Chemical investigation of Polylepis incana (Rosaceae)

~ Pergamon 0305-1978(95)E00075-1 Biochemical SystemaO'cs and Ecology, Vol. 23, No, 1, pp. 105--107, 1995 Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0305-1978/95 $9.50 + 0.00 Chemical Investigation of Polylepis incana (Rosaceae) S. CATALANO,*$ P. L. CIONI,* M. MARTINOZZI,* V. DE FEOt and I. MORELLI* *Dipartimento di Chimica Bioorganica della Facolt~ di Farmacia, Universit~ degli Studi di Piss, Via Bonanno 33, 56126 Piss, Italy; tDipartimento di Chimica delle Sostanze naturali, Univerait~ degli Studi di Napoli "Federico I1", Via D. Montesano 49, 80131 Napoli, Italy Key Word Index--Polylepis incana; Rosaceae; Rosoideae; Sanguisorbeae; triterpenes; flavonoids; chemotaxonomy. Abstract--Triterpenes and flavonoids isolated from Polylepis incana confirm the correct systematic position of the species in the tribe Sanguisorbeae (Rosoideae). Introduction Polylepis incana H.B.K. (Rosaceae), a tree about 5-8 m high, grows on plateaux of the Andean Cordillera at 2400-5200 m in Ecuador (Pichinca, Cotopaxi, Tungurahua), and Peru (Ancash, Pasco, Cuzco). In our previous work the plant had been subjected to a chemical study that lead to the isolation and characterization of a new flavonoid compound, kaempferol 3-O-I]-D-(6"-feruloylglucoside), named incanoside (Catalano et al,, in press). This paper deals with the isolation of the triterpenoidic and flavonoidic compounds which have a chemotaxonomic value in the Rosaceae family (Hegnauer, 1990). Materials and Methods Column chromatography. Sephadex LH20 (Pharmacia Fine Chemicals), Silica gel (Meck 70-230 and 230-410 mesh), Lobar RP8 (Merck) were employed for column chromatography. HPLC. Apparatus Waters 600 E (Millipore), Photodiode Array Detector Waters. Column Lichrospher 100 DIOL (5 tl) (LichroCart 250-4) isocratic, eluent chloroform-methanol-acetonitril (87:9:4), flow 1.1 ml min =1, ;~ax=270 nm. IH and13C NMR. Spectra were recorded with a Bruker AC 200; the solvent used was CD3OD and internal reference was TMS. Plant material Polylepis incana was collected during September 1992 in Paruso region (Cuzco in Peru. Voucher specimen is deposited in the herbarium of the Museo de Historia Natural "Javier Prado" de la Universidad Nacional de San Marcos-Lima. Extraction and isola~'on. The dried aerial parts (450 g), extracted in the following order with hexane (22 h), chloroform (20 h), chloroform-methanol 9:1 (44 h) in a Soxhlet apparatus and with methanol at room temp. (6 weeks), gave 17.44, 10.83, 22.0 and 45.23 g of residues respectively. A portion (10.0g) of the chloroform extract was fractionated by gel filtration on a Sephadex LH20 column chromatography using chloroform-methanol (1:1) as eluent, to give 11 fractions (I-Xl). 2(x,31}-Dihydroxyursolic acid (corosolic acid) 1 and 2c(,3~,19(z- trihydroxyuraolic acid (tormentic acid) 2 were obtained from fraction VI after flash and gravity chromatography on silica gel; 2¢,31],19(x,23-tetrahydroxyursolic acid (23-hydroxytormentic acid) 3 was isolated from fraction VII by preparative TLC on silica gel. A portion (10.0 g) of the chloroform-methanol extract was fractionated, as described previously, using methanol as eluent to give 25 fractions (I--XXV). 20~,31[},190{-23-Tetrahydroxyursolic acid 28-O-I]-e-glucopyranosylester (nigaichigoside) 4 and catechin 5 were obtained from fractions Vl and XVI, respectively using RP 18 column chromatography, while quercetin-3- galactoside 6, quercetin-3-glucoside 7, quercetin-3-arabinoside 8, and kaempferol-3-O-I]-o-(6"-feruloyl) gluco- pyranoside (incanoside) 9 were isolated from fraction XVll using Sephadex LH 20 and preparative TLC on silica gel for compound 6 and preparative HPLC for compounds 7, 8 and 9. Kaempferol-3-O-l[}-o-(6"p- coumaroyl) glucopyranoside (tiliroside) 10 and apigenin 11 were obtained from fraction XlX by preparative TLC on silica gel, while fractions XXlI, XXlV and XXV, by crystallization with methanol, gave luteolin 12, kaempferol 13, and quercetin 14, respectively. Chemical structures of compounds 1-10 are shown in Fig. 1. tAuthor to whom correspondence should be addressed. (Received 17 June 1994) 105 106 S. CATALANO ETAL. _= R ":- • ~COOl~ 1 R = RI = R2 = H corosolic acid 2 R= OH; Rl= 1~= H tormentic acid 3 R=Rx = OH;I~=H 23-hydroxytormentic acid 4 R = R1 = OH; R2 = O-I~-D-glucopiranosyl nigaichigoside R H O ~ 0 ~ ~/OH ~ O H H I II II o "c - -c j ~ '~ - , . o' . 'o' o 9 R = -OMe incanoside 10 R = H tiliroside FIG. 1. STRUCTURES OF TRITERPENOIDIC AND FLAVONOIDIC COMPOUNDS ISOLATED FROM R iNCANA. The compounds were characterized by direct comparison (UV, IR, ~H and 13C NMR) with authentic samples and with published data (Agrawal, 1989; Connolly and Hill, 1991). Results and Discussion The 190~-hydroxyursolic acid derivatives are known to be characteristic of Rosoideae subfamily (Kuang et al., 1989) and the highest hydroxylated compounds like nigaichi- goside 4 and 23-hydroxytormentic acid 3 for the tribe Sanguisorbeae (Reher and Budesinsky, 1992) and Rubeae (Ohtani et ai., 1990, 1992; Zhou et al., 1992). All these compounds seem to show a correct systematic position of Polylepis incana as regards the chemistry of triterpenoids. It must be pointed out the existence of a chemical relationship between R incana (tribe Sanguisorbeae) and Geum japonicum Thunberg (tribe Dryadeae-Geinae)(Shigenaga et aL, 1985) due to ursane derivatives 1, 2, 3 and 4 simultaneously present only in these two Rosoideae species. The occurrence of the flavonoids apigenin 11, luteolin 12, kaempferol 13, quercetin- 3-O-galactoside 6, quercetin-3-O-glucoside 7, and quercetin-3-O-arabinoside 8 which are common components in Rosaceae (Hegnauer, 1990) seems to agree, from a chemical point of view, with the belonging of Polylepis incana to this family. Tiliroside 10, previously identified in Tilia argentea Desf. (Tiliaceae) (HSrhammer et al., 1961), Phlomis spectabilis Falc. ex Benth. (Labiatae) (Kumar et al., 1985), Eremocarpus setigerus (Hook) Benth.(Euphorbiaceae) (Bajaj et al., 1986), Daphne genkwa Sieb et Zucc. (Thymelaeaceae) (Nikaido et al., 1987), Althaea spp. (Malvaceae) (Gudej and Bieganowska, 1990), Helichrysum pamphilicum (Compositae) (Sezik and Akdemir, 1986) and Quercus spp. (Fagaceae) (Romussi et al., 1988, 1991a,b), was previously CHEMICAL INVESTIGATION OF R INCANA 107 isolated in Rosaceae only from Rosa canina L. (H6rhammer eta/., 1961), Rosa davurica Pall. (Roseae) (Kuang, 1989) Rubus plicatus (Rubeae) (Wojcik, 1989), and now in Polylepis incana. This compound found until now in Roseae, Rubeae and Sanguisorbeae might be introduced as chemotaxonomic marker of subfamily Rosoideaeo Incanoside 9, identified only in Polylepis incana (Catalano et al., in press), has a structure very close to that of tiliroside and joined with the latter could be used as a more specific chemotaxonomic marker. References Agrawal, P. K. (1989) Carbon-13-NMR of Flavonoids. Elsevier, Amsterdam. Bajaj, R., Chang, C. J. and McLaughlin, J. L. (1986) Tiliroside from the seeds of Eremocarpus sedgerus Hook. J. Nat. Prod. 49, 1174-1175. Catalano, S., Bilia, A. R., Martinozzi, M. and Morelli, I. (in press) A new acyl glucoside from Polylepis incana. Phytochemistry. Connolly, J. D. and Hilll R. A. (1991) Dic~'onary of Terpenoids. Chapman & Hall, Cambridge (and references cited therein). Gudej, J. and Bieganowska, M. L. 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