Article

Inhibition of Δ5-desaturase in polyunsaturated fatty acid biosynthesis by (−)-asarinin and (−)-epiasarinin

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  • Suntory Global Innovation Center
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Abstract

An extract of Chinese medicine, saishin (Asiasari radix), was found to increase the mycelial dihomo-γ-linolenic acid content of an arachidonic acid-producing fungus, Mortierelia alpina, with an accompanying decrease in its arachidonic acid content. The factors responsible for this phenomenon were isolated and identified as (−)-asarinin and (−)-epiasarinin, which are the enantiomers of (+)-episesamin and (+)-sesamin, respectively. The inhibitory effects on the Δ5-desaturase in rat liver microsomes of these factors were in the order of (+)-sesamin > (−)-epiasarinin > (−)-asarinin > (+)-episesamin. Kinetic analysis showed that (−)-asarinin and (−)-epiasarinin are non-competitive inhibitors, the Kis for rat liver Δ5-desaturase being 2.8 × 10−4 and 7.1 × 10−4 M, respectively, which are almost the same as the values of the (+)-enantiomers.

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... Asarinin and sesamin, the major ingredients pertaining to the lignan phytochemical group in AR, have a variety of pharmacological activities consistent with the efficacy of AR, including antipyretic, antiinflammatory, and immunosuppressive effects [2,[17][18][19][20][21][22][23]. e latest network pharmacology research also shows that asarinin and sesamin may be the key active ingredients for AR to exert antiinflammatory and analgesic effects. ...
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Asari Radix et Rhizoma (AR) is a widely-used Chinese herbal medicine containing multiple active lignans and rare nephrotoxic components-aristolochic acids derivatives (AAs). However, the current quality control method carried out by Chinese Pharmacopoeia has defects in trace AAs detection and insufficient marker ingredients, which is unable to comprehensively evaluate the efficacy and safety of AR. To improve the quality control method of AR, a rapid, sensitive, and reliable chromatographic analytic method based on ultra-high-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS) was established for the simultaneous analysis of multiple AAs and lignans in AR samples. Positive electrospray ionization mode with multiple reaction monitoring (MRM) was applied for the detection of the eight analytes. The method showed available linearity (R2 ≥ 0.991), the limit of quantification (2–5 ng/mL), precision (RSD <8.12%), and accuracy (89.78–112.16%). A total of 6 AAs and 2 lignans were quantified for their content in 15 AR samples. The content of AA-IVa, AA-VIIa, and aristololactam I (AL-I) was much higher than the AA-I controlled by pharmacopoeia. Considering the potential toxicity of AAs, AA-IVa, AA-VIIa, and AL-I should also be controlled in AR. A considerable amount of active sesamin was detected in AR, suggesting that it could be added as a quality marker for the quality control of AR. The newly developed analytical method could be applied for the fast evaluation of toxic AA’s content and quality during quality control of AR or preparations containing AR.
... Trans-kielcorin and trans-isokielcorin B were effective in preventing perturbation of cell GSH homeostasis, as revealed by measuring reduced and oxidised GSH, lipid peroxidation and cell viability after inducing toxicity with or without the studied compounds at different concentrations [272]. The lignan (+)-sesamin and related lignans present in sesame seeds or its oil are specific inhibitors of Δ 5 -desaturase in polyunsaturated fatty acid biosynthesis in both microorganisms and animals [273,274] (+)-episesamin, (-)-asarinin and (-)-epiasarinin also inhibited only Δ 5 -desaturase of the fungus and liver. In an analogous study Umeda Sawada et al [275] demonstrated that sesamin inhibits the Δ 5 -desaturation of n-6 fatty acid (dihomo-γ-linolenic acid to AA), but not that of n-3 fatty acid to eicosapentaenoic acid in rat livers. ...
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The inhibitory effects of the positional isomers of trans-18:1 acids on the desaturation of palmitic acid to palmitoleic (delta 9-desaturase), linoleic to gamma-linolenic (delta 6-desaturase) and eicosa-8,11,14-trienoic to arachidonic acid (delta 5-desaturase) were investigated. These trans-18:1 acids were found to be inhibitory for the microsomal delta 6-, delta 9- and delta 5-desaturases of rat liver. The position of the double bond in the trans-18:1 acids seems to be important in determining the degree of inhibition. At inhibitor/substrate ratio of 3:1, the delta 6-desaturase was most strongly inhibited by trans-delta 3, -delta 4, -delta 7 and -delta 15-18:1 isomers, whereas the delta 9-desaturase was most strongly inhibited by trans-delta3, -delta 5, -delta 7, -delta 10, -delta 12, -delta 13 and -delta 16 isomers. At inhibitor/substrate ratio of 6:1, the delta 5-desaturase was most strongly inhibited by delta 3-, delta 9-, delta 13- and delta 15-isomers. When 18:0 was added to the incubations of 16:0, 18:2 and 20:3 at the same I/S ratios used for the trans-18:1 acids, weak inhibition for delta 9- desaturase and no inhibition for delta 5- and delta 6-desaturases was observed.