Phytochemistry, Vol. 20, No. 8, pp. 1947-1950, Printed in Great Britain. VISMIAQUINONE, 0031-9422/81/081947+4 $02.00/O #T 1981 PergamonPressLtd. 1981. zyxwvutsrqponmlkjih zyxwv A A’-ISOPENTENYL SUBSTITUTED ANTHRAQUINONE FROM zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCB VISMIA REICHARDTIANA MARIA DE LOURDES S. GONCALVES and WALTER B. MORS Nticlec de Pesquisas de Produtos Naturais, Centro de C&I&S da Satide, Bloco H, Universidade Federal do Rio de Janeiro, 21941 Rio de Janeiro, Brazil (Revised received 14 JzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPON anuary 1981) Key Word Index-Vismiareichardtiuna; Guttiferae; anthraquinone; A’-isopentenyl side chain; biogenesis. Abstraet-l,I-Dihydroxy-7-(A’-isopentenyl)-6-methoxy-3-methylanthraq~none (vismiaquinone) was isolated from the leaves of vismia reichurdfianu. Its structure was established through chemical and spectral means. A hypothesis for the biogenesis of the uncommon A’-isopentenyl side chain is presented. INTRODUCTION In a recent paper [l 1,Delle Monache et al. described the anthraquinone 1 as a transformation product of vismione A, a tetrahydroanthracene derivative from the fruits of Vismiu bacciferu (L.) Tr. et Pl. subsp. deulbuta (H.B.K.) Ewan (Guttiferae). We report our findings on compound 1, for which the name vismiaquinone is proposed, as a genuine constituent of the leaves of Vismiu reichurdtiuna (0. Ktze.) Ewan from the north-northeastern part of Brazil. Our material .was collected in the vicinity of SBo Luis, the capital city of the state of Maranhb. The plant, a large shrub, is known under the popular name of ‘lacre’. This, as well as several other Vimia species, yields a redorange coloured gum-resin as a stem exudate, which during the 19th century was an article of commerce known as ‘American gwnmi guttae’ . Used as a substitute for the genuine gummi guttue obtained from Asian Garcinia species, the product had applic&ns as a constituent of water-colours, a drastic purgative and a topical remedy for skin diseases. The latter use persists in Brazilian folk medicine to this day. RESULTS AND DISCUSSION Vismiaquinone (1) was isolated from the petrol extract of the dried leaves of K reichardtiuna by chromatography (see Experimental, procedure A). That the substance is not an artefact produced during isolation and purification was ascertained by a second extraction with petrol and its separation through direct crystallization under careful manipulation, avoiding all contact with reagents and adsorbents (procedure B). OH 0 ij 1 Vismiaquinone OH The pure, red crystals melt at 202-204”. Elemental analysis furnishes the molecular formula C,,H,,O,. IR absorptions suggest the presence of either highly conjugated carbonyl groups or double bonds, as well as an aromatic character. The same is evident from the ‘H NMR spectrum, with broad signals for two aromatic protons suggesting mfrtu-coupling. The presence of phenolic groups is indicated by two signals downfield integrating for one proton each, exchangeable with D,O. Two phenolic hydroxyl groups were further confirmed by preparation of a diacetate. A singlet corresponding to three protons, at 6 4.02, indicates the presence of one methoxyl group. A doublet integrating for one proton (J = 16Hz) appears at 6 6.6 and is attributed to a trans-double bond, corroborated also in the IR by an absorption at 971 cm:‘. The position in the ‘H NMR spectrum indicates conjugation with an aromatic ring Upfield appears a doublet centred at 6 1.14, corresponding to six protons (J = 6.5 I-Ix), possibly belonging to two geminal methyl groups, coupled with one proton appearing as a multiplet centred at 6 2.48. This suggests the presence of an isopropyl group in the structure. Selective decoupling of the last-mentioned proton caused simplification of the doublet, thus conRrming this assumption. Also observed was an alteration in a multiplet located in the region between 6 6.8 and 7.0 and corresponding to one olefinic proton. This indicates that the isopropyl group is a to the double bond in conjugation with an aromatic ring. The spectrum in the W/visible region, besides con6rming the phenolic nature through a bathochromic shift in alkali also strongly suggested a quinone structure, possibly a hydroxyanthraquinone. A chrysazine system is suggested by the presence of a strong absorption at 445 nm (log E 4.2). The quinone nature was confirmed by reduction with sodium borohydride, which caused decolouration, the colour being restored by oxygen. Extraction of 1 from a benzene solution with aqueous alkali produced a colour change to violet, reproducing the classical Bomtrager reaction for hydroxyanthraquinones. Also on paper and thin layer chromatograms, the orange colour changed to red when exposed to ammonia vapour. 1947 M. 1950 DE L. S. GONCALVES Toledo Rizzini of the Rio de Janeiro Botanic Garden for identification of the plant material. Thanks are also due to Prof. Antonio Jorge Ribeiro da Silva for his assistance in obtaining the ‘“C NMR spectra and Prof. Roderick A. Barnes for discussions. RFXFXENCES and W. B. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR MORS 6. Dave, K. G., Mani, R. and Venkataraman, K. (1961) J. Sci. Ind. Res. (India) 2lJ& 112. 7. Rao, A. V. R., Rathi, S. S. and Venkataraman, K. (1972) Indian .I. Chem. 10,989. 8. Venkataraman, K. (1975) in The Flauonoids (Harborne, J. B., Mabry, T. J. and Mabry, H., eds.) p. 267. Chapman St Hall, London. 9. Birch, A. J. (1957) in Progress in the Chemistry of Organic Natural Products (Zechmeister, L., ed.) Vol. 14, p. 186. Springer, Vienna. 10. Yamazaki, M. and Shibata, S. (1966) Chem Pharm. Bull. 1. Delle Monache, F., Ferrari, F., Marini-Bettblo, G.-B., Maxfield, P., Cenini, S., Fedeli, W., Gavuzzo, E. and Vaciago, A. (1979) Gazz. Chim. Ital. 109, 301. 2. Hafle, G. (1977) Tetrahedron 33,1963. (Jpn) 14,96. 3. Thomson, R. H. (1971) Naturally Occurring Quinones, 2nd edn. Academic Press, London. 11. Birch, A. J. (1965)in Proc. Fed. Eur. Biochem Sot. (Billek, G., ed.) 2nd edn, p. 3. Pergamon Press, Oxford 4. Ballantine, J. A. and Pillinger, C. T. (1967) Tetrahedron 23, 12. Ritchie, E. and Taylor, W. C. (1964) Tetrahedron Letters 1691. 1431. Chem. Sot. 1355. 5. Hooker, S. C. (1896) J. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA