Semi-synthetic route of luteolin
Luteolin was obtained from hesperidin, which was extracted from orange peel with biological activity, through three-step reaction. The total yield of the product was about 40 ~ 47%.
The first step is dehydrogenation: hesperidin is dehydrogenated in iodine/pyridine, iodine/dimethyl sulfolone/sulfuric acid and other systems. The reaction temperature is 50 ~ 120℃ and the reaction time is 5 ~ 16 hours. The precipitates are dissolved in lye after washing, and then methanol is added and the PH is adjusted to acidity.
The second step is the hydrolytic reaction of glycosides: Dioxamine is released in hydrolytic systems such as methanol/hydrochloric acid, glycol/sulfuric acid, glycol/hydrochloric acid, ethanol/hydrochloric acid, methanol/sulfuric acid. The reaction temperature is 50-120 ℃ and the reaction time is 1-5 hours. After cooling, the reaction products are separated and geranyl is obtained by recrystallization with organic solvent.
The third step is demethylation reaction: Geraniol was demethylated under hydrobromic acid, hydrobromic acid/acetic anhydride, hydroiodic acid/acetic anhydride and other demethylation reagent systems. The reaction temperature was 70 ~ 120℃ and the reaction time was 5 ~ 12 hours. The yellow products precipitated by cooling were filtered and washed to neutral, and then dried at low temperature to obtain luteolin crude products.

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