Nervonic acid: Source and Benefits

Introduction

Nervonic acid (C24:1 Δ15, cis-15-tetracosenoic acid, NA) is a very long-chain fatty acid whose name originated from the original discovery in mammalian nerve tissues. Nutrient plays a vital role in human health, especially for the brain. NA combines with sphingosines via an amide bond to form nervonyl sphingolipids, an important component in the white matter of brains and myelinated nerve fibres. NA is closely associated with the development and maintenance of the brain and the biosynthesis and improvement of nerve cells. As a natural component of maternal milk, NA can also promote the growth of infants by assisting their nervous system development[1].

Benefits

It was found that the shark brain could repair itself in a short time after being severely damaged, suggesting the exceptional effect of NA in promoting the repair and regeneration of nerve fibres in damaged brain tissues. NA combines with sphingosines via amide bonds to form nervonyl sphingolipids, chiefly found in nervous and brain tissues, comprising the white matter and myelin sheath of nerve fibres. NA plays a vital role in developing and maintaining the brain and biosynthesizing and improving nerve cells. NA is a natural component of maternal milk and can promote infant growth by assisting nervous system development. Decreased NA levels are closely associated with a high risk of developing psychotic disorders in individuals, and supplementation with NA is an established effective treatment for symptoms of several neurological diseases, such as demyelinating disorders. NA can also function as a non-competitive inhibitor of human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) in a dose-dependent manner. Increasing dietary NA improves energy metabolism in mice and may be an effective strategy for treating obesity-related complications.

Source

The production of NA by microorganisms, which may be an excellent option for mass production, has attracted increasing interest. One way of NA production in the human body is by the conversion from other fatty acids through a series of biochemical reactions; another way is direct ingestion, by which NA is readily available to the body. NA is crucial in pharmacological and nutraceutical applications because of its excellent biofunctions[2].

In the last 60 years, there has been much interest in obtaining new oil-containing plants for industrial and edible purposes. A particular focus has been on NA-containing oil seed plants to explore renewable resources and reduce shark fishing. Thus far, NA has been found in 38 plant species belonging to 31 genera and 13 families, of which eight woody and two herbaceous plants contain at least 4.6% NA. The amounts of NA are affected by genetic factors and various environmental factors, such as planting patterns and growing conditions. Considering the significant differences in the oil and nerve acid content in the seeds of plants, only plants with high oil contents and abundant NA contents are suitable for exploiting and extracting NA. The seed oil content, NA and erucic acid (EA, 22:1) content, and NA production limitations of 10 valuable NA-containing plant species from seven families, including four woody and six herbaceous plants, have been listed and compared in Table 1.

Plants with more than 10% oil content have potential industrial value. As indicated in Table 1, nine of the 10 plant species have oil contents greater than 10%. The high oil content (≥40.1%) is found in the seeds of X. sorbifolia, Ximenia caffra Sond., M. oleifera, and A. truncatum. Given a certain oil content, the ratio of NA to total FAs can best reflect the utilization value of a plant species as a raw material for NA extraction. Eight out of 10 plant species have NA contents greater than 2%. The highest NA content (≥63.0%) is found in M. oleifera, Cardamine graeca L., and Tropaeolum speciosum Poepp seeds. & Endl (T. speciosum). Considering the above two factors, among the 10 plant species, the seeds of M. oleifera, T. speciosum, and Lunaria annua L./Lunaria biennis Moench (L. annua) have both high oil and NA contents and are thus potential candidates for the development of NA products.

Nervonic acid is the major FA in M. oleifera and accounts for 55.7–67.0% of the total FAs in this plant, the oil content of which ranges from 58.0% to 63.0%. M. oleifera has the highest NA content reported thus far in any seed fat. However, M. oleifera is a rare and endangered woody oil plant that grows naturally in western Guangxi and southeast Yunnan in China, and its narrow distribution, in addition to its protected status, limits its development and industrialization. T. speciosum, a unique perennial herbaceous plant species from Chile, has a seed oil content of 12.3∼26.0%, with NA remarkably constituting 40.0∼45.4% of the total FA content. However, its seeds are difficult to obtain and reproduce. L. annua is a biennial herbaceous oil crop considered a niche crop beyond its ornamental value in many countries. The oil content of its seeds is 25%∼35%, with NA accounting for 14.0∼24.2% of the total FA content but with EA constituting up to 50%. The seed yields of L. annua vary greatly (800–2000 kg/ha), and seed shattering and the associated harvesting difficulties are long-standing problems. In addition, due to its high EA content, L. annua oil cannot meet the nutraceutical and pharmaceutical NA oil requirements of a high NA content but very low EA (< 5%) content, as diets rich in EA have toxic effects on the heart.

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