Yeşim Yeşiloğlu

Antioxidant properties of various solvent extracts from purple basil

Water, ethanol and acetone extracts from leaves and flowers of purple basil, one of the most popular spices consumed in the Thrace region of Turkey, were tested in vitro for their ability to inhibit peroxidation of lipids, to scavenge DPPH, hydrogen peroxide, superoxide anion, to reduce Fe(III) to Fe(II) and to chelate Fe(II) ions. The results showed that purple basil contained naturally occurring antioxidant components and possessed antioxidant activity which may be attributed to its lipid peroxidation inhibitory, radical scavenging and metal chelating activities. It was concluded that purple basil might be a potential source of antioxidants.

Partial Purification and Characterization of Almond Seed Lipase

Abstract A lipase was partially purified from the almond (Amygdalus communis L.) seed by ammonium sulfate fractionation and dialysis. Kinetics of the enzyme activity versus substrate concentration showed typical lipase behavior, with Km and Vmax values of 25 mM and 113.63 µmol min−1 mg−1 for tributyrin as substrate. All triglycerides were efficiently hydrolyzed by the enzyme. The partially purified almond seed lipase (ASL) was stable in the pH range of 6–9.5, with an optimum pH of 8.5. The enzyme was stable between 20 and 90°C, beyond which it lost activity progresively, and exhibited an optimum temperature for the hydrolysis of soy bean oil at 65°C. Based on the temperature activity data, the activation energy for the hydrolysis of soy bean oil was calculated as −5473.6 cal/mol. Soy bean oil served as good substrate for the enzyme and hydrolytic activity was enhanced by Ca2+, Fe2+, Mn2+, Co2+, and Ba2+, but strongly inhibited by Mg2+, Cu2+, and Ni2+. The detergents, sodiumdeoxicholate and Triton X-100 strongly stimulated enzyme activity while CTAB, DTAB, and SDS were inhibitors. Triton X-405 had no effect on lipase activity. The partially purified enzyme retained its activity for more than 6 months at −20°C, beyond which it lost activity progressively.

Polyvinyl Alcohol–Trypsin as a Catalyst for Amino Acid Ester Synthesis in Organic Media

Abstract The bovine trypsin‐catalyzed synthesis of N‐α‐benzoyl‐DL‐arginine esters from N‐benzoyl‐DL‐arginine were studied in various organic solvents. Trypsin was immobilized to polyvinyl alcohol (PVA) by adsorption from its aqueous solutions. Immobilized enzyme showed higher catalytic activities than free enzyme for amino acid esterification in ethanol. The yield of ester is strongly dependent upon the PVA/trypsin ratio and water content in the reaction medium. The rate and equilibrium constant of the ester formation reaction are also dependent on water content.

Biochemical Properties of Free and Immobilized Candida rugosa Lipase onto Al2O3: A Comparative Study

Abstract: Lipase from Candida rugosa (CRL) was immobilized by physical adsorption onto Al2O3. The immobilization yield was more than 95% during 30 min. The properties of free and immobilized enzyme were also searched and compared. The optimum pH was shifted from 7 to 8.5 by immobilization of the enzyme. The maximum activity of the free and the immobilized enzymes occured at 35 and 40°C, respectively.