Preparation Of Novel Flavonolignans & Dihydroflavonols And Evaluation Of Their Antioxidant Activities

Flavonolignan, a part of hybrid lignan, is a kind of natural product consisting C6-C3-C6-C3-C6 unit, which is biosynthesized from a catecholic flavonoid coupling with a phenylpropanoid.Silybin is the. first natural flavonolignan, and also the most typical one which has the most correlative investigation. As the basis of hepatoprotective drug Flavobin? and Legalon?, silybin has excellent liver-protecting activity, but the bioavailability is limited due to its poor solubility. On the other hand, new activities are discovered continually as the pharmacological study continues. Hence, the structure-activity relationships of flavonolignans is worthy of investigation.Being a part of structural modification, our work started from changing the electron distribution of the whole molecular: the C-16 of B-ring was substituted by alkoxy groups, while the number and situation of substituted groups (hydroxyl and methoxyl groups) of E-ring were also changed. A series of silybin analogues were synthesized to evaluate the influence on antioxidant, hepatoprotective, anti-multidrug resistance and anti-tumor activities. Furthermore, a silybin analogue without C-4" hydroxyl substituted of E-ring was successfully synthesized with commercially available cinnamic alcohol. Consequently, apart from the oxidative coupling method, a new regiospecific route to construct benzodioxane structure of flavonolignans was discovered.A series of flavonolignans-scutellaprostin-A analogues was synthesized via coupling norwogonin with p-hydroxyl cinnamic alcohol derivatives. Correlative pharmacological study is under way.Dihydroflavonol moiety is included in the structure of silybin. Taxifolin, the material of silybin biosynthesis, is also a dihydroflavonol. Dihydroflavonols were found to possess a lot of biological activities such as antioxidant, antitumor and hepatoprotective. In order to find the relationships between bioactivities of silybin and its dihydroflavonol moiety, We synthesized a new series of 5,6,7-trioxygenateddihydroflavonols, modified their 6-position and B ring. The antioxidant activities of some compounds were tested.