Investigation of polysaccharide composition in medicinal and non-medicinal aloes

The genus Aloe comprises over 500 species of leaf succulents found throughout Africa, Madagascar and the Arabian Peninsula. Aloe vera is a particularly widely known species, and is used as an ingredient in products from herbal medicine to cosmetics and household commodities. Aloe vera dominates the market worldwide, but as many as 25% of the Aloe species are used locally, a few of them even supported by small industries [1,2]. The major chemical components of the tissue used in these products are polysaccharides – highly complex molecules found in the spongy leaf mesophyll (referred to as Aloe gel). Studies of other plants used in traditional medicine have identified bioactive polysaccharides and shown them to have immune-modulatory activity [3]. In Aloe, polysaccharides extracted from the leaf mesophyll have been associated with both anti-inflammatory and immune-modulatory activity [4]. As polysaccharides are highly complex, they are often studied indirectly using monosaccharide analyses. A recent study showed that the monosaccharide composition of 31 species of Aloe is conservative, with 90% of the variation accounted for glucose, mannose and xylose as the major constituents [5]. The extent to which leaf mesophyll polysaccharides differ between Aloe species has, until now, remained unclear. Here, we present data from an initial study of the polysaccharide composition of 11 species of Aloe, using carbohydrate microarrays and 23 monoclonal antibodies binding to epitopes representing six distinct types of plant polysaccharides [6,7]. Marked variation in the binding patterns were observed between the studied species, indicating potential diversity of polysaccharides within the genus Aloe not observed in analyses of the monosaccharides.

Acknowledgements: This work was supported by the Villum Foundation as part of the PLANET project: Understanding plant evolution and diversity in a changing world. Martin Aarseth-Hansen and Paul Rees are acknowledged for assistance with the collection of plant material, and Paul Knox for the monoclonal antibodies.

Keywords: Aloe, microarrays, polysaccharides, medicinal plant use, gel.

References:

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