Ghalib Said Al-Saidi

Thermal characterisation of gelatin extracted from yellowfin tuna skin and commercial mammalian gelatin.

Glass transition and other thermal characteristics of gelatin from different sources were studied by differential scanning calorimetry (DSC) and modulated DSC (MDSC). The initial glass transition temperatures of equilibrated gelatin samples at 11.3% relative humidity, determined from reversible heat flow thermogram of MDSC, were 23, 75 and 59°C, respectively, for tuna skin, bovine and porcine gelatin. When gelatin samples were equilibrated at higher relative humidity of 52.9%, glass transition temperature of fish skin and bovine gelatin decreased to -3 and 57°C, respectively. Further increase of equilibration relative humidity to 75.3% showed increased value in the case of tuna skin, whereas bovine and porcine did not show any significant change. DSC and MDSC results indicated that tuna gelatin showed lower glass transition compared to mammalian source gelatin equilibrated at the same constant relative humidity. In general glass transition measured by DSC was found lower than the values measured by MDSC. The results in this study showed that the degree of plasticization varied with the source of gelatin as well as their extraction methods.

Papaya epicarp extract protects against hydrogen peroxide-induced oxidative stress in human SH-SY5Y neuronal cells.

Recent studies indicated that regular consumption of antioxidant-rich foods reduces cellular oxidative stress and protects against health-related problems. This study aimed to assess the in vitro antioxidant properties of the papaya epicarp extract against hydrogen peroxide (H2O2)-induced oxidative stress in human SH-SY5Y neuronal cells. Our study revealed that papaya epicarp extract acted as a potent free radical scavenger and provided neuroprotection against H2O2-induced oxidative stress. Papaya epicarp extract ameliorated glutathione depletion, restored total antioxidant capacity and augmented the inhibition of antioxidant enzymes (catalase, glutathione peroxidases and superoxide dismutase). In conclusion, papaya epicarp extract can be used as a functional dietary ingredient that might help in reducing the neurological health problems associated with various oxidative stress insults.

Thermal Relaxation of Gelatin and Date Flesh Measured by Isothermal Condition in Differential Scanning Calorimetry (DSC) and its Relation to the Structural and Mechanical Glass Transition

A new innovative method was developed to measure the thermal-relaxation by maintaining isothermal condition in a Differential Scanning Calorimetry (DSC). The DSC thermal-relaxation characteristics of gelatin and date flesh were found to be related with the structural- and mechanical-glass transition measured by conventional DSC linear-heating and thermal-mechanical analysis (i.e, Differential Thermal Mechanical Analysis, DMTA). Initial slope of the thermal relaxation curve (i.e., heat flow versus relaxation time) was determined and it was plotted as a function of relaxation temperature (i.e., isothermal condition). The initial slope-temperature graph showed three thermal relaxation characteristics: limited mobile, freely mobile and restricted mobile regions. The region 1 showed limited molecular mobility with increasing temperature, while region 2 showed free mobility with increasing temperature sensitivity. The intersection of the regions 1 and 2 was related to the structural-glass transition measured by conventional linear-heating in a DSC. The region 3 showed restricted mobility due to enhanced interactions of the phases at higher temperature. This region 3 was related to the entangled flow region measured by thermal-mechanical analysis in a DMTA.

Synthesis and Characterization of bis[n-(4-benzoyloxy) Benzylidene{n(n-di-/tri-alkoxy)benzoyl}-hydrazinato]nickel(II) Complexes Displaying Liquid Crystalline Columnar Phases

A series of materials based on the aroylhydrazinatonickel (II) complex is synthesized and characterized. The molecule in the materials consist of two 4-benzoyloxy-benzene groups and two benzene rings having two or three alkoxy chains containing 6, 8, 10, and 12 carbon atoms attached at the azomethine moiety. The synthesis, characterization by NMR and the phase sequence observed by DSC and polarized light microscopy are presented. Most of the compounds in the series display columnar phases in the temperature range between 100°C and 200°C. The phases observed and their temperature ranges are discussed in terms of the number and position of attached alkoxy chains.