GLA occurs naturally in the human body, where it is synthesised from linoleic acid by the D6-desaturase enzyme. It is the precursor for a range of physiologically active compounds including the prostaglandins and leukotrienes. A number of disease states are associated with low levels of GLA in the body and there is therefore a theoretical basis for supplementation of the diet with GLA to correct the deficit. Pharmaceutical product licences have been obtained for treatment of eczema and mastalgia.
GLA is not a common fatty acid in food, but is found in the seed oils of a
number of plant species. The oil of choice for pharmaceutical use has been from
the evening primrose (Oenothera
spp.). Over 25 years, this wild plant has been bred to produce varieties
suitable for agricultural production, and the cultural practices have been
refined. Recently, the enzymes responsible for the production of GLA in
cyanobacteria and in borage (Borago officinalis) have been cloned and successfully introduced into plants which do not
normally produce GLA, thus paving the way for much cheaper supplies.
Unfortunately, recent clinical trials into the effect of GLA on diabetic
neuropathy and the side effects of radiotherapy have not been sufficiently
persuasive to allow the granting of product licences, and the company
responsible has now largely withdrawn from this area, preferring to concentrate
on synthetic raw materials. This illustrates the difficulties in
commercialising plant-derived compounds as pharmaceuticals, and means that the
most likely routes of commercialisation for GLA for the foreseeable future will
be through health-food and nutritional products.