This Issue is Dedicated to the Memory of Professor Ivano Morelli

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1088 Natural Product Communications Vol. 1 (12) 2006 Speranza et al. kenyaloside (1, 50 mg) in H 2 O (25 mL), and the mixture was incubated at 37° for 3 h under nitrogen. After adding MeOH, the solution was filtered and concentrated under reduced pressure. Column chromatography of the aqueous residue (eluent: EtOAc-EtOH-H 2 O, 100:20:13) gave two fractions. The less polar fraction, after further purification by column chromatography eluting with AcOEt-EtOH (from 5:1 to 1:1), furnished the diglycoside 2 (30 mg, 79%) as a pale yellow powder. The more polar fraction was submitted to column chromatography (eluent AcOEt-EtOH, from 3:1 to 1:1) to give glucose (9 mg, 67%), identified by TLC comparison with an authentic sample (eluent B, Rf 0.31). Compound 2 (20 mg), dissolved in 50 mM phosphate buffer pH 6 (5 mL), was incubated with α-rhamnosidase from Fusarium oxyporum CCF 906 (0.2 U) [11] at 35°C for 24 h. After concentration, MeOH was added, the precipitate removed by filtration and the solvent evaporated under reduced pressure. Repeated column chromatographic purification (eluent AcOEt-EtOH, from 5:1 to 1:1 and from 3:1 to 1:1) furnished rhamnose (5 mg, Rf 0.62, eluent B, co-TLC with an authentic sample) and a yellow product (10 mg, Rf 0.73, eluent A). This was hydrolyzed without further purification (0.1 N HCl, dioxane-H 2 O, 1:1, 5 mL; 70°C, 5 h, under nitrogen) to give xylose (Rf 0.50, eluent B, co-TLC with an authentic sample), which was purified (1.5 mg) by column chromatography (eluent AcOEt- EtOH, from 3:1 to 1:1). 8-(α-L-Rhamnopyranosyloxy)-3-(β-Dxylopyranosyloxymethyl)naphthalen-ol (2) [α] D : - 36.2º (c 0.07, MeOH). Rf : 0.54(AcOEt-EtOH-H 2 O, 100:20:13). IR (KBr): 1635 cm -1 . UV/Vis λ max (MeOH) nm (log ε): 225 (4.49), 258sh (4.09), 297 (3.99), 334 (3.80). 1 H NMR (400 MHz, CD 3 OD): Table 1. 13 C NMR (100 MHz, CD 3 OD): Table 1. ESI MS: m/z 533 [M + Na + ], 387 [M-146+Na + ]. Determination of the absolute configuration of the isolated sugars: The isolated monosaccharides were converted into methyl glycopyranosides followed by treatment with excess p-bromobenzoyl chloride, as in ref. 9. Comparison of the CD spectra of the resulting per-p-bromobenzoates with those of the analogous derivatives prepared from authentic samples allowed the D-configuration for glucose and xylose and the L- configuration for rhamnose to be established. Acknowledgments – Thanks are due to Dr Lavinia Durì for technical assistance and to MIUR for financial support. References [1] Speranza G, Morelli CF, Tubaro A, Altinier G, Durì L, Manitto P. (2005) Aloeresin I, an anti-inflammatory 5-methylchromone from Cape aloe. Planta Medica, 71, 79-81. [2] Trease GE, Evans WC. (1983) Pharmacognosy, Baillière Tindall, London, 404-408. [3] Durì L, Morelli CF, Crippa S, Speranza G. (2004) 6-Phenylpyrones and 5-methylchromones from Kenya aloe. Fitoterapia, 75, 520-522. [4] Reynolds T. (2004) Aloe chemistry. In Aloes. The genus Aloe. Reynolds T (Ed). CRC Press, Boca Raton, USA. 39-74. [5] Dagne E, Bisrat D, Viljoen A, Van Wyk B-E. (2000) Chemistry of Aloe species. Current Organic Chemistry, 4, 1055-1078. [6] Batterham T, Cooke RG, Duewell H, Sparrow LG. (1961) Colouring matters of Australian plants. VIII. Naphthalene derivatives from Dianella species. Australian Journal of Chemistry, 14, 637-642. [7] Speranza G, Corti S, Manitto P. (1994) Isolation and chemical characterization of a new constituent of Cape aloe having the 1,1-diphenylethane skeleton. Journal of Agricultural and Food Chemistry, 42, 2002-2006. [8] (a) Buckingham J. (2005) Dictionary of Natural Products on CD-ROM. Chapman & Hall/CRC, England; (b) Editorial (1997) Planta Medica, 63, 195. [9] Golik J, Liu H-W, Dinovi M, Furukawa J, Nakanishi K. (1983) Characterization of methyl glycosides at the pico- to nano-gram level. Carbohydrate Research, 118, 135-146. [10] Nakanishi K, Kuroyanagi M, Nambu H, Oltz EM, Takeda R, Verdine GL, Zask A. (1984) Recent application of circular dichroism to structural problems, especially oligosaccharide structures. Pure and Applied Chemistry, 56, 1031-1048. [11] Monti D, Pišvejcová A, Křen V, Lama M, Riva S. (2004) Generation of an α-L-rhamnosidase library and its application for the selective derhamnosylation of natural products. Biotechnology and Bioengineering, 87, 763-771. [12] Pham TN, Hinchley SL, Rankin DWH, Liptaj T, Uhrínpp D. (2004) Determination of sugar structures in solution from residual dipolar coupling constants: methodology and application to methyl β-D-xylopyranoside. Journal of the American Chemical Society, 126, 13100-13110.
NPC Natural Product Communications New Flavonoid Glycosides from Chrozophora senegalensis and Their Antioxidant Activity 2006 Vol. 1 No. 12 1089 - 1095 Antonio Vassallo a , Giuseppina Cioffi a , Francesco De Simone a , Alessandra Braca b , Rokia Sanogo c , Angelo Vanella d , Alessandra Russo d and Nunziatina De Tommasi a* a Dipartimento di Scienze Farmaceutiche, Università di Salerno, Via Ponte Don Melillo, 84084 Fisciano, Salerno, Italy b Dipartimento di Chimica Bioorganica e Biofarmacia, Università di Pisa, Via Bonanno 33, 56126 Pisa, Italy c Departement Medicine Traditionelle (DMT), INRSP, B.P. 1746, Bamako, Mali d Dipartimento di Chimica Biologica, Chimica Medica e Biologia Molecolare, Università di Catania, v.le A. Doria 6, 95125 Catania, Italy detommasi@unisa.it Received: June 27 th , 2006; Accepted: September 27 th , 2006 Dedicated to the memory of Professor Ivano Morelli. Bioassay-directed fractionation of an antioxidant methanol extract of the leaves of Chrozophora senegalensis using DPPH assay led to the isolation of three new flavonoid glycosides, quercetin 3-O-(6''-caffeoyl)-β-D-glucopyranoside-3'-O-β-Dglucopyranoside (1), quercetin 3-methyl ether-7-O-α-L-rhamnopyranosyl-(1→6)-(2''-p-coumaroyl)-β-D-glucopyranoside (2), acacetin 7-O-(6''-p-coumaroyl)-β-D-glucopyranoside (3), along with five known flavonoids, one phenolic derivative, and three megastigmane glycosides. Their structures were established on the basis of detailed spectral analysis. All isolated compounds were tested for their antioxidant activity on DPPH stable radical, superoxide anion, metal chelating activity, and DNA cleavage induced by the photolysis of H 2 O 2 . Quercetin 3-O-(6''-caffeoyl)-β-D-glucopyranoside-3'-O-β-D-glucopyranoside (1), quercetin 3'-methyl ether-3-O-α-L-rhamnopyranoside (4), and 4'''-methyl ether amenthoflavone (9) exhibited the highest antioxidant capacity being also able to modulate hydroxyl radical formation more efficiently than other compounds acting as direct hydroxyl radical scavengers and chelating iron. Keywords: Chrozophora senegalensis, Euphorbiaceae, flavonoids, antioxidant activity. In recent years, a global trend toward the use of natural phytochemicals present in herbs and functional foods as antioxidants was further increased after that it had been reported that some commonly used synthetic antioxidant compounds, such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole, have long-term toxicological effects, including carcinogenicity [1]. Of particular interest as possible sources of natural antioxidants are medicinal plants traditionally used to treat conditions related to oxidative stress, such as rheumatism and inflammation. In this regard, many phytochemicals with diversified biological properties have shown promise for the prevention and/or treatment of all diseases in which oxidative stress plays a key role [2]. Chrozophora senegalensis (Lam) A Juss. ex Spreng, syn. Croton senegalensis (Euphorbiaceae family) is a small tree widely distributed in Mali where it grows wild and is used in folk medicine for the treatment of diarrhea, rheumatism, teniasis, stomachache, rachitis, and venereal diseases. The leaf and root decoctions are also drunk for hairloss [3, 4]. To confirm the use of C. senegalensis in Malian traditional medicine, the extracts of the leaves were evaluated for in vitro antioxidant activity. A bioassay-guided fractionation procedure showed that
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