Glycosylation of Capsaicin Derivatives and Phenylpropanoid Derivatives Using Cultured Plant Cells

Plant cell cultures: An enzymatic tool for polyphenolic and flavonoid transformations

BACKGROUND

In the pharmaceutical sector, tissue culture techniques for large-scale production of natural chemicals can be a less expensive alternative to large-scale synthesis. Although recent biotransformation research have used plant cell cultures to target a wide range of bioactive compounds, more compiled information and synopses are needed to better understand metabolic pathways and improve biotransformation efficiencies.

PURPOSE

This report reviews the biochemical transformation of phenolic natural products by plant cell cultures in order to identify potential novel biotechnological approaches for ensuring more homogeneous and stable phenolic production year-round under controlled environmental conditions.

METHODS

Articles on the use of plant cell culture for polyphenolic and flavonoid transformations (1988 - 2021) were retrieved from SciFinder, PubMed, Scopus, and Web of Science through electronic and manual search in English. Following that, the authors chose the required papers based on the criteria they defined. The following keywords were used for the online search: biotransformation, Plant cell cultures, flavonoids, phenolics, and pharmaceutical products.

RESULTS

The initial search found a total of 96 articles. However, only 70 of them were selected as they met the inclusion criteria defined by the authors. The analysis of these studies revealed that plant tissue culture is applicable for the large-scale production of plant secondary metabolites including the phenolics, which have high therapeutic value.

CONCLUSION

Plant tissue cultures could be employed as an efficient technique for producing secondary metabolites including phenolics. Phenolics possess a wide range of therapeutic benefits, as anti-oxidant, anti-cancer, and anti-inflammatory properties. Callus culture, suspension cultures, transformation, and other procedures have been used to improve the synthesis of phenolics. Their production on a large scale is now achievable. More breakthroughs will lead to newer insights and, without a doubt, to a new era of phenolics-based pharmacological agents for the treatment of a variety of infectious and degenerative disorders.

Structural basis for substrate recognition in the Phytolacca americana glycosyltransferase PaGT3

Capsaicinoids are phenolic compounds that have health benefits. However, the pungency and poor water solubility of these compounds limit their exploitation. Glycosylation is a powerful method to improve water solubility and reduce pungency while preserving bioactivity. PaGT3, a uridine diphosphate glycosyltransferase (UGT) from Phytolacca americana, is known for its ability to glycosylate capsaicinoids and other phenolic compounds. While structural information on several UGTs is available, structures of UGTs that can glycosylate a range of phenolic compounds are rare. To fill this gap, crystal structures of PaGT3 with a sugar-donor analogue (UDP-2-fluoroglucose) and the acceptors capsaicin and kaempferol were determined. PaGT3 adopts a GT-B-fold structure that is highly conserved among UGTs. However, the acceptor-binding pocket in PaGT3 is hydrophobic and large, and is surrounded by longer loops. The larger acceptor-binding pocket in PaGT3 allows the enzyme to bind a range of compounds, while the flexibility of the longer loops possibly plays a role in accommodating the acceptors in the binding pocket according to their shape and size. This structural information provides insights into the acceptor-binding mechanism in UGTs that bind multiple substrates.

Ferulic Acid Esters of Oligo-glucose from Allium macrostemon

Two new ferulic acid esters of oligo-glucose, 1- O- (E)-feruloyl-β-D-gentiobioside (1) and 1- O-( E)-feruloyl-{β-D-glucopyranosyl (1→6)-[β-D-glucopyranosyl (1→2)]}-β-D-glucopyranoside (allimacronoid D, 2) were isolated together with 1- O-( E)-feruloyl-β-D-glucopyranoside (3) and trans-ferulic acid (4) from the leaves of Allium macrostemon Bunge. The chemical structures were elucidated based on the analyses of the spectroscopic and chemical data.

(1) H and (13) C NMR data on natural and synthetic capsaicinoids

Capsaicinoids are the compounds responsible for the pungency of chili peppers. These substances have attracted the attention of many research groups in recent decades because of their antinociceptive, analgesic, anti-inflammatory, and anti-obesity properties, among others. There are nearly 160 capsaicinoids reported in the literature. Approximately 25 of them are natural products, while the rest are synthetic or semi-synthetic products. A large amount of NMR data for the capsaicinoids is dispersed throughout literature. Therefore, there is a need to organize all this NMR data in a systematic and orderly way. This review summarizes the (1) H and (13) C NMR data on 159 natural and synthetic capsaicinoids, with a brief discussion of some typical and relevant aspects of these NMR data. Copyright © 2015 John Wiley & Sons, Ltd.

Biotransformation of 21-O-acetyl-deoxycorticosterone by cell suspension cultures of Digitalis lanata (strain W.1.4)

Cell cultures of Digitalis species are known to accept exogenous substrates for biotransformation reactions. We here report the biotransformation of 21-O-acetyl-deoxycorticosterone (1) by cell suspension cultures of Digitalis lanata strain W.1.4. Nine derivatives of 1 were obtained and their chemical structures determined by spectroscopic methods. 2β-Hydroxylation and C-21-glucosylation of the steroidal nucleus were described for the first time in suspension-cultured plant cells. Steroid 5α- and 5β-reduction products were also observed. Among the compounds isolated and structures elucidated were 2β,3β,21-trihydroxy-4-pregnen-20-one, 2β,3α,21-trihydroxy-4-pregnen-20-one and 3β,21-dihydroxy-5α-pregnan-20-one-3β-O-β-glucoside.