Biosynthesis of Indole alkaloids

Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined together to form macromolecules. This process often consists of metabolic pathways.

Biosynthesis. Biogenetic precursor of all indole alkaloids is the amino acid tryptophan. For most of them, the first synthesis step is decarboxylation of tryptophan to form tryptamine. Dimethyltryptamine (DMT) is formed from tryptamine by methylation with the participation of coenzyme of S-adenosyl methionine (SAM).

Tryptamine and secologanin are condensed to form strictosidine, which is the common precursor of all indole alkaloids. Strictosidine is deglucosylated and then converted to ajmalicine, catharanthine, vindoline, and other indole alkaloids.

Two plants that contain indole alkaloids are Passiflora incarnata L. (passion flower) and Mitragyna speciosa (Korth.) Havil (kratom), while the other two plants that did not show the presence of indole alkaloids are Piper methysticum G. Forst (kava) and Valeriana officinalis L., deserve special attention.

There are four steps that are typically present in the first steps of complex alkaloid biosynthesis: (i) accumulation of an amine precursor, (ii) accumulation of an aldehyde precursor, (iii) formation of an iminium cation and (iv) a Mannich-like reaction!

Certain plant families are particularly rich in alkaloids; all plants of the poppy family (Papaveraceae) are thought to contain them, for example. The Ranunculaceae (buttercups), Solanaceae (nightshades), and Amaryllidaceae (amaryllis) are other prominent alkaloid-containing families.

Important indole alkaloids which have been isolated from plants include the antihypertensive drug, reserpine from Rauvolfia serpentina (Sagi et al., 2016) and the powerful antitumor drugs, vinblastine and vincristine from Catharanthus roseus (El-Sayed and Verpoorte, 2007).