Alkaloids and carboxylic acids from Piper nigrum

Detailed chemical studies were carried out on the roots of Piper nigrum. Six alkaloids and four carboxylic acids were isolated and identified from this study. The alkaloids were piperolactam A (1), piperolactam D (2), cepharadione A (3), piperine (4), sylvamide (5) and 2,4-tetradecadienoic acid isobutyl amide (6). The carboxylic acids were tetracosanoic acid, p-hydroxy-m-methoxycinnamate ester (7), 3,4-methylenedioxycinnamic acid (8), 2-butenedioic acid, mono-(2-methylpropyl) ester (9) and 3,4-methylenedioxy benzoic acid (10). Larvicidal assays on Aedes aegypti were carried out on the crude extracts of these plants as well as the pure compounds. The larvae were found to be susceptible to some of these extracts and compounds. This paper reports the isolation and characterization of these compounds as well as bioassay data. This is the first report on the presence of piperolactam A (1), piperolactam D (2) cepharadione A (3) and sylvamide (5) in Piper nigrum

Alkaloids from Piper nigrum and Piper betle

An investigation, on the roots of Piper nigrum and the aerial parts of Piper betle, has yielded several alkaloids. The dried root sample of Piper nigrum was extracted using various solvents in increasing polarity. The dried aerial part of Piper betle was extracted using the Soxhlet extraction method. The alkaloids isolated were pellitorine(1), (E)-1-[3',4'- (Methylenedioxy)cinnamoyl]piperidine(2), piperine(3), piperolactam D(4), cepharadione A(5), and 2,4-tetradecadienoic acid isobutyl amide(6). These compounds were isolated using chromatographic methods, while the elucidation of the structures was carried out using MS, IR and NMR techniques. The extracts of Piper nigrum and Piper betle were also tested for cytotoxicity activities. This is the first report on (E)-1-[3',4'-(Methylenedioxy)cinnamoyl] piperidine(2) from Piper nigrum as a natural product

Cytotoxicity and structure-activity relationships of xanthone derivatives from Mesua beccariana, Mesua ferrea and Mesua congestiflora towards nine human cancer cell lines.

The cytotoxic structure-activity relationships among a series of xanthone derivatives from Mesua beccariana, Mesua ferrea and Mesua congestiflora were studied. Eleven xanthone derivatives identified as mesuarianone (1), mesuasinone (2), mesuaferrin A (3), mesuaferrin B (4), mesuaferrin C (5), 6-deoxyjacareubin (6), caloxanthone C (7), macluraxanthone (8), 1,5-dihydroxyxanthone (9), tovopyrifolin C (10) and α-mangostin (11) were isolated from the three Mesua species. The human cancer cell lines tested were Raji, SNU-1, K562, LS-174T, SK-MEL-28, IMR-32, HeLa, Hep G2 and NCI-H23. Mesuaferrin A (3), macluraxanthone (8) and α-mangostin (11) showed strong cytotoxicities as they possess significant inhibitory effects against all the cell lines. The structure-activity relationship (SAR) study revealed that the diprenyl, dipyrano and prenylated pyrano substituent groups of the xanthone derivatives contributed towards the cytotoxicities

Resource annotation framework in a georeferenced and geospatial digital library

SingAREN 2

Cratoxylum glaucum and cratoxylum arborescens (Guttiferae)-two potential source of antioxidant agents.

Our detailed chemical studies on Cratoxylum glaucum and C. arborescens have revealed the presence of 5-demethoxycadensin G (1), fuscaxanthone C (2), b-mangostin (3), 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone (4), vismiaquinone (5), 1,8-dihydroxy-3-methoxy-6-methylanthraquinone (6), stigmasterol (7) and friedelin (8). Structural elucidations of these compounds were achieved by using 1D and 2D NMR spectroscopic experiments. Antioxidant tests conducted on these two plant species gave promising results with both species indicating good antioxidant inhibiting properties. This is a first report on 5-demethoxycadensin G (1) and b-mangostin (3) from Cratoxylum glaucum as well as the antioxidant properties of these two species

A digital library for geography examination resources

We describe a Web-based application developed above a digital library of geographical resources for Singapore students preparing to take a national examination in geography. The application provides an interactive, non-sequential approach to learning that supplements textbooks.Published versio

A new cytotoxic carbazole alkaloid isolated from the stem bark of Malaysian Clausena excavata

Malaysia is one of the richest in its biodiversity in the world. There are not less than 12,000 plants species in its rain forest. The aim of this study is a continuous investigation for medicinal plants in Malaysia, especially the chemical constituents that are poses significant activities, i.e. anti-cancer. Clausena excavata (Rutaceae) has been known as a very rich in carbazole alkaloids, coumarins and limonoids species. In the present study, one new carbazole alkaloid, 1,8-dihydroxy-3-formyl-4- prenylcarbazole (Clausine–TH), and two other known compounds, Clausenarin (coumarin) and Clausine–K (carbazole alkaloid), were isolated from the methanol extract of the stem bark of Clausena excavata, collected from Kedah, Malaysia. Structures of these compounds were confirmed by various spectroscopic analyses including GC-MS, NMRs, and FTIR. All pure compounds isolated were tested for their cytotoxicity against CEM-SS cell lines, with the Clausine–TH and Clausine–K gave a very strong activity with an IC50 value of 2.1 µg/mL and 5.1 µg/mL, respectively

On assigning place names to geography related web pages

In this paper, we attempt to give spatial semantics to web pages by assigning them place names. The entire assignment task is divided into three sub-problems, namely place name extraction, place name disambiguation and place name assignment. We propose our approaches to address these sub-problems. In particular, we have modified GATE, a wellknown named entity extraction software, to perform place name extraction using a US Census gazetteer. A rule-based place name disambiguation method and a place name assignment method capable of assigning place names to web page segments have also been proposed. We have evaluated our proposed disambiguation and assignment methods on a web page collection referenced by the DLESE metadata collection. The results returned by our methods are compared with manually disambiguated place names and place name assignment. It is shown that our proposed place name disambiguation method works well for geo/geo ambiguities. The preliminary results of our place name assignment method indicate promising results given the existence of geo/non-geo ambiguities among place names.Published versio

Aesthetic Experience and Acceptance of Human Computation Games

Human computation games (HCGs) are applications that leverage games to solve computational problems that are out reach of the capacity of computers. Game aesthetics are critical for HCG acceptance, and the game elements should motivate users to contribute time and effort. In this paper, we examine the effect of aesthetic experience on intention to use HCGs. A between-subjects experiment was conducted to compare a HCG and a human computation system (HCS). Results demonstrated that HCGs provided a greater sense of aesthetic experience and attracted more intentional usage than HCSs. Implications of this study are discussed.Accepted versio