Wan Ahmad

Dereplication of Saccharide and Polyol Constituents of Candidate Sweet‐tasting Plants: Isolation of the Sesquiterpene Glycoside Mukurozioside IIb as a Sweet Principle of Sapindus rarak

In the search for new potently sweet compounds from plants, the rapid identification and quantification of free sugars and polyols in a crude plant extract is important for dereplication purposes, wherein compounds of known structure or biological activity are removed from further consideration. Accordingly, plants found to have high levels of free sugars and polyols are regarded as lower priority leads when screening for novel natural sweeteners. In the present study, gas chromatography–mass spectrometry was used to examine the sugar/polyol content of six sweet-tasting species, comprised of the pericarp of Dialium indum L. (Leguminosae), the stem of Drypetes floribunda Hutchinson (Euphorbiaceae), the fruit of Hymenaea oblongifolia Huber var. palustris (Ducke) Lee and Langenheim (Leguminosae), the rhizomes of Imperata cylindrica (L.) Beauvois (Gramineae), the fruit of Manilkara zapota (L.) van Royen (Sapotaceae), and the pericarp of Sapindus rarak DC. (Sapindaceae). The total yields of sugars/polyols in these plant parts were 1.9, 6.1, 7.8, 4.5, 10.8 and 2.9% w/w, respectively. Several uncommon polyols were identified, including bornesitol in D. floribunda and quebrachitol in S. rarak. It is likely that the sweet taste of the plants containing more than 5% of sugars/polyols is imparted as a result of the high free sugar and/or polyol content. Owing to its low level of free sugars, S. rarak pericarp was chosen for further study, and the known sesquiterpene glycoside mukurozioside IIb (1) was isolated in high yield (6.3% w/w) as a sweet-tasting constituent. Preliminary evaluations, comprised of mouse acute toxicity and bacterial mutagenesis determinations, indicated the safety of 1. The compound was subsequently rated by a human taste panel as having about the same sweetness potency as sucrose.

Transformation of crystalline starch nanoparticles into highly luminescent carbon nanodots: Toxicity studies and their applications

Being abundant in many tropical part of the world, Dioscorea sp. as food is limited due to its toxicity. However polysaccharides derive from these tubers could be important for other applications. Here we developed a Highly Luminescent Carbon Nanodots (C-dots) via acid hydrolysis of Gadong starch (GS). The hydrolysis rate of GS increased from 49% to 86% within 7 days while the X-ray diffraction showed the native GS particle is a C-crystalline type. The GS particles were either round or oval with diameters ranging from 50-90 nm. Further acid dehydration and surface oxidation reduced the size of GS nanoparticles to 6-25 nm. The C-dots produced a fluorescent emission at wavelength 441 nm. Toxicity tests demonstrate that zebrafish embryo were able to tolerate the C-dots for 48 h after exposure. This study has successfully demonstrated a novel approach of converting GS into excellent fluorescent C-dot.

Crystal structure of 3-(2-amino-1,3-selenazol-4-yl)-2H-chromen-2-one - Dimethylformamide (1/1), C15H15N3O3Se

Abstract C15H15N3O3Se, triclinic, P1̅ (no. 2), a = 9.5686(7) Å, b = 12.3795(9) Å, c = 14.7854(11) Å, α = 93.844(2)°, β = 106.344(2)°, γ = 110.816(2)°, V = 1543.4(2) Å3, Z = 4, Rgt(F) = 0.0489, wRref(F2) = 0.1066, T = 300 K.

Preparation and characterization of polymeric nanoparticles from Gadong starch

Dioscorea hispida (Gadong tuber) was seldom used and forgotten as a food source due to their toxicity. In contrast to that, the Gadong tuber can be a source of polysaccharides which can be manipulated as an alternative source for industrial applications. This research reported on how to synthesize starch nanoparticles from Gadong tuber by using a simple acid hydrolysis process. The yield of starch nanoparticles obtained from seven days of acid hydrolysis was reduced to 13%. The X-ray diffraction measurements showed that the native Gadong starch particle is of the C-crystalline type, and that the synthesized nanoparticles showed an increase in crystallinity compared to the native particles. Transmission electron microscopy results demonstrated that the starch particle morphologies were either round or irregular shape, with diameters ranging from 96-110u2005nm.

COD and color removal of reactive orange 16 dye solution by electrochemical oxidation and adsorption method

Degradation of Reactive Orange 16 (RO16) dye was investigated using electrochemical oxidation and adsorption (batch method) using mixture of coconut trunk charcoal-graphite-tin-polyvinyl chloride(PVC). In batch studies for adsorbents pellet and powder form of the charcoal mixture were used. RO16 was chosen as the model dye because of its high resistance towards conventional treatment methods. NaCl and RO16 concentration, treatment duration, weight of electrode and adsorbent and volume of solution were kept constant for both methods. The effectiveness of the treatments were compared and evaluated by percentage of RO16 decolorization and chemical oxygen demand (COD) removal and results indicated that electrochemical oxidation method ables to decolorized RO16 dye up to 98.5% after 20 minutes electrolysis time while pellet and powder in batch method only removed 17.1 and 33.6% of RO16 color respectively. However, only 45.6% of COD can be removed using electrochemical oxidation method while pellet and powder i...