Research Journal of Chemical Sciences ________________________________________ ISSN 2231-606X  Vol. 1(5), 88-90, Aug. (2011) Res.J.Chem.Sci. International Science Congress Association  
88
 
Short CommunicationAntioxidant Potentialities of 4-Acyl isochroman-1,3-DionesDjandé Abdoulaye, Kiendrébéogo Martin, Compaoré Moussa, Kaboré Léopold,                                  
                      
Nacoulma G. Odile, Aycard Jean-Pierre and Saba Adama1* 1.Lab. de Chimie Bio-Organique et Phytochimie, UFR-SEA, Université de Ouagadougou, 03 BP 7021 Ouagadougou 03, Burkina FASO 2.Lab. de Biochimie and Chimie Appliquées, UFR-SVT, Université de Ouagadougou, 09 BP 848 Ouagadougou 09, Burkina FASO 3.Lab. de Spectrométries et Dynamique Moléculaire Université de Provence, Case 252, Centre de saint Jérôme, Avenue Escadrille Normandie, Niemen 13397, Marseille Cédex 20, FRANCE. Available online at: 
www.isca.in
(Received 09nd July 2011, revised 23rd July 2011, accepted 29th July 2011)Abstract A new family of compounds (4-acyl isochroman-1,3-diones), demonstrating antioxidant properties, have been synthesized and described. Their antioxidant properties are studied herein. These antioxidant characters increased with the electronic withdrawing character of the acyl substituent. So, 4-p-Cyanobenzoyl isochroman-1,3-dione and 4-p-Nitrobenzoyl isochroman-1,3-dione have been found to exhibit a reducing power and to scavenge the DPPH free radical using FRAP and DPPH assays..  Key words:Antioxidant activity, DPPH scavenging activity, Fe3+ reducing power, 4-acyl isochroman-1,3-diones, electro attracting character.IntroductionThe synthesis of 4-acyl isochroman-1,3-diones have been described for the first time in 1965 by J. Schnekenburger, followed in 1978 by R. N. Usgaonkar and al. Only three models of 4-acyl isochroman-1,3-diones had been obtained and described. Since a multitude of difficulties have been encountered in synthesizing 4-acyl isochroman-1,3-diones, no more investigations have been reported until 1996, when A. Saba evidenced best conditions for the preparation of these compounds. Then, some of these compounds have been synthesized in our laboratories according to scheme 1 to study their properties. 
O
O
O
RC
O
X
O
C
O
H
R
O
O
O
O
O
H
O
R
Homophtalic anhydride
4-acyl isochroman-1,3-dioneSolvent
Scheme 1 Reaction scheme for the formation of 4-acyl isochroman-1,3-dionesX = Cl or OCOR ; B = Pyridine or Triethylamine ;  Solvent = diethyl ether or THF 
: R = CH;  
: R = C;  
: R= C;  
:  R = -FC4 ;   
: R = -CHOC4 
: R =  -CNC4 : 
:  R = -NO. These compounds (
-7
) have been identified by their melting points (mp), IR, H, 13C + DEPT 135 and 17O NMR data3-5 and their structure studied by crystallography6-8. Recently, they have been found to be fluorescents. As the difficulties to obtain 4-acyl isochroman-1,3-diones have been overcome, we are now focusing on their chemical and biological potentialities. Enolic proton of 4-acyl isochroman-1,3-diones is susceptible to interfere with oxido- reduction. So these compounds could be antioxidants. Antioxidants have been widely used in different fields of industry and medicine as substances, which interrupt radical-chain oxidation processes, improve general health, help cell rejuvenation and prevent cancer. As a part of our continuing investigations about 4-acyl isochroman-1,3-diones, we report in this paper, for the very first time, their antioxidant potentialities, using in vitro evaluation models. Material and Methods Synthesis of 4-acyl isochroman-1,3-diones: 4-acyl isochroman-1,3-diones were synthesized as previously described and characterised3,5. The general scheme of synthesis is shown by figure 1. In brief, homophtalic anhydride and the selected R acid chloride (or R acid anhydride) with pyridine (when R is an aliphatic moiety), or triethylamine (for aromatic one) are stirred at room temperature in THF (or diethyl ether) for 2 to 3 hours to give the acylated compound in good yield. The crude product is recrystallized in dichloromethane or chloroform. When R is an aromatic moiety, it is necessary to reflux the mixture for 2 hours before purification. DPPH radical scavenging activity: DPPH radical scavenging activity was measured as described elsewhere11. Briefly, 1.5 mL of a freshly prepared DPPH solution (20 mg/mL in methanol) was added to 0.75 mL of 4-acyl isochroman-1,3-diones (1.562 – 100 µg/mL final concentrations). After shaking, the mixture was incubated for 15 min in darkness at room temperature and then absorbance was measured at 517 nm against a blank (without 4-acyl isochroman-1,3-dione). Inhibition 
Research Journal of Chemical Sciences _______________________________________________________ ISSN 2231-606X  Vol. 1(5), 88-90, Aug. (2011) Res.J.Chem.Sci. International Science Congress Association 
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percentage of free DPPH radicals (I %) was calculated following the formula: I (%) = (1 - A Sample/A Blank) x 100. blank and Asample are the absorbance of the blank and sample reactions. IC50 (Concentration inhibiting 50% of free DPPH radicals) was calculated from the plotting of inhibition percentage versus sample concentrations. Gallic acid (0.156 - 10 µg/mL) was used as positive control. Ferric-reducing power: The FRAP assay12 was used to evaluate the Fe(III) to Fe(II) reducing power. Briefly, 1 mL of sample (500µg/mL or 31.25 µg/mL in methanol) was mixed with 2.5 mL of phosphate buffer (0.2 mol, pH 6.6) and 2.5 mL of potassium hexacyanoferrate (1% in water). After 30 min incubation at 50 °C, 2.5 mL of trichloroacetic acid (10% in water) was added, and the mixture centrifuged at 3000 rpm for 10 min. The supernatant (2.5 mL) was mixed with water (2.5 mL) and 0.5 mL of FeCl(0.1 % in water), then absorbance was read at 700 nm against a calibration curve (100 - 1.562 µg/mL) of ascorbic acid. The reducing power was expressed as mg ascorbic acid equivalent g-1 of compound (mg AAE/g). Gallic acid (10 µg/mL) was used as positive control. Statistical analysis: Assays were run in triplicate and data given as mean value ± standard deviation. The software Graphpad Prism 5.03 for window was used to analyse the statistical significance of data by conducting Student’s tests and a  value  0.01 was considered as being significant.Results and DiscussionAntioxidant activity is a complex process that can occur through several mechanisms. Due to its complexity, more than one test must be carried out when evaluating the antioxidant activity of pure compounds or extracts10. Then, the antioxidant potentiality of 4-acyl isochroman-1,3-diones (scheme 1) was evaluated using both DPPH and FRAP essays. The DPPH test intends to measure the ability of antioxidant compounds to scavenge the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) by donation of hydrogen atom while the FRAP essay was used to estimate their Fe3+ to Fe2+ reducing power, resulting from their electron-donating capacity. Results are summarized in table 1.Table-1  Antioxidant activities of 4-acyl isochroman-1,3-diones Compounds DPPH
•
Scavenging Activity  IC(µg mL-1) Fe3+ Reducing Power (mmol AAE g-1) 
1
   R = CH
3
 n.a. 0.05 ± 0.01
 
a
 
2
  R = C
2
H
5
 na 0.01 ± 0.01
 
a
 
3
   R = C
6
H
5
 n.a. 0.01 ± 0.01
 
a
 
4
   R = -FC
6
H
4
 n.a. 0.05 ± 0.01
 
a
 
5
  R = -MeOC
6
H
4
 n.a. 0.05 ± 0.01
 
a
 
6
   R = -CNC
6
H
4
 9.00 ± 00
 
b
 0.58 ± 0.01
 
c
 
7
  R = -NO
2
C
6
H
4
 20.40 ± 0.50
 
a
 1.95 ± 0.03
 
d
 
Gallic acid
0.57 ± 0.01
 
c
 18.73 ± 0.21
 
e
 
Expressed as mean values ± SD of three replicates; n.a. Not active (IC50 � 100 µg/ml). In each column, data with different letters in superscript are statistically different by Student’s  tests (  value  0.01). Reducing power was given as mmol of Ascorbic Acid Equivalent/ g of 4-acyl isochroman-1,3-diones  (mmol AAE g-1). DPPH scavenging activity (IC50) was given as concentration (µg/mL) of 4-acyl isochroman-1,3-diones inhibiting/ scavenging 50% of free DPPH• radicals.The best antioxidant potentiality was recorded for the 4-Cyanobenzoyl-isochroman-1,3-dione 
 and 4-Nitrobenzoyl- isochroman-1,3-dione 
, 
 being the strongest DPPH radical scavenger (IC50 = 9.00 µg/ml) while 
 exhibit the best reducing power (1.95 mmole AAE -1). The compounds substituted with a methyl, ethyl, benzoyl, -Fluorobenzoyl or -Methoxybenzoyl group did not show any significant Fe3+ reducing nor DPPHscavenging activity. The difference observed in the antioxidant profile of 
, 
, 
, , , 
, and 
 could be related to the electro attracting character of substituted groups. The nitro (NO) and cyano (CN) functions in position para of the phenyl ring render the -Nitrobenzoyl and Cyanobenzoyl groups more electro attractant than the other groups. Consequently, the enolic proton of 
and 
 is comparatively, more available than those of 
, 
, 
, 
, and 
 for the oxido-reduction reaction conferring to both molecules 
 and 
, their antioxidant properties. Compared to gallic acid used as positive control, 
 and 
 demonstrate a weak to moderate antioxidant activities. However, taking in consideration our hypothesis, it might be possible to synthesize promising antioxidant 4-acyl isochroman-1,3-diones using more electro attracting acyl groups.    Conclusion Antioxidant potentialities of 4-acyl isochroman-1,3-diones 
 – 
) have been evaluated in this work. Compounds 
 and 
 have been found to be the most active in both DPPH and FRAP assays. The electro attracting character of the substituent R of these compounds was found to be responsible of the antioxidant activities. Hence, 4-acyl isochroman-1,3-diones with high electronic withdrawing character should be promising antioxidant compounds.  AcknowledgmentsWe are grateful to Pr. Thierry Chiavassa, Valerie Monnier and Laurence Carles from Université de Provence (France) for their contribution in the identification process of all the compounds. References1. Schnekenburger J., Acylderivate des Homophthalsäureanhydrids 2. Mitt. über Acylderivate methylenaktiver Dicarbonylverbindungen, Arch. Pharm., 298B 1, 4-18 (1965)
Research Journal of Chemical Sciences _______________________________________________________ ISSN 2231-606X  Vol. 1(5), 88-90, Aug. (2011) Res.J.Chem.Sci. International Science Congress Association 
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2. Nadkarni D.R. and Usgaonkar R.N., Convenient synthesis of natural occurring 3-propyl isocoumarin and 3-propyl-1(2H)-isoquinolone and other related compounds, Indian J. Chem.,16B, 320 (1978)3. Saba A., Recherche dans la série des sels de benzopyrylium Synthèse et étude de la structure des sels de 2-benzopyrylium Thèse d’Etat ès Sciences Physiques, Université de Ouagadougou 153 (1996)4.   Saba A., Sib S.F., Faure R. and Aycard J. P., NMR and AM1 study of the tautomeric equilibrium of isochroman-1,3-diones, Spectrosc. Let.,29(8), 1649-1657 (1996)  5.    Djandé A., Cissé L., Kaboré L., Saba A., Tine A. and Aycard J.P., Fluorescence properties of 4-acyl isochroman-1,3-diones, Heterocycl. Comm., 14(4), 237-245 (2008)6.  Kakou-Yao R., Saba A., Ebby N and Aycard J. P., Fluorescence properties of 4-acyl isochroman-1,3-diones, Z. Kristallogr., NCS214, 481-483 (1999)7.   Kakou-Yao R., Saba A., Ebby N., Pierrot M. and Aycard J.P., Tautomérie de la 4-(hydrophényl-méthylène) isochroman-1,3-dione à l’état, Acta Cryst., C55, 1591-1598 (1999)8.  Kakou-Yao R., Djandé A., Kaboré L, Saba A. and Aycard J.P., 4-[(1,3-dioxo isochroman-4-ylidene)-hydroxymethyl]benzonitrile, Acta Cryst.  E63, 4275 2007)9.Forest S.E., Stimson M.J. and Simon J.D., Mechanism for the photochemical production of superoxide by Quinacrine, J. Phys. Chem. B, 103(19) 396 (1999)10. Aruoma O.I., Methodological considerations for characterizing potential antioxidant actions of bioactive components in plant foods, Mutation Research 9(20), 523 (2003)11. Velasquez E., Tournier H.A., de Buschiazzo P.M., Saadevra G. and Schinella G.R., Antioxidant activity of Paraguayan plants extracts, Fitoterapia, 74(1/2) 91 2003)12. Hinneburg I., Dorman H.J.D and Hiltunen R., Antioxidant activities of extracts from  selected culinary herbs and spices, Food Chemistry,  97(1), 122-129 (2006)
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