Neuroprotective and Antioxidant Activities of 4-Methylcoumarins: Development of Structure–Activity Relationships

Abstract

Coumarins are a major class of polyphenols that are abundantly present in many dietary plants and possess different biological activities. Neuroprotective effect of 28 variously substituted 4-methylcoumarins was evaluated in a cell model of oxidative stress-induced neurodegeneration, which measures viability in PC12 cells challenged with hydrogen peroxide by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The inhibitory activity of these compounds against intracellular reactive oxygen species (ROS) formation was also determined by 2′,7′-dichlorofluorescein diacetate method in the same cells. Chemical redox-based assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) tests were employed to explore structure-antioxidant activity relationships in a cell-free environment. The results demonstrated that 4-methylcoumarins containing ortho-dihydroxy or ortho-diacetoxy substituents on the benzenoid ring possess considerable neuroprotective effects. ortho-Dihydroxy compounds inhibited cytotoxicity (44.7-62.9%) and ROS formation (41.6-71.1%) at 50 µM and showed considerable antioxidant effects. We conclude that 4-methylcoumarins are promising neuroprotective and antioxidant scaffolds potentially usefull for management of neurodegenerative diseases.Key words 4-methylcoumarin; neuroprotective; PC12 cell; neurodegenerative disease Coumarin derivatives containing benzopyran-2-one central core comprise a large class of plant-derived phenolic compounds that have diverse pharmacological effects and are considered as promising scaffolds for drug discovery. [1][2][3][4] Among these compounds, 4-methylcoumarins have demonstrated potential antioxidant activity with less toxicity compared to other coumarin derivatives.5,6) Antioxidant activities of various 4-methylcoumarin derivatives have been studied by our groups and other investigators 7-11) among which, 7,8-ortho-dihydroxy and 7,8-ortho-diacetoxy structures have shown promising effects in various test systems. 8,9,12,13) Since antioxidant agents may have great potential as neuroprotective compounds, in this study, we focused on the examination of the neuroprotective effect of previously synthesized 4-methylcoumarin derivatives in oxidative stress-induced neurotoxicity model in PC12 cells with a special focus on derivatives bearing 7,8-ortho-dihydroxy and 7,8-ortho-diacetoxy substitutions. MATERIALS AND METHODSChemicals RPMI1640, penicillin/streptomycin, sterile phosphate buffered saline (PBS) and trypsin ethylenediaminetetraacetic acid (EDTA) (0.25%) were purchased from Biosera (Ringmer, U.K.). Fetal bovine serum (FBS) and horse serum (HS) were acquired from Invitrogen (San Diego, CA, U.S.A.). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 2′,7′-dichlorofluorescein diacetate (DCFH-DA), hydrogen peroxide, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and N-acetyl-L-cysteine (NAC) were obtained from Sigma-Aldrich (San Louis, MO, U.S.A.). The rest of compounds were purchased from Merck (Darmstadt, Germ...

Discovery of novel dual-active 3-(4-(dimethylamino)phenyl)-7-aminoalcoxy-coumarin as potent and selective acetylcholinesterase inhibitor and antioxidant

“…The antioxidant evaluation of coumarin compounds showed that only 6a–c presented activity in Ferric Ion Reduction Method (FRAP) with values from 2.42 to 7.49 mmol Q/mol (Table 1). Series 4a–d and 5a–c did not demonstrate any considerable result, similar to other 7-alkoxy coumarins described in the literature 25 . Probably, the antioxidant effect is coming from dimethylamino-phenyl moiety and this feature could be explored in a forthcoming series.…”

“…e Antioxidant index based on quercetine (Q); FRAP value (mmol Q/mol). 7,8-dimethoxy-coumarin (NA) 25 and ethyl 2–(7,8-dimethoxy-2-oxo-2H-chromen-3-yl)acetate (1.2 ± 0.1) 25 .…”

Role of the p-Coumaroyl Moiety in the Antioxidant and Cytoprotective Effects of Flavonoid Glycosides: Comparison of Astragalin and Tiliroside

“…For example, apigenin-7- O -β- d -(6′′- p -coumaroyl)-glucopyranoside has been reported to exhibit neuroprotective effects in an experimental ischemic stroke mode [ 8 ], whereas tiliroside has been reported to inhibit neuroinflammation [ 9 ] and acute inflammation [ 10 ]. Notably, all of these effects have been attributed to the antioxidant activity of these compounds [ 10 , 11 , 12 ]. However, the role of the p -coumaroyl moiety found in these flavonoid glycoside compounds in their antioxidant activity remains unknown, despite numerous studies towards the structure–activity relationships of flavonoids and flavonols [ 13 , 14 , 15 ].…”

Antioxidant Effects of Oleuropein on Hydrogen Peroxide-Induced Neuronal Stress- An In Vitro Study

“…Sun et al ., [ 20 ] documented that the application of H 2 O 2 (100µM) caused significant cell loss in in vitro neuroblastoma culture. This data is in agreement with those of Malhotra et al ., [ 21 ] who reported that 1h incubation of H 2 O 2 caused significant cell losses on viability. In previous researches [ 22 - 24 ], it has been reported that H 2 O 2 caused cell losses by increasing ROS production, pro-apoptotic Bax protein levels and DNA fragmentation.…”