Effects of antioxidative substances from seaweed on quality of refined liver oil of leafscale gulper shark, Centrophorus squamosus during an accelerated stability study

The Potential of Phaeodactylum as a Natural Source of Antioxidants for Fish Oil Stabilization

Worldwide, fish oil is an important and rich source of the health-beneficial omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). It is, however, troubled by its high susceptibility towards lipid oxidation. This can be prevented by the addition of (preferably natural) antioxidants. The current research investigates the potential of Phaeodactylum carotenoids in this regard. The oxidative stability of fish oil and fish oil with Phaeodactylum addition is evaluated by analyzing both primary (PV) and secondary (volatiles) oxidation products in an accelerated storage experiment (37 °C). A first experimental set-up shows that the addition of 2.5% (w/w) Phaeodactylum biomass is not capable of inhibiting oxidation. Although carotenoids from the Phaeodactylum biomass are measured in the fish oil phase, their presence does not suffice. In a second, more elucidating experimental set-up, fish oil is mixed in different proportions with a Phaeodactylum total lipid extract, and oxidative stability is again evaluated. It was shown that the amount of carotenoids relative to the n-3 LC-PUFA content determined oxidative stability. Systems with a fucoxanthin/n-3 LC-PUFA ratio ≥ 0.101 shows extreme oxidative stability, while systems with a fucoxanthin/n-3 LC-PUFA ratio ≤ 0.0078 are extremely oxidatively unstable. This explains why the Phaeodactylum biomass addition did not induce oxidative stability.

Effect of antioxidant compounds from seaweeds on storage stability of C20-22 polyunsaturated fatty acid concentrate prepared from dogfish liver oil

Ethyl acetate extracts of seaweeds were chromatographically fractionated to yield 14-methyl pentyl tetrahydro-8-hydroxy-10-methylnaphthalene-8-carboxylate (1) and tetrahydro-4-isopropyl-9-(9, 14-dimethyldec-9-enyl)-pyran-1-one (2) from Sargassum ilicifolium, whereas Padina gymnospora afforded dihydro-2-(10-(hydroxymethyl)-7,15-dimethyl-9-oxoundec-11-enyl)-2-methyl-2H-pyran-1(4H)-one (3) and 1-(decahydro-1-hydroxy-7-methyl-8-vinylnaphthalen-2-yl)ethanone (4) as major constituents. Compound 1 displayed significantly higher antioxidant activity (IC50 < 1 mg/mL, p < 0.05) comparable to other analogues (IC50 > 1 mg/mL). The C20-22 polyunsaturated fatty acid (C20-22 PUFA) concentrate (CFA) prepared from the deep-sea dogfish liver oil was added with the studied compounds and physiochemical properties and fatty acid composition during an accelerated storage were evaluated. No significant reduction in C20-22 PUFAs (∼6%) in the CFA treated with 1 as compared to that with the control (∼35%) was recorded. A greater induction time was observed for the CFA supplemented with 1 (6.8 h) than other compounds (≤6 h) and control (∼1.6 h), maintaining the oxidation indices of the CFA within desirable limits.