes examined. Compounds 4s and 5o affected all genes investigated and seem to have multiple cellular targets; induced the expression of p53 and caspases, and downregulated that of CDK1. Compounds 5l and 5m directly elevated the expression of initiator and effector caspases without going through p53 pathway. Finally, compounds 5e and 5f elevated the expression of p53 and inhibited CDK1. Compounds 4s, 5e, 5f, 5l, 5m, and 5o caused a significant elevation in the activity of cleaved caspase 3 as well. Docking studies on CDK1 revealed that the active molecules bind to the tested enzyme by the same manner of the co-crystallized ligands and the isatin-thiazoldinone/ene scaffold is essential for binding of these molecules.

Potent inhibitors of SARS-CoV-2 3C-like protease derived from N-substituted isatin compounds.

SARS-CoV-2 3C-like protease is the main protease of SARS-CoV-2 and has been considered as one of the key targets for drug discovery against COVID-19. We identified several N-substituted isatin compounds as potent SARS-CoV-2 3C-like protease inhibitors. The three most potent compounds inhibit SARS-CoV-2 3C-like protease with IC50's of 45 nM, 47 nM and 53 nM, respectively. Our study indicates that N-substituted isatin compounds have the potential to be developed as broad-spectrum anti-coronavirus drugs.

Novel scaffold hopping of potent benzothiazole and isatin analogues linked to 1,2,3-triazole fragment that mimic quinazoline epidermal growth factor receptor inhibitors: Synthesis, antitumor and mechanistic analyses.

A series of benzothiazole/isatin linked to 1,2,3-triazole moiety and terminal sulpha drugs 5a-e and 6a-e were synthesized and evaluated for cytotoxic activity against a panel of cancer cell lines. The novel compounds showed variable IC50 range of activity and some of them were potent compared to reference drug. The promising compounds were subjected as postulated the mimicry proposal for quinazoline-based EGFR inhibitors for their inhibitory profile against EGFR TK enzyme. That data obtained revealed that most of these compounds were potent EGFR TK inhibitors at nanomolar concentrations. Among these, compounds 5a and 5b showed more potent activity on EGFR compared to erlotinib (IC50 103 and 104 versus 67.6 nM). Based upon the results, molecular docking analysis was performed on EGFR receptor and proved the strong contribution of fragments; benzothiazole, isatin, and triazole to the binding ATP pocket. When these selected compounds 5a and 5b were tested in an HepG2 model, they could effectively inhibited tumor growth, strongly induced cancer cell apoptosis, and suppressed cell cycle progression leading to DNA fragmentation. Well-DMET profile of the most active derivatives was presented and compared to the reference drugs. Taken together, we introduced novel triazole-sulpha drug hybrid for the first time as EGFR inhibitors and the results of our studies indicate that the newly discovered inhibitors have significant potential for anticancer treatment.

p-TSA.H2O mediated one-pot, multi-component synthesis of isatin derived imidazoles as dual-purpose drugs against inflammation and cancer.

A novel one-pot multicomponent reaction was performed to synthesize different imidazole and benzotriazole (BTA) isatin-based medicinally important compounds using (p-TSA·H2O) as an economical and operative acid catalyst. The yield of the products was found to be up to a maximum of 92% when using this catalyst. Antioxidant, anti-breast cancer and anti-inflammatory activities of these 13 isatin-based derivatives (named as 5a-m) were assessed. The inhibitory effects of these compounds were tested in vitro against cyclooxygenase-2 (COX-2, an enzyme responsible for inflammation) and phosphoinositide-3 kinase (PI3K, a key enzyme in breast cancer). "Among the 13 isatin-based Imidazole derivatives, five compounds (5a, 5d, 5f, 5 k and 5l) were found to exhibit anti-inflammatory as well as anti-cancer activity, which was validated using HRBC stabilization assay (to show anti-inflammatory activity) and cytotoxicity in MCF-7 (breast cancer cell line) to provide proof for anti-cancer property of the compounds". The molecular interactions between the two enzymes were probed using molecular docking. Structure-Activity Relationship (SAR) and ADMET prediction results were also useful to screen the most effective imidazole derivatives and to establish them as putative COX-2 inhibitors/anti-inflammatory drugs. These selected compounds which showed appreciable activity against COX-2 and PI3K are promising drug candidates for the treatment of breast cancer and inflammation which is often associated with breast cancer pathophysiology.

The Anti-Breast Cancer Potential of Bis-Isatin Scaffolds.

AIM: To develop novel anti-breast cancer agents and discuss the structure-activity relationship of bis-isatin scaffolds. BACKGROUND: Breast cancer is the most common invasive cancer and the second leading cause of cancer death in women after lung cancer. Bis-isatin scaffolds possess potential anti-breast cancer activity, and some of them such as Indirubin could induce cancer cells apoptosis via multiply mechanisms. OBJECTIVE: The primary objective of this study was to evaluate the potential of bis-isatin scaffolds with alkyl/ether linkers between the two isatin moieties against different human breast cancer cell lines including MCF-7, AU565, MDA-MB-231, MDA-MB-435 and MDA-MB-468 cells. METHODS: The synthesized bis-isatin scaffolds with alkyl/ether linker between the two isatin moieties were evaluated for their in vitro activity against MCF-7, AU565, MDA-MB-231, MDA-MB-435, and MDA-MB-468 human breast cancer cell lines by MTT assay. RESULTS: All the synthesized compounds (IC50: 38.3-197.6 µM) possess considerable activity against MCF-7, AU565, MDA-MB-231, MDA-MB-435, and MDA-MB-468 human breast cancer cell lines, and the most potent compound 4e (IC50: 38.3-63.5 µM) was no inferior to Cisplatin (IC50: 20.1-38.6 µM) against the five tested human breast cancer cell lines. CONCLUSION: All the synthesized bis-isatin scaffolds were active against a panel of breast cancer cell lines, highlighting the significance of exploring the bis-isatin scaffolds to fight against breast cancers. The enriched structure-activity relationship may set up the direction for the rational design and development of novel bis-isatin scaffolds with higher efficiency.

Synthesis, anti-proliferative activity, theoretical and 1H NMR experimental studies of Morita-Baylis-Hillman adducts from isatin derivatives.

Quaternary or spirocyclic 3-substituted-3-hydroxy-2-oxindole is considered a privileged scaffold. In other words, it is a molecular core present on several compounds with a wide spectrum of biological activities. Among its precursors, activated ketones (isatin nucleus) can be used as interesting starting points to Morita-Baylis-Hillman adducts derivatives, a class of compounds with good cytotoxic potential. In this paper, we present the synthesis, anti-proliferative activity against lung cancer cell line and a theoretical conformational study of 21 of Morita-Baylis-Hillman adducts from isatin derivatives, by DFT quantum chemical calculations, followed by a SAR and QSAR analysis. Besides, an efficient synthetic protocol and good biological activity profile were highlighted interesting observations about 1H NMR experimental spectra, molecular modeling results and crystallographic data available.

One-Pot Radiosynthesis and Biological Evaluation of a Caspase-3 Selective 5-[123,125I]iodo-1,2,3-triazole derived Isatin SPECT Tracer.

Induction of apoptosis is often necessary for successful cancer therapy, and the non-invasive monitoring of apoptosis post-therapy could assist in clinical decision making. Isatins are a class of compounds that target activated caspase-3 during apoptosis. Here we report the synthesis of the 5-iodo-1,2,3-triazole (FITI) analog of the PET tracer [18F]ICMT11 as a candidate tracer for imaging of apoptosis with SPECT, as well as PET. Labelling with radioiodine (123,125I) was achieved in 55 ± 12% radiochemical yield through a chelator-accelerated one-pot cycloaddition reaction mediated by copper(I) catalysis. The caspase-3 binding affinity and selectivity of FITI compares favourably to that of [18F]ICMT11 (Ki = 6.1 ± 0.9 nM and 12.4 ± 4.7 nM, respectively). In biodistribution studies, etoposide-induced cell death in a SW1222 xenograft model resulted in a 2-fold increase in tumour uptake of the tracer. However, the tumour uptake was too low to allow in vivo imaging of apoptosis with SPECT.

Synthesis and bioevaluation of novel steroidal isatin conjugates derived from epiandrosterone/androsterone.

Steroids are classes of natural products widely distributed in nature, which have been demonstrated to exhibit broad biological functions, and have also attracted increasing interest from bioorganic and pharmaceutical researches. In order to develop novel chemical entities as potential cytotoxic agents, a series of steroidal isatin conjugations derived from epiandrosterone and androsterone were efficiently prepared and characterized, and all these obtained compounds were screened for their potential cytotoxic activities. The preliminary bioassay indicated that most of the newly synthesized compounds exhibited good cytotoxic activities against human gastric cancer (SGC-7901), melanoma (A875), and hepatocellular liver carcinoma (HepG2) cell lines compared with 5-fluorouracil (5-FU), which might be considered as promising scaffold for further development of potential anticancer agents.

Experimental and Computational Evaluation of Piperonylic Acid Derived Hydrazones Bearing Isatin Moieties as Dual Inhibitors of Cholinesterases and Monoamine Oxidases.

A set of piperonylic acid derived hydrazones with variable isatin moieties was synthesized and evaluated for their inhibitory activity against the enzymes acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and monoamine oxidases A and B (MAO-A/B). The results of in vitro studies revealed IC50 values in the micromolar range, with the majority of the compounds showing selectivity for the MAO-B isoform. N-[2-Oxo-1-(prop-2-ynyl)indolin-3-ylidene]benzo[d][1,3]dioxole-5-carbohydrazide (3) was identified as a lead AChE inhibitor with IC50 =0.052±0.006 µm. N-[(3E)-5-chloro-2-oxo-2,3-dihydro-1H-indol-3-ylidene]-2H-1,3-benzodioxole-5-carbohydrazide (2) was the lead MAO-B inhibitor with IC50 =0.034±0.007 µm, and showed 50 times greater selectivity for MAO-B over MAO-A. The kinetic studies revealed that compounds 2 and 3 displayed competitive and reversible inhibition of AChE and MAO-B, respectively. The molecular docking studies revealed the significance of hydrophobic interactions in the active site pocket of the enzymes under investigation. Further optimization studies might lead to the development of potential neurotherapeutic agents.

Synthesis, antioxidant activity and SAR study of novel spiro-isatin-based Schiff bases.

A new series of 21 Schiff bases of spiro-isatin was synthesized, and their DPPH, CUPRAC and ABTS cation radical scavenging abilities were investigated for antioxidant activity. The results showed that all the synthesized compounds exhibited antioxidant activity for each assay. 5̍-(2,3-Dihydroxybenzylideneamino)spiro[[1,3] dioxolane-2,3̍-indoline]-2̍-on (5c) (IC50 = 4.49 µM, for DPPH; IC50 = 0.39 µM, for ABTS.+; and A0.50 = 0.42 µM, for CUPRAC) showed significantly better ABTS, CUPRAC and DPPH radical scavenging ability than quercetin (IC50 = 8.69 µM, for DPPH; IC50 = 15.49 µM, for ABTS.+; and A0.50 = 18.47 µM, for CUPRAC), which is used as a standard. SAR study showed that the synthesized compounds had higher ABTS.+ activity than DPPH and CUPRAC activities. Moreover, the compounds (5c and 5d), containing two hydroxyl groups, exhibited the highest antioxidant activities for all assays. Quantum chemical calculations were also carried out to support SAR results.

Highly Potent 1H-1,2,3-Triazole-Tethered Isatin-Metronidazole Conjugates Against Anaerobic Foodborne, Waterborne, and Sexually-Transmitted Protozoal Parasites.

Parasitic infections like amebiasis, trichomoniasis, and giardiasis are major health threats in tropical and subtropical regions of the world. Metronidazole (MTZ) is the current drug of choice for amebiasis, giardiasis, and trichomoniasis but it has several adverse effects and potential resistance is a concern. In order to develop alternative antimicrobials, a library of 1H-1,2,3-triazole-tethered metronidazole-isatin conjugates was synthesized using Huisgen's azide-alkyne cycloaddition reaction and evaluated for their amebicidal, anti-trichomonal, and anti-giardial potential. Most of the synthesized conjugates exhibited activities against Trichomonas vaginalis, Tritrichomonas foetus, Entamoeba histolytica, and Giardia lamblia. While activities against T. vaginalis and T. foetus were comparable to that of the standard drug MTZ, better activities were observed against E. histolytica and G. lamblia. Conjugates 9d and 10a were found to be 2-3-folds more potent than MTZ against E. histolytica and 8-16-folds more potent than MTZ against G. lamblia. Further analysis of these compounds on fungi and bacteria did not show inhibitory activity, demonstrating their specific anti-protozoal properties.

Scaffold hopping-guided design of some isatin based rigid analogs as fatty acid amide hydrolase inhibitors: Synthesis and evaluation.

Fatty acid amide hydrolase (FAAH) represents a potential therapeutic target for number of peripheral and nervous system related disorders including neuropathic pain and neuroinflammation. A library of N-(2,4-dichlorobenzoyl) isatin Schiff bases 7a-7l and 8a-8c were designed using the contemporary scaffold-hopping approach, synthesized and investigated for their ability to inhibit human FAAH enzyme using fluorescence based Cayman assay kit. The synthesized compounds inhibited FAAH with IC50 values in the range from 1.49 to 12,858 µM. Compound, 3-(1H-benzoimidazol-2-ylimino)-1-(2,4-dichlorobenzoyl)indolin-2-one (8c) showed strong inhibition against FAAH with IC50 of 1.49 ± 0.03 µM. SAR studies revealed various structural aspects important for the potency of these analogs. In particular, our findings suggested the requirement of hydrophobic aryl/heteroaryl moiety at C-3 position of isatin for optimum rigidity and steric hindrance to the scaffold. Additionally, molecular docking studies supported the experimental results revealing that compound 8c well-occupied the enzymatic cleft with optimal binding orientation and interactions within the active site of FAAH which resulted in reduced susceptibility of compound to nucleophilic attack and prevented it from leaving the active site, thereby increasing the inhibition. Also, compound 8c presented potent antidepressant and anxiolytic properties without any neurotoxicity. In silico molecular properties and ADMET descriptors calculations related the lead FAAH inhibitor 8c presented the satisfactory drug-like characteristics and ADMET properties and thus considered for further optimization. To the best of our knowledge this is the first report on the FAAH inhibitory properties of isatin-based analogs, revealing that both indoline skeleton and heteroaryl substitution at C-3 can modulate the activity of FAAH enzyme. In conclusion, the present study provided a better understanding of the molecular fragments requisite for maintaining and/or improving FAAH inhibition activity.