Hesperidin occurs as a colourless or pale yellow coloured, tasteless, crystalline glycoside with a melting point of 258–260°C. Chemically it is (S)-7-[[6-O-(6-deoxy-alpha-L-mannopyranosyl)-beta-D-glucopyranosyl] oxy]-2,3-dihydro-5-hydroxy-2-(3-hydroxy-4-methoxyphenyl)-4H-1-Benzopyran-4-one and has a molecular formula C₂₈H₃₄O₁₅. It is freely soluble in alcohol and formamide, moderately soluble in ether, slightly soluble in water (1g/50L), methanol, hot glacial acetic acid, almost insoluble in acetone, chloroform and benzene and also soluble in dilute alkalies. On hydrolysis it yields hesperitin together with dextrose and rhamnose.

Isolation

Several classic methods are reported by many workers for the isolation of hesperidin from orange peel and other citrus sources. Due to its insolubility and crystalline nature it may be isolated with relative ease. The yield may vary from 3 to 5 mg/g of the dried peel depending on the species and other factors.

Method

1. 100 g of dried powdered orange peel is taken in a round bottomed flask with 300 ml of petroleum ether (40°–60°C) and boiled under reflux for 1 h.
2. Filter hot through a Buchner funnel and air dry the residue for complete removal of the solvent.
3. Transfer it into another round bottomed flask, add 500 ml methanol and boil under reflux for 2 h.
4. Filter hot and concentrate the filtrate to a syrupy liquid in a rotary vacuum evaporator.
5. To the syrupy liquid add 50 ml of 6% acetic acid and mix gently. The precipitated hesperidin is separated by filtration through a Buchner funnel. It is washed with 6% acetic acid and dried at 60°C.
6. For purification make a 5% solution of the crude hesperidin in dimethyl sulphoxide and warm to 60–80°C on a water bath with stirring. Add equal volume of water and pure hesperidin precipitates as the mixture cools.
7. Collect the precipitated hesperidin by filtration under reduced pressure, wash with warm water and isopropanol. Dry the product in a desiccator to constant weight.