Secologanin

Pictet-Spengler Reaction for the Chemical Synthesis of Strictosidine.[Pubmed:35732938]

Methods Mol Biol. 2022;2505:79-85.

Strictosidine is the common biosynthetic precursor of Monoterpene Indole Alkaloids (MIA). A practical single-step procedure to assemble strictosidine from Secologanin is described via a bioinspired Pictet-Spengler reaction. Mild conditions and purification by crystallization and flash chromatography allow access to the targeted product in fair yield.

Studying Iridoid Transport in Catharanthus roseus by Grafting.[Pubmed:35732937]

Methods Mol Biol. 2022;2505:69-77.

The plant Catharanthus roseus is well known for its spatial separation of iridoid and monoterpenoid indole alkaloid (MIA) biosynthesis at both intracellular and intercellular levels, collectively suggested by RNA in situ hybridization, enzymatic and transcriptomic studies using leaf epidermis, and fluorescent protein tagging studies. Although documented in other plant species, the long-distance transport of iridoid glycosides, such as Secologanin, has not been known in C. roseus until a recent study suggested that Secologanin is transported from root to shoot, by grafting low iridoid/MIA mutant scions onto wild-type stock plants. This chapter describes the in vitro cultivation of C. roseus plants and grafting techniques to enable studies concerning iridoid/MIA transport between organs. The iridoid and MIA analysis methods are also provided.

Enhancement of Vindoline and Catharanthine Accumulation, Antioxidant Enzymes Activities, and Gene Expression Levels in Catharanthus roseus Leaves by Chitooligosaccharides Elicitation.[Pubmed:35323487]

Mar Drugs. 2022 Mar 3;20(3). pii: md20030188.

Catharanthus roseus (L.) G. Don is a plant belonging to the genus Catharanthus of the Apocynaceae family. It contains more than one hundred alkaloids, of which some exhibit significant pharmacological activities. Chitooligosaccharides are the only basic aminooligosaccharides with positively charged cations in nature, which can regulate plant growth and antioxidant properties. In this study, the leaves of Catharanthus roseus were sprayed with chitooligosaccharides of different molecular weights (1 kDa, 2 kDa, 3 kDa) and different concentrations (0.01 mug/mL, 0.1 mug/mL, 1 mug/mL and 10 mug/mL). The fresh weights of its root, stem and leaf were all improved after chitooligosaccharides treatments. More importantly, the chitooligosaccharides elicitor strongly stimulated the accumulation of vindoline and catharanthine in the leaves, especially with the treatment of 0.1 mug/mL 3 kDa chitooligosaccharides, the contents of them were increased by 60.68% and 141.54%, respectively. Furthermore, as the defensive responses, antioxidant enzymes activities (catalase, glutathione reductase, ascorbate peroxidase, peroxidase and superoxide dismutase) were enhanced under chitooligosaccharides treatments. To further elucidate the underlying mechanism, qRT-PCR was used to investigate the genes expression levels of Secologanin synthase (SLS), strictosidine synthase (STR), strictosidine glucosidase (SGD), tabersonine 16-hydroxylase (T16H), desacetoxyvindoline-4-hydroxylase (D4H), deacetylvindoline-4-O-acetyltransferase (DAT), peroxidase 1 (PRX1) and octadecanoid-responsive Catharanthus AP2-domain protein 3 (ORCA3). All the genes were significantly up-regulated after chitooligosaccharides treatments, and the transcription abundance of ORCA3, SLS, STR, DAT and PRX1 reached a maximal level with 0.1 mug/mL 3 kDa chitooligosaccharides treatment. All these results suggest that spraying Catharanthus roseus leaves with chitooligosaccharides, especially 0.1 mug/mL of 3 kDa chitooligosaccharides, may effectively improve the pharmaceutical value of Catharanthus roseus.