Physiological Activity of Docosahexaenoic Acid

Abstract

Docosahexaenoic Acid (DHA) has important physiological activities, such as reduction of the plasma cholesterol and triglyceride, lowering effect of systolic blood pressure, anti-inflamatory and anti-tumor activities, etc. Recent studies also strongly suggest that DHA plays a key role in the brain and retina. DHA commonly exists in fish oil obtained from sardines, mackerels, menhadens, etc. Usually, however, it contains DHA at a relatively low level (5-10%) and many other polyunsaturated fatty acids, and thus isolation of pure DHA from fish oil is quite difficult.
Recently, we found that (1) orbital fat of a bonito (Katsuwonus) and a tuna (Thunnus) fish was an excellent source of DHA, (2) DHA content in the total fatty acids of the orbital fat isolated from a bonito and a tuna fish was 42% and 30%, respectively, and (3) DHA existed as triglyceride in both cases.
Purification of DHA was examined after ethanolysis of orbital fat oil obtained from a tuna fish, and resulted in 95%-99% purity of DHA-ethyl ester by a new method using Ag ion.
Thus, finding of the excellent source and the purification procedure will greatly accelerate the research on DHA.