Chemical constituents from Flourensia resinosa S.F. Blake (Asteraceae)

Current trends in natural products for the treatment and management of dementia: Computational to clinical studies

The number of preclinical and clinical studies evaluating natural products-based management of dementia has gradually increased, with an exponential rise in 2020 and 2021. Keeping this in mind, we examined current trends from 2016 to 2021 in order to assess the growth potential of natural products in the treatment of dementia. Publicly available literature was collected from various databases like PubMed and Google Scholar. Oxidative stress-related targets, NF-κB pathway, anti-tau aggregation, anti-AChE, and A-β aggregation were found to be common targets and pathways. A retrospective analysis of 33 antidementia natural compounds identified 125 sustainable resources distributed among 65 families, 39 orders, and 7 classes. We found that families such as Berberidaceae, Zingiberaceae, and Fabaceae, as well as orders such as Lamiales, Sapindales, and Myrtales, appear to be important and should be researched further for antidementia compounds. Moreover, some natural products, such as quercetin, curcumin, icariside II, berberine, and resveratrol, have a wide range of applications. Clinical studies and patents support the importance of dietary supplements and natural products, which we will also discuss. Finally, we conclude with the broad scope, future challenges, and opportunities for field researchers.

Eudesmane-type sesquiterpene diols directly synthesized by a sesquiterpene cyclase in Tripterygium wilfordii

Cryptomeridiol, a typical eudesmane diol, is the active principle component of the antispasmodic Proximol. Although it has been used for many years, the biosynthesis pathway of cryptomeridiol has remained blur. Among terpenoid natural products, terpenoid cyclases are responsible for cyclization and generation of hydrocarbon backbones. The cyclization is mediated by carbocationic cascades and ultimately terminated via deprotonation or nucleophilic capture. Isoprene precursors are, respectively, converted into hydrocarbons or hydroxylated backbones. A sesquiterpene cyclase in Tripterygium wilfordii (TwCS) was determined to directly catalyze (E,E)-farnesyl pyrophosphate (FPP) to unexpected eudesmane diols, primarily cryptomeridiol. The function of TwCS was characterized by a modular pathway engineering system in Saccharomyces cerevisiae. The major product determined by NMR spectroscopy turned out to be cryptomeridiol. This unprecedented production was further investigated in vitro, which verified that TwCS can directly produce eudesmane diols from FPP. Some key residues for TwCS catalysis were screened depending on the molecular model of TwCS and mutagenesis studies. As cryptomeridiol showed a small amount of volatile and medicinal properties, the biosynthesis of cryptomeridiol was reconstructed in S. cerevisiae. Optimized assays including modular pathway engineering and the CRISPR–cas9 system were successfully used to improve the yield of cryptomeridiol in the S. cerevisiae. The best engineered strain TE9 (BY4741 erg9::Δ-200-176 rox1::mut/pYX212-IDI + TwCS/p424-tHMG1) ultimately produced 19.73 mg/l cryptomeridiol in a shake flask culture.

Constituents of Flourensia blakeana (Asteraceae)

Chemical study of the aerial parts of Flourensia blakeana Dillon allowed the isolation and identification of two novel compounds, 3, 5, 5'-trihydroxy-7, 3'-dimethoxyflavanone (1), and 2α-angeloyloxycostic acid (2) together with several known compounds. The structures were elucidated using spectroscopic data from 1D, 2D NMR and HRDEIMS experiments.

Dysosesquiflorins A and B, sesquiterpenoids from Dysoxylum densiflorum

Two new aromadendrane sesquiterpenoids, dysosesquiflorins A and B (1 and 2), were isolated from Dysoxylum densiflorum bark, and their structures were elucidated on the basis of NMR spectroscopic data. These dysosesquiflorins showed in vitro cytotoxic activity against several cancer cell lines.