Oxidative Properties of Lignan
Lignin Compounds
Lignin Monomers
Abstract
The lignin polymer is synthesized via oxidative coupling of three basic monomers: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. These three monomers each possess a phenol group that stabilizes the radical intermediate generated during the oxidation reaction. Two radicals dimerize together to create lignan, which is biologically active and currently being tested for pharmacological properties such as, antiallergy effect, analgesic effect, and stress reducing activity. HPLC was used to study the oxidation of coniferyl alcohol, the monomeric lignan, and validate the formation of dimers. The mechanisms of this dimer formation were also studied to better understand the oxidative coupling of the lignin monomers.
Oxidation of Monomers
Beaker reactions with varying reaction conditions were completed to analyze the oxidation of each monomer. For each monomer, 100 mL of a 2 mM standard solution of the monomer was made using 50/50 dioxane/pH 5 buffer. Three reactions were then completed with varying concentrations of hydrogen peroxide in the presence of HRP. The first reaction was composed of 5 mL of the substrate, 10 µL of hydrogen peroxide (1 mM final concentration hydrogen peroxide) and 5 µL of HRP. The second reaction was composed of 5 mL of the substrate, 5 µL of hydrogen peroxide (0.5 mM final concentration hydrogen peroxide) and 5 µL of HRP. The third reaction was composed of 5 mL of the substrate, 5 µL of hydrogen peroxide (0.25 mM final concentration hydrogen peroxide) and 5 µL of HRP. These reactions were then analyzed on the HPLC for oxidation products of each monomer.
Lignan
Background
Lignan is formed from the oxidative coupling of two lignin monomers. The dimers are often linked between the beta-carbons on the side chain of each monomer. Many of the dimers stated often in literature possess this linking structure. These dimers have biological activity, whereas the larger structure of lignin does not. This allows them to have potential healths benefits associated with them. Some of these benefits are anti-microbial, anti-inflammatory, and antioxidant. The relationship between allergies and lignan has also been studied. It might be related to having an anti-histamine effect on allergy symptoms.