Aloe vera, Quality Inspection and Indentfication

Editors Note:The IASC is currently considering using NMR spectroscopy in its certification program.

This article appeared in the January/February 1998 issue of Agro Food Industry Hi-Tech. It was reprinted with permission from ROVI GmbH. There are supporting charts accompanying this article that were not published here. To receive a complete copy of the article, please call the IASC at (972) 258-8772.

By Bernd Diehl
Spectral Service

Ernst E. Teichmuller

Aloe vera. Known to man since time immemorial, this plant is efficacious in many different ways. Its effectiveness as a moisturiser, in increasing the speed of wound healing, its anti-inflammatory effect and many other effects, right through to the stimulation of the immune system, have been examined and described in numerous publications (over 1,000 in total).

For the most part, examinations of this type have been carried out using Aloe vera raw material manufactured in accordance with the quality requirements of the International Aloe Science Council. These scientific papers have confirmed claims that folk medicine has been making for generations.

This makes it clear that it is only of the fresh plant that the desired and anticipated effect of Aloe vera may be expected, or failing that, of superior quality Aloe vera raw material containing the same combination and variety of substances as are found in the fresh plant.

Modern marketing has incorporated these claims into advertising, thus bringing Aloe vera closer to the consumer. Having seen the advantages, the consumer has then, with his or her behaviour, helped to make Aloe vera a success. Successful products lead to competition between suppliers; thus terms of delivery, price and quality become decisive purchasing factors.

This is where the problems began for the purchasing companies. In the absence of any objective method of demonstrating the quality of Aloe vera, assessing its quality was more or less a matter of trust between the seller and purchaser. Increasing pressure from the competition, led some suppliers to manipulate their products, at the expense of quality, in order to avoid price-related pressure.

Not until late 1992 did Ron Pelley et al. in their paper entitled "Current Status of Quality Control of Aloe barbadensis Extracts" present a way of comparing products with a standard. This ARF (Aloe Research Foundation) standard, which comprises an extensive collection of data on Aloe vera, was produced in accordance with IASC guidelines, taking into consideration the various cultivation regions and seasonal conditions that exist.

It was at the time these trials were taking place, then, that it became possible for the very first time to confirm suspicions that the quality of Aloe vera was being deliberately manipulated. Even though the Ron Pelley method was extremely time-consuming, and supplied only a comparison with a standard, it was still included in the IASC certification programme. For the first time ever, it was now possible to examine commercially available Aloe vera raw materials for their purity and quality.

The results were shattering. There were cases of Aloe vera powder being found that contained up to 90% maltodextrin. The results of a substantial initial assessment were published by Nicholas F. Schmidt et al. at an IASC congress in August 1995, under the heading "The comparative purity of commercially available Aloe Vera."

The quality of Aloe vera became a subject for discussion not just in the USA, but in Europe, too. As the result of one such discussion, the Cologne-based company Spectral Service commenced work on quality verification.

The New Method
Aloe vera is a natural substance, consisting of a great variety of individual components. The three main components are glucose (a monomeric sugar constituent), malic acid (a preliminary stage for sugar in the plant's organism), and the polysaccharide acemannan*, the core of Aloe vera.

Acemannan is composed of a long chain of separate sugar constituents. These constituents are not the glucose mentioned above, but rather mannose, a similar molecule. On average, each mannose has one acetate group on one of the three remaining positions in the ring. The polysaccharide can be isolated from the plant for analytical purposes. In the 1H-NMR spectrum, these different acetate groups give a signal which can be utilised as the "fingerprint" of the Aloe vera. Manipulation of this signal is practically impossible.

Aloe vera juice is a "fruit juice", in just the same way as apple juice or other juices are. The best quality criterion is comparison with fresh juice. Unless it is pasteurised or preservatives are added, Aloe vera juice - like other freshly squeezed juices - begins to ferment within a short period of time. The preservatives benzoic acid and sorbic acid can clearly be recognised in the NMR spectrum.

After the Aloe vera has been harvested, the lactobacillus very quickly causes lactic acid fermentation to occur, which is similar to what happens when yoghurt is produced. During this process, lactic acid - not a natural component of Aloe vera - is produced.

A high lactic acid content is a negative characteristic of the quality of Aloe vera, unless it is one's aim to sell the product "Aloe vera yoghurt". Further substances that are produced by enzymes typical of Aloe vera in the so-called citric acid cycle are fumaric acid, succinic acid and pyruvate.

The citric acid cycle is interrupted after the harvest takes place, since no further photosynthesis is possible; nevertheless, a number of enzymes continue to work on, thus enriching these compounds.

In addition to the enzymatic decomposition and fermentation, there is also a chemical decomposition, during which the acemannan releases acetate groups, thus producing acetic acid. This and the production of formic acid are also negative quality characteristics.

Preservatives must be added to liquid Aloe vera products to guarantee their stability. These essential substances are easily recognisable in the 1H-NMR spectrum.

These additives are to be declared in the list of raw materials. Should the declaration be omitted, or other cheap polysaccharides such as maltodextrin be added to the Aloe vera, this constitutes fraud. Evidence of the presence of these substances can, of course, also be provided by NMR spectroscopy.

By means of NMR spectrum, it is possible to record all the essential components of Aloe vera and thus make a clear statement regarding the quality of the product. Impurities, be they natural or artificial, can be detected. Decomposition products give information about the period of time elapsing between the leaves being harvested and processed, or about the age of the raw material.

The requirements for compulsory declaration and product safety both call for the listing of full details of all substances contained in the product. If, with raw materials of plant origin, a multitude of separate substances typical of that species are to be expected, then any extra auxiliary materials or additives that have been added must be declared, particularly if these substances are products that are not typical of the species. The efficacy of Aloe vera depends on the activity and purity of the raw material. Only pure, unadulterated Aloe vera can have the effect of Aloe vera.

* The word acemannan is a term generally used for a specific range of molecular weight polysaccharide. Acemannan is a term trademarked by Carrington Laboratories.