Aloin

• Barbaloin
• 10 - ( 1 ', 5'- Anhydroglucosyl ) aloe-emodin -9-anthrone
• Anthrone, 1,8- dihydroxy-3 -hydroxymethyl- 10RS - ( β )-D- ( glucopyranosyl )

Attention

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Aloin (also barbaloin ) is a substance from the group of 1,8- Dihydrohxyanthracene, which is isolated from species of aloe. The glycosidic substance crystallizes in yellow needles, smells slightly of aloe and has a bitter taste. Aloin comes in two diastereomeric forms, the aloin A ( barbaloin A) and aloin B ( barbaloin B) that occur depending on the species in varying proportions.

History

1851 aloin was first isolated as a natural product from Barbados Aloe. This was recognized by E. Leger 1897 as anthraquinone derivative. In 1952 it succeeded mill man to elucidate the exact structure.

The previously known as Isobarbaloin and identified by the Rosenthaler reaction ingredient could be assigned by Vötig 1982, the structure of 7- Hydroxyaloin that. Both diastereomeric forms in the West Indian aloe, however, does not occur in the Cape Aloe

Occurrence

Aloin does not only occur in more than 20 species of Aloe, but also in the American buckthorn bark ( Rhamnus purshiana ). The content of aloin in Aloe different varieties varies depending on their nature, origin and seasonal conditions between 5 to 40 % (based on aloe drug, so the dried sap ).

In vivo studies on the biosynthesis of Aloine have shown that aloin B is synthesized by the plant, while the isomer aloin A is formed secondarily by conversion of aloin B.

Production and representation

In addition to the extraction of dried aloe and subsequent workup by means of recrystallization or column chromatography, it is possible in a wet-chemical route from aloe-emodin -9-anthrone, α - Bromacetoglucose sodium hydroxide and the diastereomer mixture of aloin A and B to synthesize aloin.

Importance

Aloin is the active ingredient of the herbal drug aloe, which can be used in a standardized preparation as a laxative for short-term treatment of occasional constipation. Prolonged intake of aloe can cause disturbances in water and electrolyte balance, especially potassium losses. In urine protein and blood may occur (proteinuria, hematuria). In overdose it comes to toxic symptoms which manifest themselves in spasmodic pain and severe diarrhea, which can lead to life-threatening electrolyte and water losses. Also, kidney infections are described. The therapeutic importance of Aloe has declined against the background that there are better tolerated substances.

Proof

A recorded in chloroform sample shows - applied to a sample medium ( TLC plate ) - after spraying with a methanolic 10% KOH solution a yellow color which under UV light (365 nm) increased. This proof is based on the fact that shifts in the alkaline range the anthrone anthranol - equilibrium to the side of the Anthranolform. By means of UV -VIS spectroscopy can be three peaks at 297, observed 287 and 354 nm.