Acemannan, Poly Acetyl Mannose or Poly Acetylated Mannans, is the truncated name of the primary active ingredient in Aloe vera gel. While doing investigational new drug research in the mid 80’s, Carrington Laboratories requested the name “Acemannan” from the American Medical Association´s United States Adopted Names Council, (USAN). The request was granted resulting in a new adopted name for a drug: “Acemannan is a purified drug comprised of a highly dispersed ß1,4-linked acetylated polymannan with an average molecular weight of 1 to 2 million Daltons.” Acemannan; therefore, is a naturally occurring active ingredient of Aloe vera that can be isolated and purified into a drug. Acemannan consists of a polymer of β-1,4 linked mono-acetyl mannose as the main sugar present and with a broad range of molecular weights from the low thousands to the low millions found in the inner leaf parenchyma of Aloe vera leaves.

The only official definition of Acemannan is the USAN definition. Indexing services like the Chemical Abstracts Service Registry (CAS Registry®) compiles information such as this and lists it in their database. They do not define the compound or substance but rather assign a unique numerical identifier –the CAS number- that helps prevent confusion when selecting a chemical or substance.

In polymer chemistry highly dispersed means there is a large distribution, or spread, in the molecular weights (“MW”) of the polymer. Accordingly if the average MW is one to two million Daltons, this means that the range goes from the low end of the molecular weight in the thousands to the millions of Daltons on the high end. All ß1,4-linked acetylated polymannans under the distribution curve are Acemannan.

The scientific community has often questioned which range of molecular size of Acemannan is the most biologically active. Im et. al. published research in a study entitled “Identification of optimal molecular size of modified Aloe polysaccharides with maximum immune-modulatory activity”. In that study Professor Im noted that “the optimal molecular size exhibiting maximum immune-modulatory activity is between 5 and 400 KDa” and that “polysaccharides larger than 400 KDa have only marginal immune-modulatory activity, while polysaccharides smaller than 400 KDa have potent immune-modulatory activity”. “Da” is the abbreviation of Dalton, the international unit of molecular weight. “K” is the abbreviation of 1,000. “KDa” is the abbreviation of thousands of Dalton. Not all of the Acemannan is equally biologically active when taken orally: medium size polymers with molecular weights lower than 400KDa show the highest immune-modulatory activity while the largest molecular weights show less activity.