Pergamon Phytochemistry, Vol. 44, No. 1, pp. 187-190, 1997 Copyright ~ 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved PH: S0031-9422(96)00465-7 0031-9422/97 S17.00 + 0.00 C-p-HYDROXYBENZOYLGLYCOFLAVONES FROM CITRULLUS COLOCYNTHIS GALALT. MAATOOQ, SALEH H. EL-SnARKAWY*, M. S. AF~ and JACKP. N. ROSAZZA~" Dept. of Pharmacognosy, Faculty of Pharmacy, Universityof Mansoura, Mansoura 35516, Egypt; tCenter for Biocatalysis and Bioprocessing,College of Pharmacy, University of Iowa, Iowa City, IA 52242, U.S.A. (Received in revisedform 30 April 1996) Key Word Inflex--Citrullus colocynthis; Cucurbitaceae; C-linked flavone C-glucoside; C-p- hydroxybenzoylisoorientin; vitexin; isovitexin 4'-O-glucoside. Abstract--In a flavonoid investigation of the fruits and aerial parts of Citrullus colocynthis six flavone C-glycosides were identified. The fruits contained isovitexin, iso-orientin and iso-orientin 3'-methyl ether, while the aerial parts contained three new C-p-hydroxybenzyl derivatives, viz. 8-C-p-hydroxybenzoylisovitexin, 6-C-p- hydroxybenzoylvitexin, and 8-C-p-hydroxybenzoylisovitexin4'-O-glucoside. Their chemical identity was estab- fished by NMR spectroscopic methods including 2D-NMR, as well as UV and MS analyses. Copyright © 1996 Elsevier Science Ltd INTRODUCTION showed similar spectral data to isoorientin (2), [8] and its [M] ÷ showed m/z 462 indicating the addition of a The fruits of Citrullus colocynthis Schrad (Cucur- bitaceae) are well known for their medicinal properties methyl group to 2. Addition of AIC13 and A1CI3/HCI [1]. Several cucurbitacins have been reported [2, 3] but reagents to 1 gave bathochromic shifts of 53 nm (from 337 to 390 nm) [9]. The absence of the catechol at ring there are no records of the flavonoid constituents of C. B was confirmed by the NaOAc/H3BO 3 spectrum colocynthis. However, flavone C-glycosides have been which gave no bathochromic shift at 337 nm band isolated from other members of the Cucurbitaceae [4- while a 55 nm bathochromic shift in band-I of NaOAc 6]. The present paper describes the isolation, purification spectrum showed the absence of a free 4'-hydroxyl and the 5.5 nm bathochromic shift of band-II indicated the and structure eludication of the glycoflavones of the fruits and aerial parts of C. colocynthis, presence of a free 7-hydroxyl. This was supported by the presence of 336 nm shoulder in the NaOAc spectrum [10, 11]. The 1H NMR of 1 showed a doublet RESULTSANDDISCUSSION at 6H4.62 (1H, J=9.8 Hz, Hi. ) suggesting an anomeric proton of a t-linked sugar [4] and the The methanolic extract of powdered C. colocynthis presence of the methyl group was supported by t~ n 3.9 fruits was purified by column chromatography (CC) on singlet and 6 c 55.84 signals. The signal at 6 c 108.72 a Sephadex LH20 to give two fractions rich in flavo- noids. Further purification afforded isoorientin 3'- ppm was assigned to a C6-1inked to the sugar (normally between 96-98 ppm) and its connectivity was con- methyl ether (1), isoorientin (2), and isovitexin (3) [7]. firmed by a selective INEPT experiment where irradia- The aerial parts were treated similarly on silica gel CC tion of the anomeric proton at t~ 4.62 enhanced the and further purification on preparative TLC resulted in carbon signals at 6c 108.72 (C6) and 6 c (163.24 (C7). three new flavone C-glycosides, viz. 8-C-p-hydroxy- Compounds 2 and 3 were identified by comparison benzoylisovitexin (4), 6-C-p-hydroxybenzoylvitexin of their physical properties and spectral analyses with (5), and 8-C-p-hydroxybenzoylisovitexin 4'O-t-D- reported data [7, 8]. glucoside (6). The identity of the isolated flavonoids The ELMS of 4, from the aerial parts, gave a was achieved using extensive UV, MS and NMR molecular ion at m/z 538 for CEsH26OH. The IH NMR spectroscopic analyses. The complete 13C NMR data spectral data (Table 1) showed four doublets (each of 2 are given in Table 1, and additionally confirmed by protons) in two aromatic AB systems, viz. 6 n 7.8 and 2D-COSY, HETCOR, Selective INEPT experiments for 6.92 (J = 7.5 Hz) corresponding to H2,6, and Ha. , 5' of the first time. Isoorientin 3'-methyl ether (1) from the fruits ring B, and ~7.07 and 6.63 (J=7.8 Hz) corre- sponding to H2..6,. and H3.,5,, of ring D. The 13C NMR data (Table 1) showed 6 c 127.99, 128.70, 115.81, and *Author to whom correspondence should be addressed. 114.77 shifts assigned to C2,.6, and C2°6, and C3,.5,, 187