Plant specialized metabolism serves as a rich resource of biologically active molecules for drug discovery. The acylated flavonol glycoside montbretin A (MbA) and its precursor myricetin 3--(6'--caffeoyl)-glucosyl rhamnoside (mini-MbA) are potent inhibitors of human pancreatic α-amylase and are being developed as drug candidates to treat type-2 diabetes. MbA occurs in corms of the ornamental plant montbretia (), but a system for large-scale MbA production is currently unavailable. Biosynthesis of MbA from the flavonol myricetin and MbA accumulation occur during early stages of corm development. We established myricetin 3--rhamnoside (MR), myricetin 3--glucosyl rhamnoside (MRG), and mini-MbA as the first three intermediates of MbA biosynthesis. Contrasting the transcriptomes of young and old corms revealed differentially expressed UDP-sugar-dependent glycosyltransferases (UGTs) and BAHD-acyltransferases (BAHD-ATs). UGT77B2 and UGT709G2 catalyze the consecutive glycosylation of myricetin to produce MR and of MR to give MRG, respectively. In addition, two BAHD-ATs, CcAT1 and CcAT2, catalyze the acylation of MRG to complete the formation of mini-MbA. Transcript profiles of UGT77B2, UGT709G2, CcAT1, and CcAT2 during corm development matched the metabolite profile of MbA accumulation. Expression of these enzymes in wild tobacco () resulted in the formation of a surrogate mini-MbA, validating the potential for metabolic engineering of mini-MbA in a heterologous plant system.

Monoterpene indole alkaloids (MIAs) are a diverse class of plant natural products that include a number of medicinally important compounds. We set out to reconstitute the pathway for strictosidine, a key intermediate of all MIAs, from central metabolism in Nicotiana benthamiana. A disadvantage of this host is that its rich background metabolism results in the derivatization of some heterologously produced molecules. Here we use transcriptomic analysis to identify glycosyltransferases that are upregulated in response to biosynthetic intermediates and produce plant lines with targeted mutations in the genes encoding them. Expression of the early MIA pathway in these lines produces a more favorable product profile. Strictosidine biosynthesis was successfully reconstituted, with the best yields obtained by the co-expression of 14 enzymes, of which a major latex protein-like enzyme (MLPL) from Nepeta (catmint) is critical for improving flux through the iridoid pathway. The removal of endogenous glycosyltransferases does not impact the yields of strictosidine, highlighting that the metabolic flux of the pathway enzymes to a stable biosynthetic intermediate minimizes the need to engineer the endogenous metabolism of the host. The production of strictosidine in planta expands the range of MIA products amenable to biological synthesis.

Monoterpene indole alkaloids (MIAs) are a diverse and important class of plant natural products that include a number of medicinally significant compounds, often present at low concentrations within their native plant species. The complex biosynthesis of MIAs requires the assembly of tryptamine with a secoiridoid to produce the central intermediate, strictosidine, from which all known MIAs derive. Structural complexity makes chemical synthesis challenging, but recent efforts to identify the biosynthetic enzymes provide options for pathway reconstruction in a heterologous host. Previous attempts have had limited success, with yield in microorganisms limited by the poor expression of some enzymes. Here, we reconstitute the pathway for strictosidine biosynthesis from central metabolism without the need for supplementation of any metabolite precursors or intermediates in Nicotiana benthamiana. The best yields were obtained by the co-expression of 14 enzymes, of which a major latex protein-like enzyme (MLPL) from Nepeta (catmint) was critical for improving flux through the secoiridoid pathway. The production of strictosidine in planta expands the range of MIA products amenable to biological synthesis.

4-Aryl-2-quinolones are important skeletons from both chemical and medicinal viewpoints. We herein report the development of an efficient synthetic method for 3-substituted 4-aryl-2-quinolones. The key reaction in this process involves an AlCl3-mediated intramolecular cyclization of substituted 2-(carbamoyl)-3-phenylacrylates, with optimized reaction conditions of 2.0 equivalents of AlCl3, nitrobenzene, 80 °C, and 3 hours. The chemical yields of cyclization were found to be sensitive to all reaction conditions.

Background/Aims: A previous study showed that dietary intervention with Artemisia and green tea extracts, i.e., SD1003F, relieved Helicobacter pylori-associated chronic atrophic gastritis in a mouse model. We continue the research through the current randomized double-blind clinical trial to evaluate the efficacy and safety of the intervention for H. pylori-associated gastric discomfort. Materials and Methods:Forty-nine volunteers who tested positive for H. pylori infection received either placebo or SD1003F for 10 weeks and their functional dyspepsia-related quality of life (QOL) was evaluated. H. pylori infection using a urea breath test (UBT), measurement of pepsinogen level using GastroPanel. Adverse effects with biochemical changes were also evaluated. Results: SD1003F administration significantly improved health related-QOL, including dietary intake, emotional stability, life pattern, and social factors relevant to gastric discomfort, in comparison to the control (P＜0.05). The mean UBT measurement significantly decreased in the SD1003F group (P＜0.05). In 2 of the 24 volunteers, SD1003F alone eradicated H. pylori infection, with significant improvements in endoscopic findings. GastroPanel analysis revealed significant improvements that reflect rejuvenation of gastric atrophy in the SD1003F group. No significant side effect was observed in any participant. Conclusions: SD1003F (Artemisia and green tea extract), is a potential phytochemical to improve H. pylori-associated gastric discomfort. (Korean J Helicobacter Up Gastrointest Res 2018;18:38-49)

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