Synthesis of Coumestrol and Aureol

Four new compounds isolated from the rhizomes of Phedimus aizoon (L.) 't Hart

One new coumarin, one new flavonoid, two new distinctive compounds with characteristics of an iriflophene unit and a flavonoid unit connecting via a furan ring, together with five known compounds were isolated from the rhizomes of Phedimus aizoon (L.) 't Hart. Their structures were elucidated on the basis of spectroscopic analysis. Compounds 4, 5 and 8 increased the survival rate of H9c2 cells induced by doxorubicin in vitro, which was capable of further drug exploration.

Mass Biosynthesis of Coumestrol Derivatives and Their Isomers via Soybean Adventitious Root Cultivation in Bioreactors

Coumestrol (CMS) derivatives are unique compounds, which function as phytoalexins; they are derived from soybean roots, following abiotic and biotic stresses. As a phytoalexin, CMS forms a defense system that enables plants to maintain their viability. However, it is still challenging to achieve the mass production of phytoalexins, which exhibit pharmacological values, via plant breeding. Here, the synthesis of CMS derivatives from the seedling, plant, and adventitious root (AR) of Glycine max were investigated under artificial light, as well as via a chemical elicitor treatment. In the presence of constant light, as well as under treatment with methyl jasmonate, the CMS monoglucoside (coumestrin; CMSN) and malonyl CMSN (M-CMSN) contents of the AR culture (4 weeks) increased drastically. The two CMS derivatives, CMSN and M-CMSN, were obtained as a mixture of isomers, which were identified via nuclear magnetic resonance analysis. These derivatives were also observed in a soybean plant that was grown on artificial soil (AS; 5 weeks) and a Petri dish (9 days) although in considerably lesser quantities than those observed in the AR culture. Compared with the two other media (AS and the Petri dish), the AR culture achieved the superior synthesis of CMSN and M-CMSN within a relatively short cultivation period (<1 month) in laboratory-scale (3 L) and pilot-scale (1,000 L) bioreactors. The isoflavone content of AR under the constant light conditions was three-fold that under dark conditions. Significant quantities of malonyl daidzin and malonyl genistin were produced in the root of AS and the seedling of Petri dish, respectively. Flavonol glycosides were not produced in the AR culture under the dark and light conditions, as well as in AS under the dark condition. However, significant contents of kaempferol glycosides were produced in the leaves of AS and seedling of Petri dish, following the light treatment. Thus, we proposed that the established soybean AR-cultivation approach represented a better method for biosynthesizing phytoalexins, such as the CMS derivatives, as plant-derived functional materials.

Design, synthesis, and physicochemical study of a biomass-derived CO2 sorbent 2,5-furan-bis(iminoguanidine)

In this study, the concept of biomass-based direct air capture is proposed, and the aminoguanidine CO2 chemical sorbent 2,5-furan-bis(iminoguanidine) (FuBIG) was designed, synthesized, and elucidated for the physicochemical properties in the process of CO2 capture and release. Results showed that the aqueous solution of FuBIG could readily capture CO2 from ambient air and provided an insoluble tetrahydrated carbonate salt FuBIGH2(CO3) (H2O)4 with a second order kinetics. Hydrogen binding modes of iminoguanidine cations with carbonate ions and water were identified by single-crystal X-ray diffraction analysis. Equilibrium constant (K) and the enthalpies (ΔH) for CO2 absorption/release were obtained by thermodynamic and kinetic analysis (K7 = 5.97 × 104, ΔH7 = -116.1 kJ/mol, ΔH8 = 209.31 kJ/mol), and the CO2-release process was conformed to the geometrical phase-boundary model (1-(1-α)1/3 = kt). It was found that the FuBIGH2(CO3) (H2O)4 can release CO2 spontaneously in DMSO without heating. Zebrafish models revealed a favorable biocompatibility of FuBIG.

Naturally occurring coumestans from plants, their biological activities and therapeutic effects on human diseases

Naturally occurring coumestans are known as a collection of plant-derived polycyclic aromatic secondary metabolites which are characterized by the presence of an oxygen heterocyclic four-ring system comprising a coumarin moiety and a benzofuran moiety sharing a C˭C bond. Recently, there is an increasing attention in excavating the medicinal potential of coumestans, particularly coumestrol, wedelolactone, psoralidin and glycyrol, in a variety of diseases. This review is a comprehensive inventory of the chemical structures of coumestans isolated from various plant sources during the period of 1956-2020, together with their reported biological activities. 120 molecules were collected and further classified as coumestans containing core skeleton, dimethylpyranocoumestans, furanocoumestans, O-glycosylated coumestans and others, which showed a wide range of pharmacological activities including estrogenic, anti-cancer, anti-inflammatory, anti-osteoporotic, organ protective, neuroprotective, anti-diabetic and anti-obesity, antimicrobial, immunosuppressive, antioxidant and skin-protective activities. Furthermore, this review focuses on the counteraction of coumestans against bone diseases and organ damages, and the involved molecular mechanisms, which could provide important information to better understand the medicinal values of these compounds. This review is intended to be instructive for the rational design and development of less toxic and more effective drugs with a coumestan scaffold.

Copper-catalyzed intramolecular cross dehydrogenative coupling approach to coumestans from 2'-hydroxyl-3-arylcoumarins

A copper-catalyzed intramolecular cross dehydrogenative C-O coupling reaction of 2'-hydroxyl-3-arylcoumarins was developed. This protocol provided a facile and efficient strategy for the construction of natural coumestans and derivatives in moderate to high yields. This transformation exhibited good functional group compatibility and was amenable to substrates with free phenolic hydroxyl groups.

Inhibitory Properties of ATP-Competitive Coumestrol and Boldine Are Correlated to Different Modulations of CK2 Flexibility

Casein kinase 2 (CK2) is an anti-apoptotic cancer-sustaining protein kinase. Its crystallographic structures with the natural compounds coumestrol, a phytoestrogen, and boldine, an alkaloid, are reported. Coumestrol shows different inhibitory activity against the isolated catalytic α-subunit and the α₂β₂ holoenzyme and is able to discriminate between two conformations of the hinge/αD region, whose intrinsic flexibility is a relevant selectivity determinant among kinases. Boldine explores a small cavity at the bottom of the ATP-binding pocket through a local deviation from planarity, a unique case among CK2 inhibitors. The two compounds have different impacts on protein flexibility, which correlate with their different properties.

3, 9-di-O-substituted coumestrols incorporating basic amine side chains act as novel apoptosis inducers with improved pharmacological selectivity

There is much interest in the use of phytoestrogens such as coumestrol in breast cancer intervention due to their antiestrogenic activity and multiple modes of tumor cell death. However, the clear beneficial effects of naturally occurring estrogen mimetic coumestrol remain controversial due to experimental evidence that it has been shown to stimulate MCF-7 cell proliferation via agonist effect on estrogen receptor at low concentration. Herein, to disconnect the ER interaction and apoptosis-specific mechanism of coumestrol, various 3, 9-di-O-substituted coumestrols (7a-7e) and their furan ring-opened analogs (5a-5e) were synthesized and assessed for antiproliferative properties. Attachment of a dimethylamine-containing side chain to 3-O of coumestrol led to the most promising compound 7e with improved antiproliferative activity (1.7-fold increase) against MCF-7 cells, decreased estrogen activity (>20 times weaker ERα binder) and a novel action to induce apoptosis. Mechanistic studies revealed that 7e is a tubulin polymerization inhibitor, which could arrest cell cycle at G2/M phase and induce apoptosis along with the decrease of mitochondrial membrane potential. In summary, such subtle modifications to the 3, 9-di-hydroxyl groups of coumestrol allow the generation of a novel apoptosis inducer with distinct pharmacological properties, providing an excellent starting point to future development of novel tumor-vascular disrupting agents targeting tubulin.

One-pot two-step synthesis of 3-iodo-4-aryloxy coumarins and their Pd/C-catalyzed annulation to coumestans

An efficient protocol for the synthesis of various coumestans from the intramolecular annulation of 3-iodo-4-aryloxy coumarins through C–H activation has been developed.

An unprecedented tandem synthesis of fluorescent coumarin-fused pyrimidines via copper-catalyzed cross-dehydrogenative C(sp3)–N bond coupling

A Cu-catalyzed tandem strategy for the synthesis of coumarin-fused pyrimidin-5-ones involving in situ intramolecular cross-dehydrogenative C(sp³)–N bond formation.