Current Status and De Novo Synthesis of Anti-Tumor Alkaloids in Nicotiana

Abstract

Alkaloids are the most diversified nitrogen-containing secondary metabolites, having antioxidant and antimicrobial properties, and are extensively used in pharmaceuticals to treat different types of cancer. Nicotiana serves as a reservoir of anti-cancer alkaloids and is also used as a model plant for the de novo synthesis of various anti-cancer molecules through genetic engineering. Up to 4% of the total dry weight of Nicotiana was found to be composed of alkaloids, where nicotine, nornicotine, anatabine, and anabasine are reported as the dominant alkaloids. Additionally, among the alkaloids present in Nicotiana, β-carboline (Harmane and Norharmane) and Kynurenines are found to show anti-tumor effects, especially in the cases of colon and breast cancers. Creating new or shunting of existing biosynthesis pathways in different species of Nicotiana resulted in de novo or increased synthesis of different anti-tumor molecules or their derivatives or precursors including Taxadiane (~22.5 µg/g), Artemisinin (~120 μg/g), Parthenolide (~2.05 ng/g), Costunolide (~60 ng/g), Etoposide (~1 mg/g), Crocin (~400 µg/g), Catharanthine (~60 ng/g), Tabersonine (~10 ng/g), Strictosidine (~0.23 mg/g), etc. Enriching the precursor pool, especially Dimethylallyl Diphosphate (DMAPP), down-regulating other bi-product pathways, compartmentalization or metabolic shunting, or organelle-specific reconstitution of the precursor pool, might trigger the enhanced accumulation of the targeted anti-cancer alkaloid in Nicotiana.

Advances in Metabolic Engineering of Plant Monoterpene Indole Alkaloids

“…Several classes of plant natural products have been successfully manufactured in N. benthamiana , such as lignan derived etoposide [ 75 ], betalains [ 76 ], and polyketides [ 77 ]. Due to the remarkable versatility of the metabolism, matched with the compartmentalization necessary for the reconstitution of functional pathways, the short life cycle, and the amenability to Agrobacterium-mediated transient expression, N. benthamiana is an ideal chassis for manufacturing specialized plant metabolites, including MIAs [ 78 , 79 ]. This well-established heterologous system provides additional flexibility in the expression of plant biosynthetic genes from other species, therefore creating potential for manufacturing high-value compounds on an industrial scale.…”

“…Various methods for the de novo synthesis of plant natural product pathways have also been developed. They include infiltration with a strain of Agrobacterium tumefaciens harboring the gene of interest in a plant expression vector by using syringe or vacuum infiltration, virus-mediated overexpression, gene silencing, gene editing, or nuclear/plastid transformation [ 50 , 54 , 78 , 79 ]. Considering that subcellular compartmentalization in monoterpene biosynthesis relies on GPP availability in plastids, cytosol, or mitochondria, N. benthamiana is suitable for the reconstitution of complex MIA biosynthetic pathways, possibly by enriching the pools of MIA precursors [ 80 ].…”

Spectrophotometric and Chromatographic Determination of Alkaloids and Nicotine Contents in Lebanese Tobacco Leaves

“…Among the two thousand five hundred secondary metabolites (Habib et al, 2023) present in N. tabacum, alkaloids are the predominant and quintessential responsible for its potential biological activities. These alkaloids occur predominantly in leaves with a total alkaloid concentration of 0.2 and 8% where the potent compound; Nicotine (NCT) occupies the primary alkaloids and identifies about 90-95% of the total alkaloids (Lewis et al, 2010;Shoji et al, 2010;Sun et al, 2018).…”