Aloin

Aloin (aka aloin A, barbaloin) is a natural compound found in the exudate of dozens of species of Aloe, flowering succulent plants that grow or are cultivated worldwide. Aloin A has a diastereomer, aloin B¹ (aka isobarbaloin), that has similar properties.

Aloin, as barbaloin, was described in 1905 by Hooper Albert Dickinson Jowett and Charles Etty Potter at Wellcome Chemical Works (Dartford, UK). The authors stated that the compound was first isolated in 1850 and examined during the late 1800s by several researchers. Jowett and Potter reported an empirical formula for barbaloin of C₁₀H₁₈O₇, which turned out to be wildly incorrect.

In 1907, French chemist E. Léger reported that barbaloin transforms at 160–165 ºC to a product that he called “β-barbaloin”. It now appears that barbaloin epimerized to isobarbaloin, and what Leger made was a mixture of the two diastereomers². In the following years, Léger went on to publish more research on the aloins, particularly β-barbaloin.

The aloe species Aloe vera has a long history of use as an herbal medicine, beginning in ancient Greece and Rome. Uses included wound treatment and laxatives. In modern times, a variety of personal care products and over-the-counter (OTC) medications contain extracts of aloe plants. In 2002, however, the US Food and Drug Administration banned the use of aloe-containing products in OTC laxatives because aloin and its derivatives were suspected carcinogens.

Despite that setback, research on the medical value of aloins continues. Last July, Danilo Milardi at the National Research Council of Italy (Catania facility) and collaborators there and at the Universities of Catania and Naples wrote extensively about the therapeutic potential of aloins A and B. They reported these findings:

•  “The structural differences between these two epimers suggest that they may exhibit distinct pharmacological properties.”

• “. . . both epimers are not stable in aqueous solution . . . underscor[ing] the importance of addressing issues such as the need for encapsulation into effective drug-delivery systems to enhance stability.”

• “. . . an equimolar mixture of aloin A and aloin B demonstrated an ability to inhibit proteasome in-tube tests, which is suggestive of potential anticancer properties . . .”

• “Higher water stability and increased antiproliferative activity were observed by encapsulation in carbon dot nanoparticles, suggesting a promising potential for further in vivo studies.”

Aloinhazard information

Aloin fast facts

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