Natural products from Malaysian rainforests

Plants have played an important role in the ancient culture of India, China and Egypt as medicine. Plants have been and always will be an important source of new drugs and new drug leads. Drug discovery based on plants have resulted in the development of anticancer agents and continues to contribute to new leads in clinical trials. The discovery of Cinchona in the 17th century, followed by Digitalis, morphine and then the introduction of synthetic aspirin, a derivative of a plant-based drug, have led human beings to believe in the many wonders of the wealth of the forests. Natural products have provided challenging synthetic targets and their biological activity has given leads for the development of valuable medicines. Screening programmes exist for bioactive compounds and these have led to new drugs, example: taxol - which is used for the treatment of various cancers. Natural products also play a role in ecology by regulating the interactions between plants, microorganisms, insects, and animals. These can be defensive substances, anti feedants, attractants, and pheromones. Chemotaxonomy is another reason for scientists to study natural products. Chemotaxonomy involves the use of natural products in the classification of species, e.g. alkaloids are typically present in the Annonaceae family especially in Kopsiaspecies, or xanthones are typically present in Garciniaspecies while coumarins are typical of Calophyllumspecies. Phytochemical surveys can also reveal natural products that are markers for botanical and evolutionary relationships. The study of natural products have resulted in modern techniques for separation, structural elucidation, screening and combinatorial synthesis have led to increased interest in plant natural products as sources of new drugs. The introduction of herbal products in the form of nutraceuticals and dietary supplements are also changing the plant-based drug market

Secondary metabolites from two garcinia species and their biological activities.

Detail chemical studies on Garcinia maingayi have yielded one xanthone, 1,3,7-trihydroxy-2-(3-methylbut-2-enyl)xanthone, one benzophenone, isoxanthochymol, one benzoic acid derivative 3,4-dihydroxy-methylbenzoate and two triterpenoids, stigmasterol and sitosterol. Meanwhile, investigations on Garcinia parvifolia have afforded one triterpenoid, α-amyrin and two xanthones, cowanin and rubraxanthone. Their structures were derived based on spectroscopic evidence, mainly 1D and 2D NMR spectroscopy. Acetylation reaction was carried out on rubraxanthone to yield triacetate rubraxanthone. It was found that the pure rubraxanthone was strongly active against the larvae of Aedes aegypti with LC50 value of 15.49 μg/mL and HL-60 cell line with an IC50 value of 7.5 μg/mL

Anthraquinones and Xanthones from Cratoxylum glaucum (Guttiferae)

In a continuing search for xanthones and quinones from the Guttifere family, we decided to look at the genus Crotoxylum. A detailed chemical study on Cratoxylum glaucum has led to the isolation of two triterpenoids, friedelin (1) and stigmasterol 9(2), two anthraquinones 1,8-dihydroxy-6-menthoxyanthraquinone (3) and vismiaquinone (4) and one xanthone dimenthymangostin (5). These compounds were identified using the 1D and 2D NMR spectroscopy. This is the first report done on the chemistry of Cratoxylum glaucum

Alpha-mangostin and beta-mangostin from Cratoxylum laucum.

Our continuing interest in xanthones and anthraquinones from the Cratoxylum genus has led us to look at Cratoxylum glaucum. This resulted in the isolation of alpha-mangostin (1), beta-mangostin (2), fuscaxanthone C (3), 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone (4), beta-sitosterol (5), 1,8-dihydroxy-3-methoxy-6-methylanthraquinone (6), stigmasterol (7), friedelin (8) and betulinic acid (9). Structural elucidations of these compounds were achieved by using ID and 2D NMR spectroscopic experiments. Cytotoxic assays indicated that the hexane and ethyl acetate extracts demonstrated cytotoxicity against the MCF7 cancer cell line. Meanwhile, the ethyl acetate and methanol extracts of C. glaucum inhibited the HL-60 cancer cell line activity

Chemistry and cytotoxic activity of essential oil from the stem bark of Calophyllum soulattri

GCMS analysis of the essential oil from the stem bark of Calophyllum soulattri detected twenty components. Allo-aromadendrene was present as the most abundant component. Two other major constituents are α-gurjunene and β-eudesmene. The volatile oil exhibited moderate cytotoxicity against SNU-1, Hep G2, NCI-H23, K562, Raji, IMR-32 and SK-MEL-28 cells

Garcinia mangostana: a source of potential anti-cancer lead compounds against CEM-SS cell line

Our current interest in searching for natural anti-cancer lead compounds from plants has led us to the discovery that the stem and roots of Garcinia mangostana can be a source of such compounds. The stem furnished 2,8-dihydroxy-6-methoxy-5-(3-methylbut-2-enyl)-xanthone (1), which is a new xanthone. Meanwhile, the root bark of the plant furnished six xanthones, namely -mangostin (2), β-mangostin (3), γ-mangostin (4), garcinone D (5), mangostanol (6), and gartanin (7). The hexane and chloroform extracts of the root bark of G. mangostana as well as the hexane extract of the stem bark were found to be active against the CEM-SS cell line. γ-Mangostin (4) showed good activity with a very low IC50 value of 4.7 μg/ml, while -mangostin (2), mangostanol (6), and garcinone D (5) showed significant activities with IC50 values of 5.5, 9.6, and 3.2 μg/ml, respectively. This is the first report on the cytotoxicity of the extracts of the stem and root bark of G. mangostana and of -mangostin, mangostanol, and garcinone D against the CEM-SS cell line

Comparison of nutrient composition in kernel of tenera and clonal materials of oil palm (Elaeis guineensis Jacq.).

Nutritive information about oil palm kernel is scarce, especially on the composition of sugars and water-soluble vitamins. This study aims to evaluate both tenera and clonal materials for their proximate composition, fatty acid profile, amino acid composition, sugar, mineral and water-soluble vitamin contents. The tenera material had a higher moisture, fat and fibre content as compared to the clonal material, whereas protein, carbohydrate and ash content were higher in the clonal material. The major fatty acid constituents in palm kernel oil were lauric acid, myristic acid and oleic acid. The palm kernel proteins were deficient in lysine and tryptophan but rich in glutamic acid, arginine and aspartic acid. Sucrose was the most abundant sugar in palm kernel. The mineral analysis of the samples showed high levels of potassium, phosphorus, magnesium, calcium and manganese, while niacin was the water-soluble vitamin present at the highest concentrations in palm kernel

Cytotoxic and antioxidant properties of Borneo Garcinia species (Clusiaceae)

There are several local Malaysian Garcinia species which have ethnobotanical uses but so far very few studies have been carried out to link these folkloric uses with the phytochemistry of these plant species. It would be interesting therefore, to develop phytochemical data of two such Sarawakian species which are Garcinia eugenifolia and Garcinia nitida which have not been reported before. The methanol extract from the G. eugenifolia leaves exhibited moderate antioxidant activity with EC50 values of 66 and 51 respectively, when compared to ascorbic acid with EC50 values of 15.32 μg/mL. This crude also showed weak cytotoxic activity to HeLa with IC50 values of 71 and 40 μg/mL respectively. However, the leaves extracts of G. nitida showed good cytotoxic activity with IC50 values of 4 and 7 μg/mL respectively towards both cell lines

Xanthone from Garcinia eugenifolia (Clusiaceae)

Studies on the twigs of Garcinia eugenifolia have led to the isolation of one xanthone 5,9-dihydroxy-8-methoxy-2,2-dimethyl-7-(3-methylbut-2-enyl)pyrano[3,2-b]xanthen-6(2H)-one (1) and one triterpenoid, sitosterol (2). Meanwhile, studies on the leaves of Garcinia eugenifolia provided another triterpenoid, friedelin (3). The structures of these compounds were determined by spectroscopic methods such as 1H NMR, 13C NMR, mass spectrometry (MS) and by comparison with previous studies. The hexane and ethyl acetate extracts of Garcinia eugenifolia indicated strong cytotoxicity towards the HL-60 cell line with IC50 values of 1.9 μg/ml and 2.5 μg/ml respectively. However, the methanol extract gave moderate inhibitory activities (IC50<10 μg/ml) towards HL-60 cell line

Xanthones from Calophyllum inophyllum

Repeated separation and purification of fractions from the crude chloroform extract of Calophyllum inophyllum via column chromatography afforded five known xanthone caloxanthones A, B, C, macluraxanthone and pyranojacareubin. Structural elucidations and determination of the isolated compounds were supported by spectral analyses obtained by subjecting the compounds to various spectroscopic techniques. The chloroform extract, when tested against RAW264.7 cells for anti-inflammatory potentials, exhibited the most promising activity with an IC50 value of 14.81±0.04 µg/mL compared to moderate activities shown by the ethyl acetate and n-hexane extracts. Antimicrobial tests showed that the n-hexane and chloroform extracts acted moderately against Staphylococcus epidermidis S273 and Bacillus subtilis B145