A Triterpene from Rosa sp.

Transcription

1 JRSCE Vol. 4 No. 2 August 2007 De La Salle University-Manila A Triterpene from Rosa sp. Consolacion Y.. Ragasa,*, Agnes B. Alimboyougen, and John A.. Rideout 2 Chemistry Department, De La Salle University-Manila 2 School of Chemical and Biomedical Sciences, Central Queensland University The dichloromethane extract of red rose petals afforded 2-oxopomolic acid () and sitosterol by silica gel chromatography. The structure of was elucidated by extensive D and 2D NMR spectroscopy. Antimicrobial tests on indicated that it is active against the fungi C. albicans and T. mentagrophytes. It was also found to be slightly active against the bacteria E. coli, P. aeruginosa, and S. aureus. It was inactive against B. subtilis and A. niger. Keywords: Rosa sp., Rosaceae, 2-oxopomolic acid. INTRDUCTIN Red rose is an ornamental plant commonly found in flower shops throughout Metro Manila. The large variety of red roses is usually grown in the Mountain Province where the cool climate is conducive for its growth. Literature search revealed that several studies have been conducted on the chemical constituents of the genus Rosa. Rosa multiflora which afforded fupenzic acid, 2-oxo-pomolic acid, euscaphic acid, 2α, 3α, 9α, 24-tetrahydroxyolean-2-en-28-oic acid, kaji-ichigoside F, rosamultin, and nigaichigoside F2 (Li, et al., 2002). Pomolic acid, isolated from R.woodsii and.capitata, was identified as an anti-iv agent (EC50.4µg/mL, T.I. 6.6) (Neto, et al., 2000). A 2-xopomolic acid indicated radical scavenging activities similar to α- tocopherol (D Abrosca, et al., 2005). The study reports the isolation and structure elucidation by D and 2D NMR spectroscopy of 2- oxopomolic acid () and sitosterol from red rose petals RESULTS AND DISCUSSIN C 4 28 The dichloromethane extract of the air-dried red rose petals afforded and sitosterol by silica gel chromatography. The structure of was elucidated by extensive D and 2D NMR spectroscopy as follows. The 3 C NMR spectral data of (Table ) gave resonances for thirty carbons with the following 27 * Corresponding author: ragasac@dlsu.edu.ph

2 2 JURNAL F RESEARC IN SCIENCE, CMPUTING, AND ENGINEERING VL. 4 N. 2 Table 400 Mz NMR and 00Mz 3 C NMR, MBC and NESY correlations of Position δ C δ * mult. (J z) MBC Correlations NESY Correlations (9.3), 2.2 (9.3) , (s) -, -5, , , -6, -7, , , , (br s) -8-8, , , , , 3-29, , , (Me, s) (Me, s) -3, (Me, s) 3-23, (Me, s) (Me, s) (Me, s) (Me, d, 6.4) -2, 3-29 * multiplet, unless otherwise indicated. functionalities: a carbonyl of a ketone at δ 2.0, two carbinyl carbons at δ 82.9 and 73., and olefinic carbons at δ 28.4 and The rest of the resonances belong to methyl, methine, and methylene carbons. This suggested a triterpene with the functionalities of a ketone, an olefin, and two alcoholic groups. The NMR spectral data of (Table ) indicated an olefinic proton at δ 5.35, a carbinyl proton at δ 3.9, six methyl singlets at δ 0.69, 0.74, 0.88,.9,.2, and.32, and a methyl doublet at The geminal protons at δ 2.47 and 2.2 were assigned a to the carbonyl. The CSY spectrum of gave four isolated spin systems, which is as follows: -5/ 2-6/ 2-7; -9/ 2 -/-2; 2-5/ 2-6; -20/ 2-2/ 2-22 (Figure ).

3 A TRITERPENE FRM RSA SP. RAGASA, C., ALIMBYUGEN, A. & RIDEUT, J. 3 : CSY C : MBC Figure - CSY and Key - 3 C Long-Range Correlations for The and 3 C assignments of (Table ) were verified by SQC and connectivity was verified by MBC (Table and Figure ). The carbonyl was assigned to position 2, one of the carbinyl carbons was placed in position 3, and the α-methylene protons were in position due to the long-range correlations between the carbonyl carbon at δ 2.0 (C-2), the methylene protons at δ 2.47 and 2. ( 2 -), and the carbinyl proton at δ 3.9 (-3). The carboxylic acid was placed at position 28 on the basis of a longrange correlation between the carbonyl carbon at δ 83.0 (C-28) and the methine proton at δ 2.56 (- 8). This proton was, in turn, correlated long-range to the olefinic carbons at δ 38.2 (C-3) and 28.4 (C-2). Thus, the double bond was placed at C-2 and C-3. The second carbinyl was placed at C-9 due to the long-range correlation between the proton at δ 2.56 (-8) and the carbinyl carbon at δ 73. (C-9). All long-range correlations observed were consistent with the structure of. The relative stereochemistry was deduced by NESY as follows. The carbinyl proton at δ 3.9 (-3) was close in space to the methyl protons at δ 0.69 ( 3-23) and the methine proton at δ.45 (-5) which was, in turn, close to the proton at δ.95 (-9), to which this was close to the methyl singlet at δ.32 ( 3-27). The methyl singlets at δ.9 ( 3-24), 0.88 ( 3-25), and 0.74 ( 3-26) were close to each other on the opposite face of. The methyl singlet at δ.2 ( 3-29) was close to the methyl singlet at δ 0.95 ( 3 ), the methine proton at δ 2.56 (-8), and the olefinic proton at δ 5.35 (-2), indicating that they were close to each other in space. C Fig. 2. Key NESY correlations for Figure 2 Key NESY Correlations for

4 4 JURNAL F RESEARC IN SCIENCE, CMPUTING, AND ENGINEERING VL. 4 N. 2 Literature search revealed that is 2- oxopomolic acid. The 3 C NMR spectral data of and 2-oxopomolic acid β-d-glucopyranosyl ester (Zhong-Jian, et al., 993) were similar, except in the region where differences occur, e.g., glucose esterified to the carboxylic acid. As part of our continuing search for possible antimicrobial compounds from Philippine medicinal plants, was tested for its antimicrobial potential against seven microorganisms. Results of the study (Table 2) indicated that is active against the fungi C. albicans and T. mentagrophytes, with an activity index of 0.3 and 0.2, respectively, at a concentration of 30 µg. It was also found to be slightly active against the bacteria E. coli, P. aeruginosa, and S. aureus, with an activity index of 0., 0.2, and 0., respectively, at the same concentration. It was inactive against B. subtilis and A. niger. Table 2 Antimicrobial Test Results on rganism Sample(30 µg) Clearing Zone (mm) Antimicrobial Replicate Replicate2 Replicate3 Index (AI) E. coli 0. Chloramphenicol P. aeruginosa Chloramphenicol 4.3 S. aureus 0. Chloramphenicol B. subtilis Chloramphenicol C. albicans Canesten, 0.2 g a T. mentagrophytes Canesten, 0.2 g a A. niger Canesten, 0.2 g a 23.3 a Contains % chlotrimazole. 2. General Experimental Procedures NMR spectra were recorded on a Bruker Avance 400 in CDCl 3 at 400 Mz. for and 00 Mz for 3 C. Column chromatography was performed with silica gel 60 ( mesh), while the TLC was performed with plasticbacked plates coated with silica gel F 254. The plates were visualized with vanillin- 2 S 4 and warming. (?) 2.2 Sample Collection Flowers of red roses were obtained from a flower shop in Cubao, Quezon City in February. It was identified as Rosa sp. at the Philippine National Museum and a voucher specimen, PN No , was deposited at the Philippine National Museum. owever, since the commercial red roses may be a cross breed of several varieties of roses, the species could not be identified.

5 A TRITERPENE FRM RSA SP. RAGASA, C., ALIMBYUGEN, A. & RIDEUT, J Isolation ACKNWLEDGMENT The air-dried flowers (.2 kg) of Rosa sp. were ground in an osterizer, soaked in dichloromethane for three days, then filtered. The filtrate was concentrated under a vacuum to afford a crude extract (50 g) which was chromatographed in increasing proportions of acetone in dichloromethane at 0% increments. The dichloromethane and 0% acetone in dichloromethane fractions were rechromatographed (thrice) in 5% ethyl acetate in petroleum ether to afford sitosterol (20 mg). The 60-70% acetone in dichloromethane fractions were rechromatographed (five times) in diethyl ether:acetonitrile: dichloromethane (.5:.5:7) to afford (5 mg). 2.4 Antimicrobial Tests The microorganisms used were obtained from the University of the Philippines Culture Collection (UPCC). These were Pseudomonas aeruginosa (UPCC 244), Bacillus subtilis (UPCC 49), Escherichia coli (UPCC 95), Staphylococcus aureus (UPCC 43), Candida albicans (UPCC 268), Trichophyton mentagrophytes (UPCC 493) and Aspergillus niger (UPCC 370). Compound was dissolved in 95% ethanol. The antimicrobial assay reported in the literature was employed [5]. The antimicrobial tests were conducted at the University of the Philippines-Natural Sciences Research Institute (UP-NSRI). Research grants from the Science Foundation and the University Research Coordination ffice of the De la Salle University are gratefully acknowledged. REFERENCES D Abrosca, B., Fiorentino, A., Monaco, P., & Pacifico, S. (2005). Radical-scavenging activities of new hydroxylated ursane triterpenes from cv. cnnurca apples. Chemistry and Biodiversity, 2(7), Guevara, B. Q. & Recio, B.V. (985). Acta Manilana Supplements. Manila: UST Research Center. Li, Yanfang; Lihong u, & Fengchang, Lou. (2002). Studies on the constituents of Rosa multiflora Thunb. Zhongguo Yaoke Daxue Xuebao, 33(3), Neto, C.C., Vaisberg, A. J., Zhou, B.N., Kingston, D.G.I., & ammond, G.B. (2000). Cytotoxic triterpene acids from the Peruvian medicinal plant polylepis racemosa. Planta Medica. 66(5), Zhong-Jian, J., Xiang-Quian, L., & Zi-Min, L. (993). (title). Phytochemistry, 32(),