Studies have been undertaken to investigate the effect of sugars on the thermal and rheological properties of sago starch. Sugars were found to increase the gelatinization temperature T(gel), and gelatinization enthalpy DeltaH. T(gel) and DeltaH increased in the following order: control (water alone) < ribose < fructose < glucose < maltose < sucrose. The increase in DeltaH was greater for 50% starch compared to 10% starch samples. The swelling factors in the presence of sugar were higher compared to the control for sugar concentrations below 25% but were lower at sugar concentration greater than 25%. These effects are discussed in terms of the antiplaticizing effect of the sugars compared to water, the influence of sugar-starch interactions and also the effect of the sugars on water structure. The storage modulus G', the rate constant of gelation k, and the gel strength were significantly reduced in the presence of sugars. Generally G' and k decreased in the following order: control (water alone) > hexose > disaccharide > pentoses. This has been attributed to the reduced proportion of amylose leached following gelatinizatison. In the presence of hexoses the freeze-thaw stability of starch gels decreased while in the presence of disaccharides and pentoses the freeze-thaw stability was slightly improved.
Eleven compounds: goniomicin A (1), goniomicin B (2), goniomicin C (3), goniomicin D (4), tapisoidin (5), goniothalamin (6), 9-deoxygoniopypyrone (7), pterodondiol (8), liriodenine (9), benzamide (10) and cinnamic acid (11), were isolated from the stem bark of Goniothalamus tapisoides. All compounds were identified by spectroscopic analysis and, for known compounds, by comparison with published data. Goniothalamin (6) exhibited mild cytotoxic activity towards a colon cancer cell line (HT-29), with an IC50 value of 64.17 ± 5.60 µM. Goniomicin B (2) give the highest antioxidant activity in the DPPH assay among all compounds tested, with an IC50 of 0.207 µM.
Nine essential oils, hydrodistilled from different parts of five Goniothalamus species (G. velutinus Airy-Shaw, G. woodii Merr., G. clemensii Ban, G. tapis Miq. and G. tapisoides Mat Salleh) were evaluated for their ability to inhibit platelet aggregation in human whole blood using an electrical impedance method and their inhibitory effects on platelet activating factor (PAF) receptor binding with rabbit platelets using 3H-PAF as a ligand. The chemical composition of the oils was analyzed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). The bark oil of G. velutinus was the most effective sample as it inhibited both arachidonic acid (AA) and ADP-induced platelet aggregation with IC50 values of 93.6 and 87.7 µg/mL, respectively. Among the studied oils, the bark oils of G. clemensii, G. woodii, G. velutinus and the root oil of G. tapis showed significant inhibitory effects on PAF receptor binding, with IC50 values ranging from 3.5 to 10.5 µg/mL. The strong PAF antagonistic activity of the active oils is related to their high contents of sesquiterpenes and sesquiterpenoids, and the individual components in the oils could possibly produce a synergistic effect in the overall antiplatelet activity of the oils.
The essential oils from different parts of Litsea cubeba, collected from the highlands of Sarawak, were isolated and their chemical compositions analyzed. This study demonstrated significant variations in the chemical compositions and the chemical profiles of the volatiles and could provide valuable supplementary information on the geographical variations of the species. The fruit essential oil was dominated by citronellal, d-limonene and citronellol, while the leaf oil was high in eucalyptol and α-terpineol. High concentrations of citronellal and citronellol in both the root and bark oils were identified. In the stem, the oil was dominated by eucalyptol, d-limonene and α-terpineol. The activity of the oils against brine shrimp larvae, bacteria, yeast and fungi was determined. The oils were toxic against brine shrimp larvae with LC 50 values ranging from 25.1-30.9 μL/mL. The oils also demonstrated a wide spectrum of inhibition against microorganisms with inhibition zones between 19.5-46.7 mm against Gram-positive bacteria and 10.5-90.0 mm against yeast and fungi. However, the oils were not active against Gram-negative bacteria.
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