Lihong Xing

Separation, Purification, and Identification of (3S,3′S)-trans-Astaxanthin from Haematococcus pluvialis

A simple, low-cost method of separation and purification for preparing (3S,3′S)-trans-astaxanthin from Haematococcus pluvialis was established in this study. Crude extracts were separated from dry algal cells by extraction. The extracts were then saponified at 4°C for 15 h and at 22°C for 3 h with 0.02 M NaOH in the reaction mixture with lower isomerization of trans-astaxanthin to cis isomers. The saponified pigment extracts were mixed with distilled water and n-hexane at 1:1:1 volume ratio. Low-pressure column chromatography of silica gel (300-400 mesh) with different eluents was used to prepare high-purity (> 80%) all-trans-astaxanthin. Supersaturated solution of astaxanthin in acetone was then crystallized for 72 h at 4°C, and the purity of all-trans-astaxanthin crystalline powder was confirmed to be > 96.5% by HPLC. And the 3S,3′S isomers were identified and characterized by HPLC-APCI-MS, 1H NMR, 13C NMR, and HPLC-UV.

Assessment and comparison of in vitro immunoregulatory activity of three astaxanthin stereoisomers

In recent years, the immune-modulatory role of all-trans astaxanthin from different pigment sources has been studied. It was reported that all-trans astaxanthin might exist as three stereoisomers, and the composition of all-trans stereoisomers in natural materials differs from that of synthetic products. However, the different biological effects of various all-trans stereoisomers still remain unclear. In the present study, we evaluated the bioactivity of three astaxanthin stereoisomers, (3S,3’S)-trans-, (3R,3’R)-trans-and meso-trans-astaxanthin, in regulating cell-mediated immune response using mice lymphocytes and peritoneal exudates cells (PECs) systems. After the treatment with three astaxanthin stereoisomers (20 μmol L−1), the lymphocyte proliferation capacity, neutral red phagocytosis of PECs and natural killer (NK) cell cytotoxic activity were comparatively assessed. The results showed that all three astaxanthin stereoisomers significantly promoted lymphocyte proliferation, phagocytic capacity of PECs, and cytotoxic activity of NK cells. Moreover, the (3S,3’S)-trans-astaxanthin exhibited a much higher response than others.

Determination of nitrophenolate sodium in aquatic products by HPLC–MS/MS with atmospheric pressure chemical ionization

The paper describes an efficient method for the determination of nitrophenolate sodium in aquatic products by HPLC combined with atmospheric pressure chemical ionization with tandem mass spectrometry (LC–APCI-MS/MS). Analytes were extracted from aquatic products by acetonitrile, the extracts were degreased by alumina and concentrated, the concentrated solution was further purified by Oasis HLB cartridge. Finally, the analytes were separated and detected by LC–APCI-MS/MS in negative ion mode. Excellent linearity with correlation coefficients of more than 0.995 was observed in the concentration range of 2–200 μg/L for p-nitrophenol sodium and 2-methoxy-5-nitrophenolate sodium, and 5–200 μg/L for ο-nitrophenol sodium. Recovery rates of nitrophenolate sodium between 86.1–94.3% were achieved. Limit of quantitation of p-nitrophenol sodium and 2-methoxy-5-nitrophenolate sodium was 2 μg/kg and ο-nitrophenol sodium was 5 μg/kg, with relative standard deviations <10%. This method was employed in the practical analysis of spiked and naturally contaminated aquatic products.