Preclinical Study of Immunological Isoxazole Derivatives as a Potential Support for Melanoma Chemotherapy.

(1) Background: Melanoma is an aggressive neoplasm derived from melanocyte precursors with a high metastatic potential. Responses to chemotherapy and immunotherapy for melanoma remain weak, underlining the urgent need to develop new therapeutic strategies for the treatment of melanoma. (2) Methods: The viability of NHDF and A375 cell cultures after the administration of the tested isoxazole derivatives was assessed after 24-h and 48-h incubation periods with the test compounds in the MTT test. ROS and NO scavenging analyses, a glycoprotein-P activity analysis, a migration assay, a test of apoptosis, and a multiple-criteria decision analysis were also performed. (3) Results: All compounds that were tested resulted in a slower migration of melanoma neoplastic cells. The mechanism of the antitumor activity of the tested compounds was confirmed-i.e., the pro-apoptotic activity of the compounds in A375 cell cultures. Compound O7K qualified for further research. (4) Conclusions: All the tested compounds inhibited the formation of melanoma metastases and demonstrated the ability to reduce the risk of developing drug resistance in the tumor. The MCDA results showed that O7K showed the strongest antitumor activity.

Design and Synthesis of Novel Anti-inflammatory/Anti-ulcer Hybrid Molecules with Antioxidant Activity.

BACKGROUND: NSAIDs are the most widely prescribed medications worldwide for their anti-inflammatory, antipyretic, and analgesic effects. However, their chronic use can lead to several adverse drug events including GI toxicity. The selective COX-2 inhibitors developed as gastrosparing NSAIDs also suffer from serious adverse effects which limit their efficacy. OBJECTIVE: Local generation of reactive oxygen species is implicated in NSAID-mediated gastric ulceration and their combination with H2 antagonists like famotidine reduces the risk of ulcers. The objective of this work was to design and synthesize novel methanesulphonamido isoxazole derivatives by hybridizing the structural features of NSAIDs with those of antiulcer drugs (ranitidine, famotidine, etc.) to utilize a dual combination of anti-inflammatory activity and reducing (antioxidant) potential. METHODS: The designing process utilized three dimensional similarity studies and utilized an isoxazole core having a potential for anti-inflammatory as well as radical scavenging antioxidant activity. The compounds were assayed for their anti-inflammatory activity in established in vivo models. The in vitro antioxidant activity was assessed in potassium ferricyanide reducing power (PFRAP) assay employing ascorbic acid as the standard drug. RESULTS: Compounds 5, 6, 9 and 10 showed antiinflammatory activity comparable to the standard drugs and were also found to be non-ulcerogenic at the test doses. Compounds 6-10 exhibited good antioxidant effect in the concentration range of 1.0- 50.0 µmol/ml. The test compounds were also found to comply with the Lipinski rule suggesting good oral absorption. CONCLUSION: A new series of isoxazole based compounds is being reported with good antiinflammatory activity coupled with antioxidant potential as gastro-sparing anti-inflammatory agents.

Synthesis of Isoxazolines by the Electrophilic Chalcogenation of ß,γ-Unsaturated Oximes: Fishing Novel Anti-Inflammatory Agents.

Herein, we describe a new strategy to prepare chalcogen-functionalized isoxazolines. The strategy involves the reaction of ß,γ-unsaturated oximes with electrophilic selenium and tellurium species, affording 19 new selenium- and tellurium-containing isoxazolines in good yields after 1 h at room temperature. The method was efficiently extended to the synthesis of 5 new (bis)isoxazoline ditellurides. One of the prepared compounds, 3-phenyl-5-((phenylselanyl)methyl)-isoxazoline, demonstrated better anti-inflammatory and antiedematogenic effects than the reference drug Celecoxib.

Identification of a potent benzoxaborole drug candidate for treating cryptosporidiosis.

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children and causes chronic diarrhea in AIDS patients, but the only approved treatment is ineffective in malnourished children and immunocompromised people. We here use a drug repositioning strategy and identify a promising anticryptosporidial drug candidate. Screening a library of benzoxaboroles comprised of analogs to four antiprotozoal chemical scaffolds under pre-clinical development for neglected tropical diseases for Cryptosporidium growth inhibitors identifies the 6-carboxamide benzoxaborole AN7973. AN7973 blocks intracellular parasite development, appears to be parasiticidal, and potently inhibits the two Cryptosporidium species most relevant to human health, C. parvum and C. hominis. It is efficacious in murine models of both acute and established infection, and in a neonatal dairy calf model of cryptosporidiosis. AN7973 also possesses favorable safety, stability, and PK parameters, and therefore, is an exciting drug candidate for treating cryptosporidiosis.

Aminomethylene-Phosphonate Analogue as a Cu(II) Chelator: Characterization and Application as an Inhibitor of Oxidation Induced by the Cu(II)-Prion Peptide Complex.

Recently, we reported on a series of aminomethylene-phosphonate (AMP) analogues, bearing one or two heterocyclic groups on the aminomethylene moiety, as promising Zn(II) chelators. Given the strong Zn(II) binding properties of these compounds, they may find useful applications in metal chelation therapy. With a goal of inhibiting the devastating oxidative damage caused by prion protein in prion diseases, we explored the most promising ligand, {bis[(1H-imidazol-4-yl)methyl]amino}methylphosphonic acid, AMP-(Im)2, 4, as an inhibitor of the oxidative reactivity associated with the Cu(II) complex of prion peptide fragment 84-114. Specifically, we first characterized the Cu(II) complex with AMP-(Im)2 by ultraviolet-visible spectroscopy and electrochemical measurements that indicated the high chemical and electrochemical stability of the complex. Potentiometric pH titration provided evidence of the formation of a stable 1:1 [Cu(II)-AMP-(Im)2]+ complex (ML), with successive binding of a second AMP-(Im)2 molecule yielding ML2 complex [Cu(II)-(AMP-(Im)2)2]+ (log K' = 15.55), and log ß' = 19.84 for ML2 complex. The CuN3O1 ML complex was demonstrated by X-ray crystallography, indicating the thermodynamically stable square pyramidal complex. Chelation of Cu(II) by 4 significantly reduced the oxidation potential of the former. CuCl2 and the 1:2 Cu:AMP-(Im)2 complex showed one-electron redox of Cu(II)/Cu(I) at 0.13 and -0.35 V, respectively. Indeed, 4 was found to be a potent antioxidant that at a 1:1:1 AMP-(Im)2:Cu(II)-PrP84-114 molar ratio almost totally inhibited the oxidation reaction of 4-methylcatechol. Circular dichroism data suggest that this antioxidant activity is due to formation of a ternary, redox inactive Cu(II)-Prp84-114-[AMP-(Im)2] complex. Future studies in prion disease animal models are warranted to assess the potential of 4 to inhibit the devastating oxidative damage caused by PrP.

Synthesis, Screening and Docking Analysis of Hispolon Pyrazoles and Isoxazoles as Potential Antitubercular Agents.

BACKGROUND: Hispolons are natural products known to possess cytoprotective, antioxidant and anti-cancer activities. We have found recently anti TB activity in these compounds. Efforts were made to optimize the structure with bioisosteric replacement of 1,3-diketo functional group with the corresponding pyrazole and isoxazole moieties. OBJECTIVE: The goal of this paper is designing new hispolon isoxazole and pyrazole and the evaluation of their biological activities. METHODS: The designed compounds were prepared using classical organic synthesis methods. The anti- TB activity was evaluated using the MABA method. RESULTS: A total of 44 compounds were synthesized (1a- 1v and 2a-2v) and screened for anti TB activity and antibacterial activity. The compounds 1b and 1n showed the highest potency with MIC 1.6µg/mL against M. tuberculosis H37Rv. CONCLUSION: Bioisosteric replacement of 1,3-diketo functional group in hispolons with pyrazole or isoxazole rings have resulted in potent anti TB molecules. Docking simulations of these compounds on mtFabH enzyme resulted in a clear understanding of bioactivity profiles of these compounds. Docking scores are in good agreement with the anti TB activity obtained for these compounds. Computational studies and in vitro screening results indicate mtFabH as the probable target of these compounds.

Effects of new tetrahydroquinoline-isoxazole hybrids on bioenergetics of hepatocarcinoma Hep-G2 cells and rat liver mitochondria.

New molecular hybrids were synthesized by combining tetrahydroquinoline (THQ) and isoxazole (ISX) scaffolds, in search for chemical structures with improved pharmacological properties. Our tetrahydroquinoline (THQ) and isoxazole (ISX) hybrids differ in the X and Y substituents: FM53 (X = H; Y= H), FM49 (X = CH3; Y= OCH3), FM50 (X = Cl; Y= H) and FM48 (X = Cl; Y= OCH3). Aiming at exploring their bioactivity in liver cancer cells, in this paper we report the effect of four THQ-ISX hybrids on viability, respiration and oxidative stress in Hep-G2 human hepatoma cells. In addition, we measured the alterations induced by these compounds on oxygen uptake and respiratory chain enzymes in isolated mitochondria. Cell viability assay indicated that these THQ-ISX hybrids displayed antiproliferative activity on Hep-G2 cells. Among these, FM50 (IC50 = 5.2 ±â€¯1.9 µM) and FM53 (IC50 = 6.8 ±â€¯0.7 µM) had the highest cytotoxicity. These four hybrids also inhibited the Hep-G2 cells respiration in the uncoupled state, with FM50 decreasing all respiratory states (basal, leak, uncoupled). While only FM49 and FM53 altered the Hep-G2 cells redox function. In terms of mitochondrial bioenergetics, THQ-ISX hybrids decreased the oxygen consumption in state 3 (via complex I and II), and also inhibited NADH oxidase and NADH cytochrome c reductase enzyme activities. In these experiments, the structural homologues FM50 and FM53 had a remarkable inhibitory effect (~50%) with respect to FM49 and FM48. These results show that THQ-ISX hybrids are promising compounds for hepatoma cancer treatment and that the phenyl substituent (Y= H) in the ISX scaffold intensifies both, the cytotoxicity in Hep-G2 cells and, inhibition of electron transport through complex I of the mitochondrial respiratory chain.

Application of Virtual Screening to the Identification of New LpxC Inhibitor Chemotypes, Oxazolidinone and Isoxazoline.

This report summarizes the identification and synthesis of novel LpxC inhibitors aided by computational methods that leveraged numerous crystal structures. This effort led to the identification of oxazolidinone and isoxazoline inhibitors with potent in vitro activity against P. aeruginosa and other Gram-negative bacteria. Representative compound 13f demonstrated efficacy against P. aeruginosa in a mouse neutropenic thigh infection model. The antibacterial activity against K. pneumoniae could be potentiated by Gram-positive antibiotics rifampicin (RIF) and vancomycin (VAN) in both in vitro and in vivo models.

Synthesis of new anticancer and anti-inflammatory isoxazolines and aziridines from the natural (-)-deltoin.

OBJECTIVES: This work describes the synthesis, the bioactivity and the structure-activity relationship of new derivatives from a natural coumarin. METHODS: (-)-Deltoin 1 and the corresponding isoxazolines and aziridines were characterized by spectroscopic means. The cytotoxic (HTC-116, IGROV-1 and OVCAR-3 cancer cell lines) and 5-lipoxygenase activity of (-)-deltoin 1 and its structural analogues have been evaluated. KEY FINDINGS: The phytochemical investigation of the ethyl acetate extract of the flowers of Ferula lutea (Poir.) Maire has led to the isolation of (-)-deltoin 1. A series of new isoxazoline 2a,a'-2f,f' and aziridine 3a,a'-3e,e' derivatives have been prepared by 1,3-dipolar cycloaddition. It has been found that the derivatives 2a (IC50 = 3.3 ± 0.1 µm), 3a,a' (IC50 = 5.9 ± 0.1 µm), 3b,b' (IC50 = 6.1 ± 0.7 µm) and 3c,c' (IC50 = 7.3 ± 0.9 µm) bearing a phenyl isoxazoline, a phenylaziridine, a 4-methlphenylaziridine and a 4-methoxyphenylaziridine, respectively, are more cytotoxic than (-)-deltoin 1 (IC50 = 14.3 ± 0.2 µm). The diastereoisomers in mixture (2f,f') with a 6-chloropyridin-2-yl system have shown the best anti-5-lipoxygenase activity (% inhibition = 53.1 ± 4.8% at 200 µm). CONCLUSIONS: Some analogues have been found more bioactive than deltoin 1. Their activity has been related to the nature of the added heterocycles. It would be interesting to evaluate their in-vivo activity.

Synthesis and SAR of new isoxazole-triazole bis-heterocyclic compounds as analogues of natural lignans with antiparasitic activity.

Despite the impressive scientific and technological advances of recent decades, no effective treatment is currently available for Chagas disease. Our research group has been studying the design and synthesis of analogues of natural lignans aiming to identify compounds with antiparasitic activity. This article reports the synthesis of 42 novel bis-heterocyclic derivatives and the structure-activity relationship study conducted based on results of biological assays against Trypanosoma cruzi amastigotes. Thirty-seven compounds were active, and eight of them had GI50 values lower than 100 µM (GI50 88.4-12.2 µM). A qualitative structure activity relationship study using three dimensional descriptors was carried out and showed a correlation between growth inhibitory potency and the presence of bulky hydrophobic groups located at rings A and D of the compounds. Compound 3-(3,4-dimethoxyphenyl)-5-((4-(4-pentylphenyl)-1H-1,2,3-triazol-1-yl)methyl)isoxazole (31) was the most active in the series (GI50 12.2 µM), showing, in vitro, low toxicity and potency similar to benznidazole (GI50 10.2 µM). These results suggest that this compound can be a promising scaffold for the design of new trypanocidal compounds.

Garcinol, an effective monoamine oxidase-B inhibitor for the treatment of Parkinson's disease.

Loss of dopamine containing neurons in the substantia nigra pars compacta of midbrain, and resultant depletion of dopamine in the striatum is the cause of Parkinson's disease (PD), which is associated with motor abnormalities. Replenishment of dopamine by oral supplementation of its precursor, the levodopa (L-DOPA), remains the primary mode of treatment of PD, despite its potential side-effects after prolonged use in patients. To reduce the daily dosing of L-DOPA in patients, inhibitors of dopamine catabolizing enzymes, particularly monoamine oxidase-B (MAO-B), are prescribed. The most widely used MAO-B inhibitor to maintain the bioavailability of dopamine in the brain of PD patients is L-deprenyl, despite of its potential side-effects. The present study identified Garcinol as a potential candidate in the treatment paradigm of PD by virtue of its exorbitant MAO-B inhibitory potential. The inhibitory potential is comparable to the known MAO-B inhibitors, which was evaluated using molecular docking technique. Owing to its known antioxidant, anti-inflammatory and catechol-o-methyl transferase inhibitory potential, the molecule would confer neuroprotection as well, and thus, the present study is of immense significance in the treatment paradigm of PD.

Structure based virtual screening of the Ebola virus trimeric glycoprotein using consensus scoring.

Ebola virus (EBOV) causes zoonotic viral infection with a potential risk of global spread and a highly fatal effect on humans. Till date, no drug has gotten market approval for the treatment of Ebola virus disease (EVD), and this perhaps allows the use of both experimental and computational approaches in the antiviral drug discovery process. The main target of potential vaccines that are recently undergoing clinical trials is trimeric glycoprotein (GP) of the EBOV and its exact crystal structure was used in this structure based virtual screening study, with the aid of consensus scoring to select three possible hit compounds from about 36 million compounds in MCULE's database. Amongst these three compounds, (5R)-5-[[5-(4-chlorophenyl)-1,2,4-oxadiazol-3-yl]methyl]-N-[(4-methoxyphenyl)methyl]-4,5-dihydroisoxazole-3-carboxamide (SC-2, C21H19ClN4O4) showed good features with respect to drug likeness, ligand efficiency metrics, solubility, absorption and distribution properties and non-carcinogenicity to emerge as the most promising compound that can be optimized to lead compound against the GP EBOV. The binding mode showed that SC-2 is well embedded within the trimeric chains of the GP EBOV with molecular interactions with some amino acids. The SC-2 hit compound, upon its optimization to lead, might be a good potential candidate with efficacy against the EBOV pathogen and subsequently receive necessary approval to be used as antiviral drug for the treatment of EVD.

Synthesis of New Isoxazole-, Pyridazine-, Pyrimidopyrazines and Their Anti-Inflammatory and Analgesic Activity.

BACKGROUND: Isoxazoles, pyridazines, and pyrimidopyrazines have recently attracted attention due to their potent pharmacological activities. They exhibited anticancer, neuroprotective, analgesic and anti-inflammatory effects. OBJECTIVE: The study aimed to synthesize novel isoxazoles, pyridazines, and pyrimidopyrazines through efficient high yield protocol for evaluating their analgesics and anti-inflammatory activities. METHOD: A series of novel isoxazole-, pyridazine-, pyrimidopyrazine derivatives was prepared from 5,8-alkyl-1,3-dimethyl-5,6-dihydropyrimido[5,6-e]pyrazine-2,4,7-trione (1a,b) as the starting material. RESULTS: The prepared derivatives were synthesized in moderate to good yields (60-75%) in a stepwise efficient protocol under mild condition. These new compounds have been proven by several spectroscopic techniques as IR, 1D and 2D NMR techniques and mass analysis. The in vivo anti-inflammatory was assessed for the synthesized compounds using carrageenan-induced rat hind paw edema model. Also, the in vivo analgesic activity for these products was examined utilizing hot-plate and acetic acid-induced writhing response assays. CONCLUSION: The isoxazole derivatives (3a-f) showed the most forceful anti-inflammatory and analgesic activities. Pyrimidopyrazines (4a-f) demonstrated weaker but comparable antiinflammatory and analgesic activities to the positive controls.

Regiospecific Synthesis of Ring A Fused Withaferin A Isoxazoline Analogues: Induction of Premature Senescence by W-2b in Proliferating Cancer Cells.

Induction of premature senescence represents a novel functional strategy to curb the uncontrolled proliferation of malignant cancer cells. This study unveils the regiospecific synthesis of novel isoxazoline derivatives condensed to ring A of medicinal plant product Withaferin-A. Intriguingly, the cis fused products with ß-oriented hydrogen exhibited excellent cytotoxic activities against proliferating human breast cancer MCF7 and colorectal cancer HCT-116 cells. The most potent derivative W-2b triggered premature senescence along with increase in senescence-associated ß-galactosidase activity, G2/M cell cycle arrest, and induction of senescence-specific marker p21Waf1/Cip1 at its sub-toxic concentration. W-2b conferred a robust increase in phosphorylation of mammalian checkpoint kinase-2 (Chk2) in cancer cells in a dose-dependent manner. Silencing of endogenous Chk2 by siRNA divulged that the amplification of p21 expression and senescence by W-2b was Chk2-dependent. Chk2 activation (either by ectopic overexpression or through treatment with W-2b) suppressed NM23-H1 signaling axis involved in cancer cell proliferation. Finally, W-2b showed excellent in vivo efficacy with 83.8% inhibition of tumor growth at a dose of 25 mg/kg, b.w. in mouse mammary carcinoma model. Our study claims that W-2b could be a potential candidate to limit aberrant cellular proliferation rendering promising improvement in the treatment regime in cancer patients.

Functional reconstitution of cell-free synthesized purified Kv channels.

The study of ion channel activity and the screening of possible inhibitor molecules require reliable methods for production of active channel proteins, their insertion into artificial membranes and for the measurement of their activity. Here we report on cell-free expression of soluble and active Kv1.1 and Kv1.3 channels and their efficient insertion into liposomes. Two complementary methods for the determination of the electrical activity of the proteoliposome-embedded channels were compared using Kv1.1 as a model system: (1) single channel recordings in droplet interface bilayers (DIB) and (2) measurement of the membrane voltage potential generated by a potassium ion diffusion potential using the voltage-sensitive fluorescent dye oxonol VI. Single channel recordings in DIBs proved unreliable because of the non-reproducible fusion of proteoliposomes with an artificial membrane. Therefore, the use of the optical indicator oxonol VI was adapted for 96 well microtiter plates using the ionophore valinomycin as a positive control. The activity of Kv1.1 and Kv1.3 channels was then monitored in the absence and presence of different venom toxins, demonstrating that fluorescent dyes can be used very efficiently when screening small molecules for their channel blocking activity.

Lead Optimization Generates CYP11B1 Inhibitors of Pyridylmethyl Isoxazole Type with Improved Pharmacological Profile for the Treatment of Cushing's Disease.

Cushing's disease, characterized by elevated plasma cortisol levels, can be controlled by inhibition of 11ß-hydroxylase (CYP11B1). The previously identified selective and potent CYP11B1 inhibitor 5-((5-methylpyridin-3-yl)methyl)-2-phenylpyridine Ref 7 (IC50= 2 nM) exhibited promutagenic potential as well as very low oral bioavailability in rats (F = 2%) and was therefore modified to overcome these drawbacks. Successful lead optimization resulted in similarly potent and selective 5-((5-methoxypyridin-3-yl)methyl)-3-phenylisoxazole 25 (IC50 = 2 nM, 14-fold selectivity over CYP11B2), exhibiting a superior pharmacological profile with no mutagenic potential. Furthermore, compound 25 inhibited rat CYP11B1 (IC50 = 2 µM) and showed a high oral bioavailability (F = 50%) and sufficient plasma concentrations in rats, providing an excellent starting point for a proof-of-principle study.

Discovery of novel aminobenzisoxazole derivatives as orally available factor IXa inhibitors.

Using structure based drug design, novel aminobenzisoxazoles as coagulation factor IXa inhibitors were designed and synthesized. Highly selective inhibition of FIXa over FXa was demonstrated. Anticoagulation profile of selected compounds was evaluated by aPTT and PT tests. In vitro ADMET and pharmacokinetic (PK) profiles were also evaluated.

Synthesis of 3,5-Disubstituted Isoxazoles Containing Privileged Substructures with a Diverse Display of Polar Surface Area.

We designed and synthesized the molecular framework of 3,5-disubstituted isoxazoles containing privileged substructures with various substituents which uniquely display polar surface area in a diverse manner. A library of 3,5-disubstituted isoxazoles were systematically prepared via 1,3-dipolar cycloaddition of alkynes with nitrile oxides prepared by two complementary synthetic routes; method A utilized a halogenating agent with a base and method B utilized a hypervalent iodine reagent. Through the biological evaluation of corresponding isoxazoles via three independent phenotypic assays, the different pattern of biological activities was shown according to the type of privileged substructure and substituent. These results demonstrated the significance of molecular design via introducing privileged substructures and various substituents to make a diverse arrangement of polar surface area within a similar 3-dimensional molecular framework.

Discovery, design and synthesis of 6H-anthra[1,9-cd]isoxazol-6-one scaffold as G9a inhibitor through a combination of shape-based virtual screening and structure-based molecular modification.

Protein lysine methyltransferase G9a is widely considered as an appealing antineoplastic target. Herein we present an integrated workflow combining shape-based virtual screening and structure-based molecular modification for the identification of novel G9a inhibitors. The shape-based similarity screening through ROCS overlay on the basis of the structure of UNC0638 was performed to identify CPUY074001 contained a 6H-anthra[1,9-cd]isoxazol-6-one scaffold as a hit. Analysis of the binding mode of CPUY074001 with G9a and 3D-QSAR results, two series compounds were designed and synthesized. The derivatives were confirmed to be active by in vitro assay and the SAR was explored by docking stimulations. Besides, several analogues showed acceptable anti-proliferative effects against several cancer cell lines. Among them, CPUY074020 displayed potent dual G9a inhibitory activity and anti-proliferative activity. Furthermore, CPUY074020 induced cell apoptosis in a dose-dependent manner and displayed a significant decrease in dimethylation of H3K9. Simultaneously, CPUY074020 showed reasonable in vivo PK properties. Altogether, our workflow supplied a high efficient strategy in the identification of novel G9a inhibitors. Compounds reported here can serve as promising leads for further study.

Synthesis and bioactivity of novel isoxazole chalcone derivatives on tyrosinase and melanin synthesis in murine B16 cells for the treatment of vitiligo.

A new series of chalcone derivatives 1-18, bearing isoxazole moieties were designed and synthesized, and biologically evaluated for their activity on mushroom tyrosinase and melanin synthesis in murine B16 cells. The result indicated that most of prepared compounds 1-18 showed potent activating effect on tyrosinase, especially for 1-2, 4, 6-7, 9 and 15. Among them, compounds 2, 4 and 9 demonstrated the best activity with EC50=1.3, 2.5 and 3.0µmol·L-1 respectively, much better than the positive control 8-methoxypsoralan (8-MOP, EC50=14.8µmol·L-1); In B16 cells, all the tested compounds exhibited a stronger activity on melanogenesis than 8-MOP (with the value of 115%). It was interesting that derivatives substituted with halogen (1, 2, 4, 5, 7, 9) were generally more potent. Compounds 2 (463%) and 18 (438%) with 3 and 4-fold potency compared with 8-MOP respectively, were recognized as the most promising candidate hits for further pharmacological study of anti-vitiligo.