003 I -9422/86 53.00 + 0.00 Phymchmirrry, Vol. 25. No. 10, pp. 2351-2355, 1986. Printed in Great Britain. PcrgamonJournalsLtd. XANTHONES FROM THREE GARCINIA SPECIES zyxwvutsrqponmlkjihgfedcba STEPHEN A. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA AM POFO* and PJZTER G. WATERMAN? Phytochcmistry Research Laboratories, went of Pharmacy (Warm. Chem.), University of Strathclydc. Glasgow GI I=, Scotland, U.K. (Received Key Word Index-Garcinia nerwq 2 January 1986) G. polyanthn; G. pyrifero; Guttiferae; 1,3,6,7_oxygenatedxanthones; 1,3,5,6- oxygeoatcd xanthoncs; chemotaxonomy. AhatraceFrom the stem bark of three previously uninvestigated Garcinia species a number of xanthones have been isolated including three that appear to be novel. The novel compounds are characterized as isocowanin (8-gemnyl-4 (3,3-dimethylaUyl)-7-methoxy-1,3,6-trihydroxyxanthone), isocowanol (8-geranyl4(3-hydroxymethyl-3-methylal 7-methoxy-1,3,6_trihydroxyxanthone) and nervosaxanthone (4,8-di(3,3dimethylallyl)-2-(l,ldimethylallyl)-l,3,5,6tetrahydroxyxanthone). The chemotaxonomic significance of oxygenation patterns in these xanthones is briefly discussed. INTRODUCIION genus Garcinia is widespread in the old World, most notably in the lowland tropical rain forests of south-east Asia and west Africa [ 11.The genus has been the subject of a considerable amount of phytochemical investigation which has revealed it to be a major source of prenylated xanthones and benzophenones and of billavonoids linked between C-3 and C-8 [2]. In this paper we report the results of a study of the stem barks of three previously uninvestigated spies, G. nervosu Miq., G. pyrifera Ridl., both collected in west Malaysia, and G. polyanth Oh., collected in Cameroon. From each of the above xanthones were obtained, three of the isolated compounds appearing to be novel. The findings are also discussed in the light of a recent paper [2] on the chemotaxonomy of Gmciniu and allied genera of the Guttiferae, tribe Garcinieae. The (613.38) at C-l and three aromatic protons as a metacoupled AB quartet (66.19 and 6.29) for H-2and H-4 and a singlet at 66.81 (H-S). A single methoxy resonance occur- ‘:: 7’I 6 5’ 4 2’ 3” Me0 m 0 OH ” 8 7’1 ‘5 R2 q 1’2 IO g 0 3m I? RESULTS AND DISCUSSION Garcinia pyriferu is a small tree of lowland forest distributed throughout the Malayan peninsula, Sumatra and Borneo [3]. Extraction of the stem bark with petrol and then ethyl acetate revealed identical mixtures which were bulked and subjected to column chromatography from which two triterpenes and three xanthones were obtained. The former were identified as /3-amyrin and oleanolic aldehyde. The three xanthones analysed for C,,H,,O,, C,,H,,O, and Cz9H3*07 and were identified as rubraxanthone (1). isocowanin (2) and isocowanol (3), respectively. The UV spectrum of 1 was typical of a 1,3,6,7oxygenated xanthone and showed bathochromic shifts with AICIJ and NaOAc indicative of free hydroxy groups at C-l and at C-3 or C-6 [4,5]. The ‘H NMR spectrum revealed signals for an H-bonded hydroxy function I R-R’ -I?‘-H 2 R - @ = H, R’ - C+CH=CNk~ 3 R - R2 - Ii, R’ - CH,CH=CM&H@H 5 R - Me, R’ - CH&P=CMe)2, 6 R = R’ = H, R2 = CH,CH=Cblc), 7 R - R’ - H, ti - CJ4,CJi=C(tvleKl+OH *Present address: Department of Chemistry, University of Iowa, Iowa City, U.S.A. tAuthor to whom correspondence R’ 4 should be addressed. 2351 R2- H [I - Ill]’ S. A. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA AM P~FOand P. G. WATERMAN 2352 red at 63.80. The remaining non-replaceable protons unit at C-4 was indicated by the ’ % JNM R spectrum of the appeared as a series of signals typical of a geranyl moiety. fully methylated derivative 5 (Table 1) in which three of the most important feature being the deshielded position the methyl resonances were shielded and one deshielded. of the methylene group adjacent to the aromatic nucleus By contrast placement of the prenyl unit at C-2 would (64.12) indicating its location at C-8, peri to the carbonyl. have led to deshielding of two of the methyl resonances, The presence of a geranyl unit was confirmed by major those for C-l and C-7. On this basis the xanthone must be ions at [M -69]+ and [M - 1231’ in the mass spectrum assigned structure 2. It has been given the trivial name of while its placement at C-8 was indicated by [M - 1111’ isocowanin since it is isomeric with the known xanthone (4) a fragment typical of 8-geranyl-7-methoxy xanthones cowanin (6) reported from G. cowu 193. [6]. The ‘%NMR spectrum (Table 1) was recorded for Isocowanol(3) gave ‘H NMR data identical to 2 except the first time and resonance positions assigned by comfor the loss of one methyl resonance and its replacement parison with data for other xanthones [7]. It was particuby a broad singlet (2H) at 64.40. indicative of a hylarly valuable in placing the methoxy group at C-7 due to droxymethyl group and therefore accounting for the its relatively deshielded resonance position (61.4 ppm) additional oxygen in the empirical formula. The which required that both ortho positions be substituted. hydroxymethyl group was located in the A-ring prenyl Rubraxanthone has previously been isolated from two substituent by the continued occurrence of the ion 4 as a other Asian species, G. cowu Roxb. [6] and G. rubra Merr. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJI feature of the mass spectrum. Once again the 13C NMR spectrum of the fully methylated derivative (Tabk 1) PI. The ‘HNMR spectrum of 2 agreed with that for 1 established that the pretty1 unit was at C-4, not C-2. except for the loss of one of the A-ring protons, leaving a Accordingly 3 has been assigned the trivial name isosinglet at 66.26, and by additional signals for a 3,3- cowanol and is also isomeric with a xanthone from dimethylallyl unit. The continuing presence of the geranyl G. cowu, in this case cowanol (7) [9]. moiety at C-8 was confirmed from the mass spectrum (ion Garcinia wvosa Miq. (syn. G. andersonii Hook.) is 4) and the methoxy group at C-7 by the ‘%NMR found particularly near water, its range being similar to spectrum (Table 1). Placement of the additional prenyl that of G. pyrijera but extending to the Phillipines [3]. Table Carbon 1. ‘sC NMR chemical shifts for xanthones 1 and 2 and the methykted of 2 and 3t number 1 2 3 4 4a 5 6 7 8 8a 9 9a 1Qa I’ 2’ 3 3’-Me 4 5’ 6 7’ 7tMe)s 1” 2” 3” 3”-Me 3”-Me or CH,OH OMe 1 165.4. 98.8 164.9. 93.8 156.3.. 102.8 157.5.. 144.7 138.3 112.0 182.7 103.0 156.6.. 27.3 124.8*** 135.1 16.6 40.2 26.8 125.2+** 131.5 17.7125.8 - - 61.4 2 162.7. 98.3 162.5. 106.4 159.5 102.9 155.1.. 144.6 138.2 111.8 183.1 104.0 156.4.. 27.3 124.1’** 135.1 16.6 40.4 26.8 125.2*** 131.4**** 17.7125.8 22.1 123.5 131.5**** 25.7 18.1 61.5 tOMe, 90.5 97.7 - - derivatives 3-OMe. 90.7 97.7 - 26. I 124.1. 26.0 125.8, - 16.1 39.6 26.6 123.9. 16.2 39.8 26.8 124.6. 17.6n5.7 21.6 122.2. 17.5125.5 21.3.. 124.0’ 25.5 21.4.. 18.1 6&l/56.2/ 55.8155.7 61.7 60.7156.31 55.9155.8 t Resonanas in the same column with the same number ofasterisks are interchangeabk. Spectra of 1 and 2 were obtained at 62.5 MHz in Me&O-d, and those for the methylated xanthones at 90.56 MHz in CDCI, Xanthoncs from Garcinia Identical treatment of the stem hark gave a mixture of sitosterol and stigmasterol, 1 and a second xanthone which analysed for C,sH,,O,. This last compound, which has been given the trivial name of nervosaxanthone, was assigned structure 8 on the basis of the following evidence. Nervosaxanthone gave a UV spectrum for a 1,356 tetraoxygenated xanthone [S] and on acetylation gave a tetra-acetate indicating that all four were free hydroxy substituents. The ‘H NMR spectrum revealed signals for two 3,3-dimethylallyl and one 1,ldimethylallyl substituents, one of the former being pktced at C-8 due to the deshielding of the Ar-CH, resonance to 64.09 because of its position peri to the carbonyl. A single aromatic proton occured at 67.22, typical of H-7, leaving the other two prenyl units to occupy C-2 and C-4. The remaining problem, the relative placement of the other 3,3-dimethylally1 and the 1,ldimethylallyl unit at C-2 and C-4, was resolved by preparation of the tri- and tetraacetates. A comparison of their ‘HNMR spectra revealed that additional acetylation of C- 1 caused appreciable shifts in one of the methyl groups and the vinylic methine proton of the 1,ldimethylallyl group which must therefore be placed at C-2. On this basis nervosaxanthone must be 8. The final species to be examined, Garciniu polyantha Oliv. (syn. G. bmteri Oliv., G. cheuolieri Engl.), is a tree of the rain forest canopy found throughout west Africa [lo]. From the stem bark extracts three compounds were obtained, a xanthone (C,,H,,O,), and the benzophenones xanthochymol and isoxanthochymol which were identified by direct comparison to authentic material [ll]. Analysis of the UV and ‘H NMR spectra of the xanthone revealed a 1,3,5$-oxygenated compound substituted at C-2 and C-4 with 1,ldimethylallyl units, with one of those units cyclized onto the C-3 hydroxyl function. These data comply with the two known compounds rheediaxanthone-B (9) and isorheediaxanthoneg (10). The identity of the compound as 10 was conlirmed by a comparison of ‘H spectra (2SOMHz) of the isolated compound and its diacetate with authentic material of 10 and the diacetate 11. Comprehensive ‘HNMR data on 10 and 11 have not been previously published and it is considered worthwhile to do so here (Table 2) as these 2353 data readily allow differentiation between the two isomers. These tindings make a useful additional contribution to the development of a chemotaxonomic profile for Gurcinia [2]. According to Engler [ 121 G. polyantha is placed in Gurcinia section Rheediopsis together with G. ovali$olia and G. staudtii. This group of taxa is characterized by (a) the production of 1,3,5$-oxygenated xanthones carrying prenyl substituents at C-2 and C-4 and (b) by the presence of xanthochymol. This section also shows close biochemical ties to the genus Rheediopsis which has been the source of some of the same and other similar xanthones [13-151. Garcinia pyrijma was unassigned by Engler [123 but clearly shows a close biochemical similarity to investigated species of the section zyxwvutsrqponmlkjih Oxycarpus, G. cowa and G. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJ rubra, all three producing 7-methoxy1,3,6_trihydroxyxanthones with a geranyl substituent at C-8. Garcinia nervosa, under the name G. andersonii, was assigned by Engler [12] to the section Xanthochymus which includes species from south east Asia, India and west Africa. Previous work on five other species has not shown a cohesive biochemical profile in either xanthone or benzophenone production but all five do produce tlavanone/flavone dimers. The addition of data for G. newosa does nothing to resolve the complex picture in this section; the presence of 1,3,5,6-substituted xanthones (cf. nervosaxanthone) had been reported from one other species, G. densivenia [2,14], but this is the first record of 1,3,5,6_substitution in Asian taxa of this section. Furthermore no biflavonoids were detected in this present investigation. In the light of the chemical homogeneity shown by the taxa in some of Engler’s sections of Gurciniu, notably Rheediopsis and Oxycarpus, the application of xanthone markers in the genus seems to hold some taxonomic promise. However, if this is the case then the chemical data points out the need to look critically at section Xanthochymus. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO EXPERIMENTAL Plant material. Stem barks of G. pyrifero and G. ner~sa were collected in the Ku& Lompat study area of the Krau Game OH / :I * 1; OH HO A 8 9 0 :I Ro 0 OH ‘Co Ro * IO R-H zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA II R-AC 2354 S. A. AMPOFOand P. G. WATERMAN Table 2. ‘HNMR chemical shifts for rheedkuanthone B (9). isorhcediaxanthonc B (10) and isorheediaxanthone B diacetate (11) Signal 9 10 11 OH-l s 14.08 13.24 13.10 H-7 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA d 6.93 (8.8) 6.94 (8.7) 7.21 (8.7) H-8 d 7.77 (8.8) 7.68 (8.7) 8.13 (8.7) Furan ring H-2’ g 2’-Me d 3’-(Me), s s 4.45 (6.6) 1.39 (6.6) 1.57 1.59 4.45 (6.3) 1.39 (6.3) 1.60 1.60 4.43 (6.2) 1.36 (6.2) 1.63 1.63 1.31 1.56 6.35 (17.4, 10.7) 4.95 (17.4, 1.4) 1.26 1.50 6.66 (17.8. 10.5) 5.24(17.8, 1.4) 1.26 1.48 6.18-6.29. 4.904 4.89(10.7. 5.08 (10.5. 1.4) 4.82-4.86’ Open sidechain 1”-Me s I.-Me s 2--H dd 3”-H 3”-H dd 1.4) Spaztra run at 250 MHz in CLXI,. J values in parentheses. *Coupling not first order. Reserve, west Malaysia and vouchers are deposited at the herbarium of the Universiti Kebmgsaan Malaysia. Gmcinia Me,CO-d,:d1.53,1.57,1.83 (3 x 3H,3x s.3 x Me).3.80(3H,s.7OMe), 4.12 (2H, d, J = 7 HZ CH,-Ar), 5.05 (1H. m, H-6’), 5.29 polyanrha was collected in the Korup National Park in Cameroon (lH,r,J = 7 H&H-2’),6.19,6.29(2H,ABq,J = 2 Hx,H-2andHand a voucher sample has been deposited at the Herbarium of the 4), 6.81 (lH, s, H-S), 13.38 (lH, s, l-OH). 13CNMR: see Table 1. Missouri Botanic Garden. MS m/z (rel. int.): 410 [Ml’ (47). 341 [M-C,H,]+ (100). 299 Extraction oj stem zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA barks. Ground stem barks were extracted (32)-ion 4, 285 (14). with petrol (bp 40-W) and then EtOAc (G.pyrij-era 5C0g; Isocowanin (2). Yellow clusters from petrol-EtOAc, mp 160”. G. neruosa 600 B; G. polyantha 250 g). In each a~ TLC examinFound: [M] + 478.2339; C,,H,,O, requires 478.2355. ation of concn petrol and EtOAC extracts showed identical UV& nm: 239,256,313,352. IRv_ an-‘: 34C0,1650,1602, profiles of compounds and these were bulked for subsequent 1510. ‘HNMR (90 MH% Me&O-d& 61.64,1.82,1.87 (5 x Me), analysis. 3.45(2H.d.J = 7 Hz,CH,-l”),3.80(3H,s,7-OMe),4.12(2H,d, J Isolation ojcompoundsfiom G. pyrifera. Theconcd extract was = 8 HzCH,-1’), 5.02 (lH, m, CH-6’). 5.29 (2 x lH, 2 x t, CH-2 subjected to CC over silica gel eluting with petrol (bp W) and and CH-2”), 6.26 (lH, s, H-2). 6.87 (lH, s, H-5), 13.40 (lH, s, lthen petrol containing increasing amounts of EtOAc. Elution OH). ‘“CNMR: seeTable 1. Msm/z (rel.int.k478 [Ml’ (62x409 with 3% EtOAc gave crude &amyrin which was purified by (loo),367 (13),355 (16).Compound2(60 mg)wasdissolvedindry circular prep. TLC using the same solvent to give 250 mg pure Me&O (60 ml) and Mel (3 ml) and anhydrous K&O, (2 g) added. The mixture was refluxed for 24 hr with addition of compound (identical in all respects, IR. ‘H NMR, MS, OR, mmp) with an authentic sample. Elution with 4% EtOAcgavea mixture further Me1 and K&O, and then cooled and filtered. Normal from which 2 (400 mg) ppt on standing. The supematant was work-up gave the 1,3,btrimethyl ether of 2 as a white amorphous subjected to circular prep. TLC using silica gel (solvent, solid. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJ UV j,, nm: 250, 300, 340 (no change with NaOH). toluene-EtOAc-AcOH, 95:5:0.5) and gave oleanolic aldehyde ‘HNMR (9OMHz CDCI,): 61.54, 1.60, 1.68, 1.82, 1.89 (5 x C(80 mg). Further elution with 5 % EtOAcpve a sitosterol/stigmaMe), 1.90-2.15 (4H, m, CH,-4’, CH,-5’). 3.50 (2H, CH,-I”), 3.78, 3.95, 3.95, 3.99 (4 x OMe), 4.13 (2H. CH,-I’), 5.02 (lH, CH-6’). sterol mixture and with 10 % EtOAc yielded 1 (350 mg). Finally 5.28 (2H, CH-2’ and CHZ’), 6.37 (1H. H-Z), 6.73 (IH, H-5). elution with 20% EtOAc gave a yellow amorphous solid from “C NMR: see Table 1. which 3 (48 mg) was obtained after circular prep. TLC (solvent, Isocowanol (3). Amorphous solid. Found: [M]’ 494.2308; tolucncEtOAc-AcOH, 5:4: 1). Oleanolic aldehy de. Amorphous solid, [ab +56” (c 0.1; C,,H,,O, rquires 494.2304. W.& nm: 240, 254, 312, 350. CHCI,) (lit. [16] +71”). Found: [M]’ 440.3637; C,,H,sOI IRv_ cm-‘: 3300, 1650, 1605, 1580. ‘HNMR (9OMHz Me&O-d,): 61.57, 1.76, 1.83 (12H, 4 x Me). 1.90-2.20 (4H. m. rquires 440.3654. IR v_ cm-‘: 3400, 1725, 1460, ‘HNMR (90 MHz, CDCI,): 60.78-1.09 (7 xs, 7 x Me), 3.20 (lH, zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA dd, CH,-4’, CH,-S’), 3.55 (2H, d, J = 8 HS CH,-I”), 3.80 (3H, s, 7OMe),4.12 (2H,d, J = 8 Hz, CH,-I’),440 (2H, & s, 3”-CH,OH), J=lO,6Hz.H-3),5.3l(lH,br~,J=4Hz,H-l2),9.32(1H,s,l7CHO). MS m/z rel. int.): 440 [M]’ (18), 411 [M-CHOJ’ (51). 5.02(lH,m,CH-6’),5.31(2H,2xt,CH-2’andCH-2’~625(lH,s, 232 (57). 207 (SO),202 (100). Acetylation with Ac,O in pyridine H-2), 6.95 (lH, s, H-5), 13.41 (1H. s,OH-1). MSm/z (rel. int.):494 yielded the corresponding 3@-acetate,identical in all respects with [Ml’ (96),479[M-Me]+ (11),476[M-H,O]+ (16),461(24X published data [ 173. 425 (lOOA407 (80), 383 (11). Methylation of 3 (10mg) by the method described above gave the trimethyl ether. ‘H NMR Rubraxamhone (1). Yellow prisms from petrol-EtOAc. (90 MHz CDCl,): 81.50, 1.50, 1.79, 1.89 (4 x C-Me), 3.50 (2H, mp 210” (lit. [a] 205-206”). Found: [MJ’ 410.1713; C,,H,,O, CH,-I’), 3.81, 3.88,3.95, 3.95 (4 x OMeA4.12 (2H, CH,-1’). 4.40 rquires 410.1729. UV j,$H nm: 242,253, 310, 348; (+ NaOH) 265, 296, 357; (+AlCl,) 260. 341, 390; (+NaOAc) 290, 354. (2H. 3”-CH,OH). 5.00 (lH, CH-6’). 5.27 (2H, CH-2’ and CH-2”). 6.57 (lH, H-2). 7.07 (IH, H-5). lRv_ cn-‘: 3450, 1655, 1610, 1580. ‘HNMR (2H) MHZ Xanthones from Garcinia Isolation o/ compounds from G. nmosa. CC of the coned extract over silica gel followed the same procedure as for G. pyrifera. From the eluate collected using 10 % EtOAc I(23 mg) was obtained and identified by comparison with material from G. pyrifera. Elution with 15 % EtOAc gave 8 as an impure brown solid which was then purified by circular prep. TLC on silica gel (solvent, toluene-EtOAc-AcOH; 70:30:3) to give a yield of 12mg. Neroosaxanthone (8). Amorphous. Found: [M]+ 464.2170; C28H3206 requires 464.2199. Wax nm: 230. 258, 283, 342. IR vaux cn-‘: 360@3100,1610,1580,1500. ‘H NMR (250 MHz. Me&O-d,): 6 1.52 (6H. s. I’-Me,X 1.66. 1.67,1.78,1.79 (4 x 3H, 4 x s, 3”-Me2. 3’“-Mez), 3.46 (2H, d, J = 6.4Hz., CH*-I”), 4.09 (2H, d, J = 6.1 Hz CH,-I”), 4.98 (lH, dd, J = 10.0, l.SHz, H-3’), 5.01 (lH, dd, J = 18.0, 1.5H2, H-3’), 5.10 (2H, m, CH-2 andCH-T”),6.3O(lH,dd.J= 18.O,lO.OHqH-YX722(lH,s,H-n 13.52 (lH, s, OH-l). MS m/z (rel. int.): 464 CM]’ (%), 449 (19). 396 (42). 393 (36). 381 (32). 367 (100). Acetylation of 8 with AC,0 in pyridine at 60” overnight followed by normal workup gave a mixture of compounds which were separated by circular prep. TLC over silica gel (solvent, toluene-EtOAc-AcOH, 19: 1:O.l). The major compound was identified as the 3.5,6triacetate; ‘H NMR (250 MHz, Me&O-d,): 61.51, 1.52, 1.66, 1.67. 1.77, 1.79 (6 x Me). 2.03.2.04.2.05 (3 x COMe), 3.40.4.19, (2 x CH,). 5.03 (2H) and 6.23 (H-3’ and H-2’). 7.49 (H-7). 13.62 (OH-l). The minor compound was identified as the 1,3,5,6tetraacetate; ‘H NMR (250 MH& Me,CO-d,): 61.43, 1.51, 1.65, 1167,1.75. 1.78 (6 x Me), 2.03, 2.04, 2.05, 2.06 (4 x COMe), 3.37, 4.00 (2 x CH,), 5.04, 5.10, 6.00 (H-3’ and H-2’) 7.69 (H-7). Isolalion ofcompoundsfrom G. polyantha. Identical treatment of extracts as above led to the elution of 10 (20 mg) from a silica gel column with 5% EtOAc. Further elution with 10% EtOAc yielded xanthochymol and 20% EtOAc gave isoxanthochymol. The benzophenones were both purified by circular prep. TLC using toluene-EtOAc-AcOH (90:9:1) as solvent, Anal yields being xanthochymol (300 mg) and isoxanthochymol (104 mg). Both compounds were confirmed by direct comparison with authentic samples [ 1I]. Isorheediaxanthone-B (10). Yellow clusters from petrol, mp 218’ (lit. [lS] 212-213”), [ab +25” (c 0.1; Me&O) (lit. [lS] + 16”). Found: [Ml’ 396.1561; C,,H,,O, requires 396.1573. UV, IR, MS in agreement with published data [IS]. ‘H NMR: see Table 2. Acetylation (method as for 8) gave a mixture of the diand triacetate. Separation of the former by circular prep. TLC (solvent; toluene_EtOAc-AcOH, 90:9: 1)gave the diaatateas an amorphoussolid, ‘H NMR: seeTable 2; W,IR,TLC identical to an authentic sample. authors thank Dr. G. Davison, Zoology Department, Universiti Kebangsaan Malaysia and Dr. D. W. AcknowledgementsThe 2355 Thomas, Missouri Botanic Gardens, for the collection of plant material. Professor F. Delle Monache is acknowledged for the supply of rheediaxanthoneB and isorheediaxanthone-B diacetate reference samples. One of us (S. A. A.) wishes to thank the Association of Commonwealth Universities for the award of a scholarship. REFERENCES 1. Willis, J. C. (1973) A Dic~ionuryojFlowering Plants and Ferns (revised by H. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQP K . Airy Shaw) 8th edn. Cambridge University Press, Cambridge. 2. Waterman, P. G. and Husaain, R. A. (1983) B&hem. Syst. Ecol. 11, 21. 3. Comer, E. J. H. 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