Plant cyclopeptides and possible biosynthetic mechanisms.

Plant cyclopeptides are a large group of small molecular weight natural products, typically with 4-10 amino acids, isolated from the leaves, stem barks, roots, and seeds of a wide variety of plant species throughout the world. The peptides are present in many Chinese medicinal plants, and their potentials have not been well exploited because of the lack of knowledge in their biosynthetic origin and mechanism. The cyclopeptides often have complex chemical structures distinct from common polypeptides (proteins) that are non-cyclic and gene-coded. This review discussed the potential origin of the cyclopeptides and their possible biosynthetic mechanisms.