Antioxidant compounds from Ebenus pinnata

Fitoterapia 78 (2007) 32–34www.elsevier.com/locate/fitoteShort reportAntioxidant compounds from Ebenus pinnataPedro M. Abreu a, ⁎ , Hatem Braham b , Hichem Ben Jannet b ,Zine Mighri b , Susan Matthew aa REQUIMTE, Departamento de Química, FCT-UNL, 2829-516 Caparica, Portugalb Laboratoire de Chimie des Substances Naturelles et de Synthèse Organique 99/UR/12-26,Faculté des Sciences de Monastir, 5000 Monastir, TunisiaReceived 13 July 2005; accepted 4 September 2006Available online 23 September 2006AbstractActivity-guided fractionation of the methanol extract of Ebenus pinnata aerial parts led to the isolation of ombuoside (1),kaempferol 3-O-rutinoside (2), rutin (3), catechin (4), and picein (5), along with β-sitosterol and β-sitosterol glucoside.Compounds 1–4 showed significant antioxidant activity in the DPPH, and TEAC, reducing power assays.© 2006 Elsevier B.V. All rights reserved.Keywords: Ebenus pinnata; Flavonoids; Antioxidant activity1. PlantEbenus pinnata Ait. (Leguminosae), aerial parts collected at Chott Mériem Sousse (Tunisia), in May 1999 wereauthenticated by Dr. F. Harzallah-Skhiri. A voucher specimen has been deposited in the Ecole Supérieured'Horticulture et d'Elevage de Chott Mériem, Université de Sousse, Tunisie.2. Uses in traditional medicineNo reports.3. Previously isolated compoundsNo reports.4. New isolated compoundsOmbuoside (quercetin-4′,7-dimethoxy-3-O-rutinoside) (1) [1], kaempferol-3-O-rutinoside (2) [2], rutin (3) [3],catechin (4) [4], picein (4-O-β-D-glucopyranosyl acetophenone) (5) [5], β-sitosterol, and β-sitosterol glucoside.⁎ Corresponding author. Fax: +351 212948550.E-mail address: pma@dq.fct.unl.pt (P.M. Abreu).0367-326X/$ - see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.fitote.2006.09.013

P.M. Abreu et al. / Fitoterapia 78 (2007) 32–34335. Studied activityAntioxidant activity evaluated using three different assays [6]: DPPH (2,2-diphenylpicryl hydrazyl) scavengingactivity [7], ABTS U+ scavenging activity according to the modified TEAC method of Re et al. [8], and reducing powerassay according to the method of Oyaizu [9].6. Tested materialMethanol extract of E. pinnata aerial parts, CHCl 3 and EtOAc fractions obtained from partition with a suspension ofthe MeOH extract in water, and compounds 1–4.7. ResultsReported in Table 1.8. ConclusionsThese results are in agreement with reported structure–activity relationships for flavonoid antioxidants, whosescavenging effects depend on the hydroxylation pattern of rings A, B, and C, O-methylation, the presence of a 2,3double bond in conjugation with a 4-oxo function, glycosylation, and degree of polymerization [10–13]. As expected,

34 P.M. Abreu et al. / Fitoterapia 78 (2007) 32–34Table 1Antioxidant activity of compounds 1–4, MeOH extract, CHCl 3 and AcOEt fractions from E. pinnataMaterial DPPH radical (μg/ml) ABTS TEAC (mM) a Reducing power IC 50 (μg/ml)1 49.05 ±5.88 0.87 ±0.08 193.72 ±4.52 37.77 ±1.47 1.59 ±0.04 108.77 ±5.33 16.15 ±0.27 2.50 ±0.05 40.06 ±1.84 9.24 ±0.12 2.11 ±0.06 29.58 ±0.8MeOH extract N1000 – 0.83 ±0.16 844.7 ±7.9CHCl 3 fractionb– 0.61 ±0.16 1081.0 ±12.5EtOAc fraction 637.61 ±7.96 1.55 ±0.12 740.0 ±8.6Quercetinc– 4.00 ±0.12 21.9 ±0.3Tocopherolc–c136.83 ±0.2a TEAC values were calculated at 15 min.b No activity observed.c Not determined.compounds bearing the orthodiphenolic structure in the B ring (3 and 4) are more active than the O-methylatedderivative 1, and the 4′-hydroxylated compound 2. Regarding the significance of Δ 2 and a 4-carbonyl group for theantioxidant activity, no consistent correlation could be identified from previous systematic studies of flavonoids[10,12]. For example, catechin (4) lacks the unsaturated system in ring B but showed the highest activity in the DPPHassay. When compared to quercetin, compound 3 shows less activity due to the glycosylation at C-3. The results herepresented indicate that flavonoids constitute the antioxidant principles of E. pinnata.AcknowledgmentsFoundation for Science and Technology, Portugal, for a post-doc grant (S. Matthew, SFRH/BPD/8570/2002), andGRICES for financial support (H. Braham).References[1] Inigo RPA, Pomilio AB. Phytochemistry 1985;24:347.[2] Chaurasia N, Wichtl M. Planta Med 1987;432.[3] Markham KR, Ternai B. Tetrahedron 1976;32:2607.[4] Sang S, Lapsley K, Rosen R, Ho CT. J Agric Food Chem 2002;50:607.[5] Ushiyama M, Furuya T. Phytochemistry 1989;28:3009.[6] Braham H, Mighri Z, Ben Jannet H, Matthew S, Abreu PM. J Nat Prod 2005;68:517.[7] Blois MS. Nature 1958;181:1199.[8] Re R, Pellegrini N, Proteggente A, Pannala A, Yang M, Rice-Evans C. Free Radic Biol Med 1999;26:1231.[9] Oyaizu M. Jpn J Nutr 1986;44:307.[10] Heim KE, Tagliaferro AR, Bobilya DJ. J Nutr Biochem 2002;13:572.[11] Bors W, Heller W, Michel C, Saran M. Methods Enzymol 1990;186:343.[12] Burda S, Oleszek W. J Agric Food Chem 2001;49:2774.[13] Rice-Evans C, Miller NJ, Paganga G. Free Radic Biol Med 1996;20:933.