ABSTRACT
Sesamin, sesamolin (lignans) and sesamol--from sesame seed (Sesamum indicum L.)--are known for their health promoting properties. We examined the inhibition effect of sesamol, a phenolic degradation product of sesamolin, on the key enzyme in melanin synthesis, viz. tyrosinase, in vitro. Sesamol inhibits both diphenolase and monophenolase activities with midpoint concentrations of 1.9 µM and 3.2 µM, respectively. It is a competitive inhibitor of diphenolase activity with a K(i) of 0.57 µM and a non-competitive inhibitor of monophenolase activity with a K(i) of 1.4 µM. Sesamol inhibits melanin synthesis in mouse melanoma B16F10 cells in a concentration dependant manner with 63% decrease in cells exposed to 100 µg/mL sesamol. Apoptosis is induced by sesamol, limiting proliferation. This study of the chemistry and biology of lignans, in relation to the mode of action of bioactive components, may open the door for drug applications targeting enzymes.
Subject(s)
Benzodioxoles/metabolism , Benzodioxoles/pharmacology , Enzyme Inhibitors/metabolism , Enzyme Inhibitors/pharmacology , Melanins/biosynthesis , Monophenol Monooxygenase/antagonists & inhibitors , Monophenol Monooxygenase/metabolism , Phenols/metabolism , Phenols/pharmacology , Agaricales/enzymology , Animals , Apoptosis/drug effects , Catalytic Domain/drug effects , Cell Line, Tumor , Cooking , Copper/metabolism , Lignans/pharmacology , Mice , Monophenol Monooxygenase/chemistry , Oxidoreductases/antagonists & inhibitors , Protein Binding , Sesame Oil/chemistry , Spectrum AnalysisABSTRACT
Infrared (IR) heating offers several advantages over conventional heating in terms of heat transfer efficiency, compactness of equipment, and quality of the products. Roasting of sesame seeds degrades the lignan sesamolin to sesamol, which increases the oxidative stability of sesame oil synergistically with tocopherols. IR (near infrared, 1.1 to 1.3 microm, 6 kW power) roasting conditions were optimized for the conversion of sesamolin to sesamol. The resultant oil was evaluated for sesamol and tocopherol content as well as oxidative stability. The defatted flours were evaluated for their nutritional content and functionality. IR roasting of sesame seeds at 200 degrees C for 30 min increased the efficiency of conversion of sesamolin to sesamol (51% to 82%) compared to conventional heating. The gamma-tocopherol content decreased by 17% and 25% in oils treated at 200 and 220 degrees C for 30 min, respectively. There were no significant differences in the tocopherol content and oxidative stability of the oil. Methionine and cysteine content of the flours remained unchanged due to roasting. The functional properties of defatted flours obtained from either IR roasted or conventionally roasted sesame seeds remained the same. Practical Applications: Sesame oil is stable to oxidation compared to other vegetable oils. This stability can be attributed to the presence of tocopherols and the formation of sesamol, the thermal degradation product of sesamolin-a lignan present in sesame. Roasting of sesame seeds before oil extraction increases sesamol content which is a more potent antioxidant than the parent molecule. The conversion efficiency of sesamolin to sesamol is increased by 31% by infrared roasting of seeds compared to electric drum roasting. This can be used industrially to obtain roasted oil with greater oxidative stability.
