g-linolenic acid (GLA, 18:3 n-6) is a fatty acid which is of commercial interest as a component in both healthfood supplements and pharmaceutical products. It is normally made in the body by the 6-desaturation of dietary linoleic acid. The enzyme responsible is easily inhibited by 'lifestyle' factors, such as alcohol, saturated fats, viral infections and ageing. More seriously, a depletion of GLA is also associated with a number of disease states including cancer and diabetic neuropathy, and licensed pharmaceutical products are available for the treatment of eczema and mastalgia.

GLA is difficult and expensive to synthesise, and so natural sources have been used commercially. The first supplies were obtained from the seed oil of the evening primrose (Oenothera spp.) which normally contains 8-11% GLA. Later it was discovered that borage (Borago officinalis L.) seed oil contains more GLA (18-24%) but, although it has become established as a health food in its own right, there is some evidence that there is not a pro rata increase in potency.

The D⁶-desaturase gene from borage has now been cloned and function has been demonstrated in tobacco. It may therefore prove possible to obtain GLA from a mainstream oil crop, thus potentially reducing the unit cost of GLA by 90-95%. Whilst suitable for the extraction of high- purity GLA for pharmaceutical use, it may be less suitable for the health food market because of consumer concerns and a lack of efficacy in the oil form, as seen with borage. An alternative approach might be to use modern techniques to improve the original sources.