Squalene from Fish Livers Extracted by Ultrasound‐Assisted Direct In Situ Saponification: Purification and Molecular Characteristics.

An ultrasound‐assisted direct in situ saponification (U‐DS) process was developed to extract unsaponifiable matter (rich in squalene) from the livers of four fish species, sea bass, skipjack tuna, gray bamboo shark, and spot‐tail shark. The conventional solvent extraction method was used for comparison. Box–Behnken experimental design (BBD) was adopted to optimize the independent variables including the biomass/methanol ratio (1:3 to 1:9 w/v), 50% KOH volume (1–12 mL), and sonication time (0–30 min) over the unsaponifiable yield. With the conventional process, the yield of squalene was 0.10 ± 0.02 to 5.52 ± 0.06 g (100 g)−1, whereas the U‐DS process rendered the yield of 0.13 ± 0.03 to 6.86 ± 0.05 g (100 g)−1, depending on the fish species. After extraction, squalene was further concentrated (purity ≥60%) from all fish species via fractional crystallization (yield of squalene concentrate ranged from 48.35% to 74.49%) and purified using a silica gel column with a maximum recovery up to 98%. For all the fractions, components were examined using thin layer chromatography (TLC). Squalene was qualitatively and quantitatively analyzed using reversed‐phase high‐performance liquid chromatography (RP‐HPLC). Entire extraction processes yielded squalene with a purity of ≥94%. Fourier transform infrared (FTIR) analysis confirmed the native structure of squalene with six nonconjugated bonds, suggesting no degradation of squalene taken place during the U‐DS process. Thus, the U‐DS process along with fractionation and purification could be used for recovering the squalene from fish livers. [ABSTRACT FROM AUTHOR]