Lignans

Lignans are a class of natural organic compounds formed by polymerizing two or three molecules of phenylpropyl groups in different forms, mostly distributed in angiosperms and gymnosperms. It can be divided into two major categories: A compound polymerized by two molecules of a phenylpropyl derivative through its side chain β-position is called lignan. A compound in which a side chain of one molecule of phenylpropyl group is bonded to a benzene ring of another molecule or a two part is linked by an oxygen atom is called neolignan. In addition, there are compounds which are polymerized from three molecules of phenylpropyl group, called sesquilignan; compounds which are condensed with flavonoids or chalcone and phenylpropene derivatives, called flavonolignan or Ketone lignan (xanthonolignan) and the like. After the lignans are condensed by two molecules of phenylpropyl β-carbon, the oxygen-containing groups on the side chain γ-carbons can be dehydrated and condensed with each other to form substituted tetrahydrofurans, hemiacetals, lactones, tetrahydronaphthalenes or cyclooctenes. structure. Therefore, lignans can be divided into more types. Such as monoe-poxy lignan, lignanolide, cycloli-gnan and the like. More than 200 lignans and more than 100 new lignans have been obtained from the plant kingdom. Chinese medicine Schisandra, Acanthopanax senticosus, Gewang, Luoshi, Niuzizi, Yuanzhi, Forsythia, safflower, Asarum, etc., all contain lignans. In plants, lignans exist in free or sputum form, most of them are optically active, mostly free of colorless crystals, and some new lignans are oily. Soluble in organic solvents, insoluble or insoluble in water. Terpenes are more soluble in alcohols or water and can be hydrolyzed by acids. The extraction of lignans is usually carried out by using methanol or ethanol to extract total lignans, and then separating the single components by chromatography or fractional crystallization. Most lignan components can develop color in the presence of concentrated sulfuric acid. If the molecule contains a phenolic hydroxyl group, it can react with some phenolic reagents such as ferric chloride reagent, alkaline diazotized p-aminobenzenesulfonic acid reagent, etc. to exhibit different colors. Some lignans can react with carbon tetrachloride solution of antimony pentachloride to develop color. For example, podophyllin is brownish yellow, and alpha-tobacco is present in purple. Many lignan components may exist as stereoisomers due to saturated cyclic moieties. It has been observed that the lignan component present in some traditional Chinese medicines is unstable in nature, is easily isomerized by the influence of acid or alkali, and is converted into its stereoisomer. For example, podophyllin has a remarkable anticancer effect, and it is easily converted into Picrop-odophyllin in an alkaline solution: if it is affected by phosphorus trichloride, the C1-OH translocation generates a ghost. Epi-podophyllotoxin, picropodophyllin and its derivatives have no anticancer activity. Various lignans have been found to have anti-cancer, anti-fungal, insecticidal, leukocyte-reducing, alanine-lowering enzyme, liver-protecting, anti-cough, and diarrhea activities, but not much as medicinal. Derivatives of podophyllin are used as anticancer drugs. The lignans in Schisandra have a function of apocytosine transaminase to treat hepatitis.