The metabolism of the plant lignans matairesinol, secoisolariciresinol, pinoresinol, syringaresinol, arctigenin, 7-hydroxymatairesinol, isolariciresinol, and lariciresinol by human fecal microflora was investigated to study their properties as mammalian lignan precursors. The quantitative analyses of lignan precursors and the mammalian lignans enterolactone and enterodiol were performed by HPLC with coulometric electrode array detector. The metabolic products, including mammalian lignans, were characterized as trimethylsilyl derivatives by gas chromatography-mass spectrometry. Matairesinol, secoisolariciresinol, lariciresinol, and pinoresinol were converted to mammalian lignans only. Several metabolites were isolated and tentatively identified as for syringaresinol and arctigenin in addition to the mammalian lignans. Metabolites of 7-hydroxymatairesinol were characterized as enterolactone and 7-hydroxyenterolactone by comparison with authentic reference compounds. A metabolic scheme describing the conversion of the most abundant new mammalian lignan precursors, pinoresinol and lariciresinol, is presented.

Twenty-four plant lignans were analyzed by high-performance liquid chromatography-tandem mass spectrometry in bran extracts of 16 cereal species, in four nut species, and in two oilseed species (sesame seeds and linseeds). Eighteen of these were lignans previously unidentified in these species, and of these, 16 were identified in the analyzed samples. Four different extraction methods were applied as follows: alkaline extraction, mild acid extraction, a combination of alkaline and mild acid extraction, or accelerated solvent extraction. The extraction method was of great importance for the lignan yield. 7-Hydroxymatairesinol, which has not previously been detected in cereals because of destructive extraction methods, was the dominant lignan in wheat, triticale, oat, barley, millet, corn bran, and amaranth whole grain. Syringaresinol was the other dominant cereal lignan. Wheat and rye bran had the highest lignan content of all cereals; however, linseeds and sesame seeds were by far the most lignan-rich of the studied species.

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The effects of caffeoylglycosides (forsythiaside, suspensaside, acteoside, and 3-hydroxyacteoside), isolated from dried fruits of Forsythia species, on the formations of the 5-lipoxygenase products 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) and leukotriene B4 (LTB4), the 15-lipoxygenase product 15-hydroxy-5,8,11,13-eicosastetraenoic acid (15-HETE) and the cyclooxygenase products 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT), thromboxane B2 and 6-keto-PGF1a in rat peritoneal cells and human peripheral polymorphonuclear leukocytes were studied. Forsythiaside, suspensaside, acteoside, and 3-hydroxyacteoside were found to inhibit selectively the formation of the 5-lipoxygenase products 5-HETE and LTB4 in human peripheral polymorphonuclear leukocytes; their concentrations for 50% inhibition (IC50) of 5-HETE formation being 1.92,49.0, 4.85, and 40.0 tM, and their IC50 values for LTB4 formation being 1.01, 8.85, 2.93, and 8.50 iM, respectively.Forsythiaside, suspensaside, acteoside, and 3-hydroxyacteoside inhibited the formation of 5-HETE from arachidonic acid in rat peritoneal cells, their IC50 values on its formation being 2. 50, 7.97, 5.27, and 19.3 iM, respectively. Forsythiaside caused non-competitive inhibition of 5-HETE formation.