Tilting Plant Metabolism for Improved Metabolite Biosynthesis and Enhanced Human Benefit

Abstract

The immense chemical diversity of plant-derived secondary metabolites coupled with their vast array of biological functions has seen this group of compounds attract considerable research interest across a range of research disciplines. Medicinal and aromatic plants, in particular, have been exploited for this biogenic pool of phytochemicals for products such as pharmaceuticals, fragrances, dyes, and insecticides, among others. With consumers showing increasing interests in these products, innovative biotechnological techniques are being developed and employed to alter plant secondary metabolism in efforts to improve on the quality and quantity of specific metabolites of interest. This review provides an overview of the biosynthesis for phytochemical compounds with medicinal and other related properties and their associated biological activities. It also provides an insight into how their biosynthesis/biosynthetic pathways have been modified/altered to enhance production.

Keywords: bioactivity; biosynthesis; metabolism; plant secondary metabolite.

Figure 1

A simplified general overview of the biosynthetic pathways involved in the biosynthesis of secondary metabolites showing a tight association with the product of primary/central metabolism. Pink boxes represent secondary metabolites while primary metabolites are without boxes. The pathways in unshaded boxes represent secondary metabolism and the one shaded grey is part of the primary metabolism (most not shown).

Figure 2

A few representative structures of the tropane and nicotine alkaloids.

Figure 3

A few representative structures of the Amaryllidaceae group of alkaloids.

Figure 4

Examples of plant-derived bioactive terpenoid indole alkaloids.

Figure 5

Examples of the members of the plant-derived purine group of alkaloids.

Figure 6

(A) Chemical structure of a proanthocyanidin consisting of the catechin and epicatechin polymeric units, where “n” is any number that makes up the polymer; (B) Generic structure of a flavonoid. Kaempferol, R1 = H, R2 = H; quercetin, R1 = OH, R2 = H; myricetin, R1 = OH, R2 = OH.

Figure 7

A few bioactive examples of the terpenoid group of plant derived secondary metabolites.