s Chemis ct try u d & o r R P e s l e Powder-George, Nat Prod Chem Res 2017, 5:5 a r a r u t c h a DOI: 10.4172/2329-6836.1000274 N Natural Products Chemistry & Research ISSN: 2329-6836 Research Article Open Access Luteolin-7-O-Glycosides from the Leaves of Centropogon cornutus (Campanulaceae) Powder-George YL* Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago Abstract A new luteolin-7-O-glycoside, named Centropogin A (1), together with three known luteolin-7-O-glycosides, Luteolin- 7-O-xyloside (2), Luteolin-7-O-[β-apiofuranosyl-(1→2)]β-xylopyranoside (3) and Luteolin-7-O-[β-glucopyranosyl- (1→2)-α-rhamnosyl-(1→6)] β-glucopyranoside (4) were isolated and purified via repeated chromatography of the n-BuOH soluble fraction from the methanol extract of the leaves of Centropogon cornutus (Campanulacae). The structures of these compounds were elucidated by analysis of their 1D-NMR (1H, 13C) and 2D-NMR (COSY, HSQC, HMBC), MS (HR-ESIMS) spectral data, and by comparisons with the literature data. This is the first report of secondary metabolites from the genus Centropogon and the first report of compounds (2)-(4) from the Campanulaceae family. Keywords: Campanulaceae; Centropogon cornutus; Flavonoids; Experimental Section Luteolin-7-O-glycosides; Centropogin A; NMR; HR-ESIMS General experimental procedures Introduction NMR spectra were recorded on a Bruker AVANCE DRX-600 Campanulaceae, the bellflower family, is a well-known group of instrument with TMS as internal standard. HRESIMS was carried plants comprising 84 genera and approximately 2400 species [1]. The out on a micrOTOF-Q (Bruker Daltonics) spectrometer. Column family is cosmopolitan in its distribution and present in a wide array chromatography (CC) was performed on Silica gel 60 Å 70-230 mesh of habitats [2]. A few species in the family belonging to the genera (Sigma-Aldrich) and VLC was performed using Silica gel 60 PF254+366 Adenophora, Codonopsis, Lobelia and Platycodon have previously been (Merck). Analytical TLC was carried out on aluminium-backed analyzed with respect to their secondary metabolites and biological plates precoated with 0.20 mm thick silica gel (Sigma-Aldrich) and activities, and a diverse range of compounds have been isolated to date. visualization of the chromoplates was facilitated by UV light. The These include pyrrolidine, piperidine and polyhydroxylated alkaloids, solvents used for extraction and chromatographic separations were steroidal saponins, triterpenoids, phenylpropanoids, flavonoids, either of analytical grade or distilled prior to use. xanthones, polyacetylenes and cerebrosides, some of which exhibited significant anticancer, antimicrobial and anti-inflammatory activities Plant material [3-8]. Centropogon, the third largest genus of Campanulaceae, comprises The leaves of Centropogon cornutus investigated in this study of 230 species [9]. Centropogon cornutus is the only Centropogon were collected on the Guaico Tamana road, Trinidad in August 2013. species found in Trinidad and Tobago, where it is commonly known Identification and botanical authentication was performed by Ms. as deer meat, deer bush and crepe coq [10]. These showy roadside Keisha Manuare of the National Herbarium of Trinidad and Tobago plants, generally found along moist shady banks and cocoa fields, are and a voucher specimen (TRIN 50133) was deposited. distributed throughout Central and South America and the West Indies [10]. Centropogon cornutus is a shrub with a milky sap that grows to Extraction and isolation about 1-3 meters in height. It has curved scarlet flowers, which are suited for pollination by hummingbirds, and produces berries which The leaves of Centropogon cornutus were oven-dried for 3 days are consumed by birds [11]. Traditionally, the leaves are used to treat at 40°C (473 g), pulverized and extracted exhaustively with MeOH. snake and scorpion bites in Trinidad [12]. In Guyana, the entire plant The methanolic solution was filtered and concentrated in vacuo to is boiled and the liquid drank to remedy venereal diseases. In French yield 159 g of a viscous, dark-brown extract which was suspended in Guiana, the leaves are used as a tonic and as an abortive decoction, MeOH/H2O (4:1) and partitioned sequentially with Petroleum ether, while in NW Guyana it is used to treat urinary tract problems [13]. The CHCl3, EtOAc and n-BuOH, respectively. The n-BuOH extract (22 g) whole plant is also traditionally used to treat stomach ulcers in Brazil was subjected to vacuum liquid chromatography (VLC) on silica gel [14]. Many chemical and pharmacological investigations focusing (Silica gel 60 PF254+366) and eluted with EtOAc: MeOH: H2O gradients on a few genera of Campanulaceae have been carried out previously, of increasing polarity (95:3:2, 90:6:4, 80:12:8) to give 9 fractions (1A– however, there is limited information on the pharmacological or 1I). Fraction 1B, a pure compound was assigned as compound 2 (22.1 phytochemical composition of the Centropogon genus which has until mg). Fraction 1E (0.9227 g) was purified by isocratic silica gel column now not been investigated for its natural products. As a continuation of the search for secondary metabolites of biological importance from Campanulaceae species, herein, the isolation and structural elucidation *Corresponding author: Yomica L Powder-George, Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago, Tel: of one new compound and three known compounds from the n-BuOH +18686626013; Fax: +18686453771; E-mail: [email protected] soluble fraction from the methanol extract of the leaves of C. cornutus is reported. Their structures were elucidated using spectroscopic Received July 11, 2017; Accepted July 28, 2017; Published August 08, 2017 methods including NMR and HR-ESIMS as the novel Centropogin Citation: Powder-George YL (2017) Luteolin-7-O-Glycosides from the Leaves A (1), together with three known luteolin glycosides, Luteolin-7-O- of Centropogon cornutus (Campanulaceae). Nat Prod Chem Res 5: 271. doi: xyloside (2), Luteolin-7-O-[β-apiofuranosyl-(1→2)]β-xylopyranoside 10.4172/2329-6836.1000274 (3) and Luteolin-7-O-[β-glucopyranosyl-(1→2)-α-rhamnosyl-(1→6)] Copyright: © 2017 Powder-George YL. This is an open-access article distributed β-glucopyranoside (4) which are all for the first time reported from the under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the Campanulaceae family (Figure 1). original author and source are credited. Nat Prod Chem Res, an open access journal Volume 5 • Issue 5 • 1000271 ISSN: 2329-6836 Citation: Powder-George YL (2017) Luteolin-7-O-Glycosides from the Leaves of Centropogon cornutus (Campanulaceae). Nat Prod Chem Res 5: 274. doi: 10.4172/2329-6836.1000274 Page 2 of 4 OH OH H 3' OH 2' 4' H 3' OH H 2' H 4' 4" 5" O 1 B 8 1' 5" O 1 B HO O O 8 1' 7 9 2 5' HO O O HO 1" H 7 9 2 5' 3" 6' HO 1" H A 3" 6' O C A C OH H 3 H OH 6''' 6 10 H 3 H 4 6 10 4 H 5 H H H 4''' O 5 HO 5''' HO 1''' OH O OH O 3''' 2''' OH 2 H 1 OH HO OH 3' H OH HO 3''' 2' 4' 2'''' H H3C 6'''' O B 5'''' 4" 5" O 1 1'''' O 8 O 1' OH HO 7 9 2 5' HO 1" H O 3" 6' H 3' OH A 2' O C 6'' 4' H 3 H H 6 10 4 4" B H H 5" O 1 5 O 8 O 1' O HO 7 9 2 5' HO H 4''' 2" 1" 6' 1''' OH O OH 3''' A C H 3 H 2''' 6''' 6 10 4 HO O H 5 H 4"' 5''' OH 5"' O HO HO OH O HO 3"' 1"' 3 OH H 4 Figure 1: Structures of Centropogin A (1), Luteolin-7-O-xyloside (2), Luteolin-7-O-[β-apiofuranosyl-(1→2)]β-xylopyranoside (3) and Luteolin-7-O-[β-glucopyranosyl- (1→2)-α-rhamnosyl-(1→6)] β-glucopyranoside (4). 1 chromatography using the system EtOAc: MeOH: H2O (90:6:4) to C25H25O14, 549.1239); H-NMR (DMSO-d6, 600 MHz) δ: 12.99 (1H, yield compound 3 (155.9 mg). 1G (0.5025 g) was subjected to isocratic bs, OH-5), 7.46 (1H, dd, J=8.0, 2.0, H-6′), 7.44 (1H, d, J=2.0, H-2′), silica column chromatography using the system EtOAc: MeOH: H2O 6.91 (1H, d, J=8.0 Hz, H-5′), 6.76 (1H, d, J=2.0, H-8), 6.75 (1H, s, H-3), (90:6:4) to afford compound 1 (12.4 mg) and Fraction 1I (10.124 g) was 6.39 (1H, d, J=2.0, H-6), 5.19 (1H, d, J=7.6 Hz, Xyl-H-1), 5.34 (1H, bs, chromatographed on a gradient elution silica column chromatography Api-H-1); 13C-NMR (DMSO-d , 150 MHz) δ: 164.5 (C-2), 103.1 (C- using the mobile phase CHCl : MeOH (75:25, 65:35) to give compound 6 3 3), 181.9 (C-4), 161.2 (C-5), 99.3 (C-6), 162.4 (C-7), 94.5 (C-8), 156.9 4 (52.9 mg). (C-9), 105.4 (C-10), 121.3 (C-1′), 113.6 (C-2′), 145.8 (C-3′), 150.0 (C- Centropogin A (1): Yellow amorphous powder, yielded a positive 4′), 116.0 (C-5′), 119.2 (C-6′), 98.5 (Xyl-1), 75.7 (Xyl-2), 76.6 (Xyl-3), response to the Shinoda test; HRESIMS (positive mode) m/z 603.1310 69.4 (Xyl-4), 65.7 (Xyl-5), 108.9 (Api-1), 76.1 (Api-2), 79.3 (Api-3), 74.0 + 1 [M+Na] (calcd.