Indian Journal of Chemistry Vol. 46B, May 2007, pp. 872-874 Note A new flavone glycoside from Zanthoxylum acanthopodium DC B Ravindra Babu, Shilpi Khurana, Rajeev Sakhuja, Amit K Srivastava & Subhash C Jain* Department of Chemistry, University of Delhi, Delhi 110 007, India E-mail: jainsc48@hotmail.com Received 27 December 2005; accepted (revised) 4 January 2007 Examination of the dry fruits of Zanthoxylum acanthopodium has led to the isolation of a new flavone glycoside along with herbacetin-8,4'-dimethyl ether. The new flavone glycoside is characterized as 7-O-α-D-glucosyl-3,8-dihydroxy-2-(3-hydroxy-4- methoxyphenyl)-5-methoxy-4H-1-benzopyran-4-one on the basis of its spectral studies and that of its aglycone. This is the first report of the isolation of a 5-O-substituted flavone from the genus Zanthoxylum. Keywords: Zanthoxylum acanthopodium DC, fruits, rutaceae, flavone glycoside, 7-O-α-D-glucosyl-3,8-dihydroxy-2-(3- hydroxy-4-methoxyphenyl)-5-methoxy-4H-1-benzopyran-4-one, herbacetin-8,4'-dimethyl ether IPC: Int.Cl. 8 C07D The fruits of Z. acanthopodium (Rutaceae) are commonly known in India as Tambul. They possess the peculiar flavour of coriander and have long been used as a spice. The fruits are extensively used in the Ayurvedic and Unani systems of medicine 1 . Previous phytochemical investigations of the fruits and seeds had led to the isolation of herbacetin-7,8,4'-trimethyl ether 2-5 (tambulin, 1) and 8-O-glucosyl-gossypetin- 7,4'-dimethyl ether 6,7 (tambuletin, 2). The fruits have now been re-examined and herein are reported two flavonols 3 and 4. Compound 3 is identified as herbacetin-8,4'-dimethyl ether 8,9 while 4 is a new flavone glycoside. A number of flavone glycosides have also been reported earlier from various natural sources 10 . Compound 4 gave positive Molisch's and Shinoda's tests, indicating it to be a flavone glycoside. Its IR spectrum had strong absorption bands at 3370 and 1658 cm -1 showing the presence of free hydroxyl(s) and a flavonoid carbonyl respectively in the molecule. The presence of the flavonoid skeleton was also supported by its UV-Vis spectrum 11 which exhibited absorption maxima at 258 and 376 nm. Further, a bathochromic shift of 62 nm in band-I observed in the presence of AlCl 3 was typical of a flavonoid containing 3-hydroxyl group 11 . The spectrum remained unaffected in the presence of sodium acetate suggesting thereby that either C-7 is unsubstituted or C-7 hydroxyl is blocked; the former possibility however looked rather remote and unlikely on biogenetic grounds. Careful interpretation of the 1 H NMR spectrum corroborated the previous findings and also revealed the presence of two methoxyls and a sugar unit. The glycoside 4 was hydrolysed and the sugar moiety obtained was identified as D-glucose by its comparison with the authentic sample on paper chromatography in n-BuOH:pyridine:H 2 O (6:4:3). The GLC chromatogram of its TMS derivative was also comparable with that of the standard sample. The aglycone 5 gave a molecular ion peak at m/z 346 corresponding to the molecular formulae C 17 H 14 O 8 . The substitution pattern in ring A and B was deduced by considering its mass fragmentation pattern along with the UV-Vis and 1 H NMR data. A fragment ion at m/z 151 (due to retro Diels-Alder cleavage) indicated ring B to contain a hydroxy and a methoxy group. The presence of a 3′,4′-dioxygenation pattern was indicated by its 1 H NMR spectrum as it showed peaks characteristic of 1,2,4-trisubstituted aromatic moiety at δ 7.10 (d), 7.77 (d) and 7.84 (dd). The hydroxy group was placed at C-3′ and the methoxy at C-4′ on the basis of its UV-Vis data. A bathochromic shift of 39 nm in band-I with a decreased intensity on addition of sodium methoxide (characteristic of a 3-hydroxy flavone lacking 4'-OH) indicated that the C-4′ hydroxyl is substituted and hence the methoxy was placed at C-4′. Further EIMS data showed another important ion at m/z 181 (for A + - H) thus indicating the presence of two hydroxy and a methoxy in ring A. The two hydroxy were present as ortho-dihydroxy and placed at C-7 and C-8 based on its UV-Vis spectrum. The presence of C-7 hydroxyl was indicated by a bathochromic shift of 9 nm in band-II on addition of fused NaOAc. This maxima further shifted by 11 nm on addition of H 3 BO 3 (typical for o-dihydroxy groups) which supported the presence of C-8 hydroxy. The absence of any peak in the region δ 94.0-100.0 in its 13 C NMR spectrum