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Abstract:In a preliminary antiprotozoal screening of several Clusiaceae species, the methanolic extracts of Allanblackia monticola and Symphonia globulifera showed high in vitro leishmanicidal activity. Further bioguided phytochemical investigation led to the Molecules 2007, 12 1549 isolation of four benzophenones: guttiferone A (1), garcinol (2), cambogin (3) and guttiferone F (4), along with three xanthones: allanxanthone A (5), xanthone V 1 (6) and globulixanthone C (7) as active constituents. Compounds 1 and 6 were isolated from S. globulifera leaves, while compounds 2-5 were obtained from A. monticola fruits. Guttiferone A (1) and F (4) showed particulary strong leishmanicidal activity in vitro, with IC 50 values (0.2 µM and 0.16 µM, respectively) comparable to that of the reference compound, miltefosine (0.46 µM). Although the leishmanicidal activity is promising, the cytotoxicity profile of these compounds prevent at this state further in vivo biological evaluation. In addition, all the isolated compounds were tested in vitro for their anticholinesterase properties. The four benzophenones showed potent anticholinesterase properties towards acetylcholinesterase (AChE) and butylcholinesterase (AChE). For AChE, the IC 50 value (0.66 µM) of garcinol (2) was almost equal to that of the reference compound galanthamine (0.50 µM). Furthermore, guttiferone A (1) and guttiferone F (4) (IC 50 = 2.77 and 3.50 µM, respectively) were more active than galanthamine (IC 50 = 8.5) against BChE.

The aim of this study was to determine the in vitro antioxidant activity, free radical scavenging property and the beneficial effects of extracts of various parts of Syzygium guineense in reducing oxidative stress damage in the liver. The effects of extracts on free radicals were determined on radicals DPPH, ABTS, NO and OH followed by the antioxidant properties using Ferric Reducing Antioxidant Power assay (FRAP) and hosphomolybdenum (PPMB). The phytochemical screening of these extracts was performed by determination of the phenolic content. The oxidative damage inhibition in the liver was determined by measuring malondialdehyde (MDA) as well as the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase. Overall, the bark extract of the ethanol/water or methanol showed the highest radical scavenging activities against DPPH, ABTS and OH radicals compared to the other extracts. This extract also contained the highest phenolic content implying the potential contribution of phenolic compounds towards the antioxidant activities. However, the methanol extract of the root demonstrated the highest protective effects of SOD and CAT against ferric chloride while the hydro-ethanol extract of the leaves exhibited the highest inhibitory effects on lipid peroxidation. These findings suggest that antioxidant properties of S. guineense extracts could be attributed to phenolic compounds revealed by phytochemical studies. Thus, the present results indicate clearly that the extracts of S. guineense possess antioxidant properties and could serve as free radical inhibitors or scavengers, acting possibly as primary antioxidants. The antioxidant properties of the bark extract may thus sustain its various biological activities.

Six new unusual C-4'-prenylated flavonols, dorsilurins F-K (1-6), together with six known compounds were isolated from the roots of Dorstenia psilurus, and their structures were elucidated on the basis of spectroscopic evidence. The isolated compounds exhibited moderate to low alpha-glucosidase inhibitory activity. Dorsilurin F (1), with three unmodified prenyl groups, was the most active, while dorsilurin K (6), with only one unmodified prenyl group, was the least active compound. Furthermore, NMR data of dorsilurin C (7), isolated some years ago from the same plant, have been revised.

Elephantopus mollis KUNTH, belonging to the Asteraceae, is used in Cameroon for the treatment of cancer, fracture, abdominal pains, defective lactation and snake bite.1) In our continuing search for novel bioactive compounds from Cameroon medicinal plants, we have previously isolated sesquiterpene lactones with cytotoxic activities.2) Sesquiterpene lactones have been isolated from numerous genera of the Asteraceae family and are described as the active constituents of a variety of medicinal plants used in traditional medicine.3-7) Because of an interest in cytotoxic sesquiterpene lactones, the methanol extract of roots and stems of E. mollis was re-examined and three new cytotoxic sesquiterpene lactones, namely, (4bH)-5a-hydroxy-8a-(2-methylbut-2-enoyloxy)-2-oxo-1(10),11(13)-guaiadien-12,6a -olide ( 1 ) , ( 4 b H ) -8 a -( 2 -m e t hy l b u t -2 -e n oy l ox y ) -2 -ox o -1(5),10(14),11(13)-guaiatrien-12,6a -olide (2) and 2,5-epoxy-2b -hydroxy-4a -methoxy-8a -(2-methylbut-2-enoyloxy)-4(15),10(14),11(13)-germacratrien-12,6a -olide (3) were isolated, together with 2b-methoxy-2-deethoxyphantomolin (4),8) molephantin and molephantinin.2)These compounds were evaluated for their cytotoxic activities against neuroblastoma B104. Results and DiscussionThe chloroform extract, which was obtained from methanol extract of the whole bodies of E. mollis, was subjected to repeated column chromatography followed by preparative thin-layer chromatography (TLC) to give three new (1-3) and two known (4, 5) compounds.Compound 1 The connectivity from H-6 to H-9 was confirmed by COSY spectroscopy. Analysis of 2D NMR data (COSY, heteronuclear single quantum correlation (HSQC), HMBC) led to the complete assignment of NMR signals. HMBC correlations of H 3 -15 to C-3, C-4 and C-5 and from H 3 -14 to C-1, C-9, and C-10 revealed that Me-14 and Me-15 are attached to C-10 and C-4, respectively. Further HMBC correlations were observed between H 2 -3 and C-1, C-2, C-4 and C-5 and suggested that compound 1 is a guaiane-type sesquiterpene. The configuration at C-4, C-5, C-6, C-7, and C-8 was determined by NOESY (correlations between H-4 and H-6, H-6 and H-8, H-7 and H-9a were observed) and by comparison of coupling constants with those of naturally occurring germacranolide and guaiane-type sesquiterpenes. [10][11][12] Further confirmation of the structure was made by comparison of data with those of (4bH)-5a-hydroxy-8a-(2-methylpropenoyloxy)-1(10),11(13)-guaiadien-12,6a-olide.3) The relative configuration of the 2-methylbut-2-enoyloxy residue was deduced from coupling constants (Table 1) and by NOE data obtained from NOESY spectrum (Fig. 1).Compound 2 was shown to have the molecular formula ). The 1 H-and 13 C-NMR data (Table 1) were similar to those of 1 with a ketone carbonyl, an a-methylene-gbutyrolactone and a 2-methylbut-2-enoyloxy moiety. However, the quaternary oxygenated carbon observed in compound 1 is replaced by an exomethylene group [d H 5.24, 5.75; d C 122.2 (CH 2 ), 133.5 (C)]. Since an olefin carbon [d C 174.6 (C)] was shifted do...

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Three new prenylated anthranoids, harunmadagascarins C (1) and D (2) and kenganthranol D (3), together with three known compounds (4-6) were isolated from the leaves of Harungana madagascariensis. Their structures were assigned by spectroscopic methods and by comparison with literature data. In the three new natural products 1-3, one or two prenyl groups are incorporated in furan, pyran, or cyclohexane rings in four different modes of annulation. Compounds 2, 4, and 6 were strongly active against the Gram-positive Bacillus megaterium.