Flavonoids as Sirtuin Modulators.

Sirtuins (SIRTs) are described as NAD+-dependent deacetylases, also known as class III histone deacetylases. So far, seven sirtuin genes (SIRTS 1-7) have been identified and characterized in mammals and are also known to occur in bacteria and eukaryotes. SIRTs are involved in various biological processes, including endocrine system, apoptosis, aging and longevity, diabetes, rheumatoid arthritis, obesity, inflammation, etc. Among them, the best-characterized one is SIRT1. Small molecules seem to be the most effective SIRT modulators. Flavonoids have been reported to possess many positive effects favorable for human health, while relatively less research has been reported so far on their functions as SIRT modulation mechanisms. In this regard, we aimed to focus on the modulatory effects of flavonoids on SIRTs as the most common secondary metabolites in natural products. Our literature survey covering the years from 2006 to 2021 pointed out that flavonoids frequently interact with SIRT1 and SIRT3, followed by SIRT6. It can also be concluded that some popular flavonoid derivatives, eg., resveratrol, quercetin, and catechin derivatives, came forward in terms of SIRT modulation.

Reinvestigation of Herniaria glabra L. saponins and their biological activity.

Twelve undescribed triterpenoid pentacyclic glycosides, medicagenic acid (3-O-ß-D-glucuronopyranosyl-28-O-{[ß-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 3)]-4-O-acetyl-ß-D-fucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-12-ene-23,28-dioic acid, 3-O-ß-D-glucuronopyranosyl-28-O-{[α-L-rhamnopyranosyl-(1 → 2)]-[ß-D-apiofuranosyl-(1 → 3)]-4-O-acetyl-ß-D-fucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-12-ene-23,28-dioic acid, 3-O-ß-D-glucuronopyranosyl-28-O-{[α-L-rhamnopyranosyl-(1 → 2)]-3,4-O-diacetyl-ß-D-fucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[6-O-acetyl-ß-D-glucopyranosyl-(1 → 2)]-[2-O-acetyl-α-L-rhamnopyranosyl-(1 → 4)-ß-D-glucopyranosyl-(1 → 6)]-ß-D-glucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[6-O-acetyl-ß-D-glucopyranosyl-(1 → 2)]-[3-O-acetyl-α-L-rhamnopyranosyl-(1 → 4)-ß-D-glucopyranosyl-(1 → 6)]-ß-D-glucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[6-O-acetyl-ß-D-glucopyranosyl-(1 → 2)]-[4-O-acetyl-α-L-rhamnopyranosyl-(1 → 4)-ß-D-glucopyranosyl-(1 → 6)]-ß-D-glucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[6-O-acetyl-ß-D-glucopyranosyl-(1 → 2)]-[ß-D-glucopyranosyl-(1 → 6)]-ß-D-glucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[ß-D-glucopyranosyl-(1 → 2)]-[ß-D-glucopyranosyl-(1 → 6)]-ß-D-glucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-12-ene-23,28-dioic acid), zanhic acid (3-O-ß-D-glucuronopyranosyl-28-O-{[ß-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 3)]-4-O-acetyl-ß-D-fucopyranosyl-(1→)}2ß,3ß,16α-trihydroxyolean-12-ene-23,28-dioic acid, 3-O-ß-D-glucuronopyranosyl-28-O-{[ß-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-ß-D-fucopyranosyl-(1→)}-2ß,3ß,16α-trihydroxyolean-12-ene-23,28-dioic acid), 29-hydroxy-medicagenic acid (3-O-ß-D-glucuronopyranosyl-28-O-{[ß-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 3)]-4-O-acetyl-ß-D-fucopyranosyl-(1→)}-2ß,3ß,29ß-trihydroxyolean-12-ene-23,28-dioic acid) and herniaric acid (28-O-{[6-O-acetyl-ß-D-glucopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 4)-ß-D-glucopyranosyl-(1 → 6)]-ß-D-glucopyranosyl-(1→)}-2ß,3ß-dihydroxyolean-18-ene-23,28-dioic acid) were isolated from the whole plant extract of Herniaria glabra L. (Caryophyllaceae), wild growing in the Ukraine. In addition, five known triterpenoid saponins; i.e. herniariasaponins 1, 4, 5, 6, and 7 were also isolated. Their structures were elucidated by HRESIMS, 1D and 2D NMR spectroscopy, as well as by comparison with the literature data. Twelve herniariasaponins, the purified crude extract, and the saponin fraction were evaluated in vitro for their xanthine oxidase, collagenase, elastase, and tyrosinase inhibitory activity. Moreover, herniariasaponins 4, 5, and 7 were screened for their cholinesterase inhibitory potential. As a result, no or low inhibition towards the mentioned enzymes was observed.

Yuccalechins A-C from the Yucca schidigera Roezl ex Ortgies Bark: Elucidation of the Relative and Absolute Configurations of Three New Spirobiflavonoids and Their Cholinesterase Inhibitory Activities.

The ethyl acetate fraction of the methanolic extract of Yucca schidigera Roezl ex Ortgies bark exhibited moderate acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity (IC50 47.44 and 47.40 µg mL-1, respectively). Gel filtration on Sephadex LH-20 and further RP-C18 preparative HPLC of EtOAc fraction afforded 15 known and 3 new compounds, stereoisomers of larixinol. The structures of the isolated spirobiflavonoids 15, 26, and 29 were elucidated using 1D and 2D NMR and MS spectroscopic techniques. The relative configuration of isolated compounds was assigned based on coupling constants and ROESY (rotating-frame Overhauser spectroscopy) correlations along with applying the DP4+ probability method in case of ambiguous chiral centers. Determination of absolute configuration was performed by comparing calculated electronic circular dichroism (ECD) spectra with experimental ones. Compounds 26 and 29, obtained in sufficient amounts, were evaluated for activities against AChE and BChE, and they showed a weak inhibition only towards AChE (IC50 294.18 µM for 26, and 655.18 µM for 29). Furthermore, molecular docking simulations were performed to investigate the possible binding modes of 26 and 29 with AChE.

High-performance counter-current chromatography isolation and initial neuroactivity characterization of furanocoumarin derivatives from Peucedanum alsaticum L (Apiaceae).

BACKGROUND: Medicinal plants are a proven source of drug-like small molecules with activity towards targets relevant for diseases of the central nervous system (CNS). Plant species of the Apiaceae family have to date yielded a number of neuroactive metabolites, such as coumarin derivatives with acetylcholinesterase inhibitory activity or anti-seizure activity. PURPOSE: To accelerate the discovery of neuroactive phytochemicals with potential as CNS drug leads, we sought to rapidly isolate furanocoumarins, primary constituents of the dichloromethane (DCM) extract of the fruits of Peucedanum alsaticum L. (Apiaceae), using high-performance counter-current chromatography (HPCCC) and to evaluate their neuroactivity using both in vitro and in vivo microscale bioassays based on cholinesterase ELISAs and zebrafish epilepsy models. RESEARCH METHODS AND PROCEDURE: In this study the DCM extract was subjected to HPCCC for the efficient separation (60 min) and isolation of furanocoumarins. Isolated compounds were identified with TOF-ESI-MS and NMR techniques and examined as inhibitors of AChE and BChE using ELISA microtiter assays. Anti-seizure properties of the extract and of the isolated compounds were evaluated using a zebrafish epilepsy model based on the GABAA antagonist pentylenetetrazol (PTZ), which induces increased locomotor activity and seizure-like behavior. RESULTS: The solvent system, composed of n-heptane, ethyl acetate, methanol and water (3:1:3:1, v/v/v/v), enabled the isolation of 2.63 mg lucidafuranocoumarin A (purity 98%) and 8.82 mg bergamottin (purity 96%) from 1.6 g crude DCM extract. The crude extract, at a concentration of 100 µg/ml, exhibited a weak inhibitory activity against acetylcholinesterase (AChE) (9.63 ±â€¯1.59%) and a moderate inhibitory activity against butyrylcholinestrase (BChE) (49.41 ±â€¯2.19%). Lucidafuranocoumarin A (100 µg/ml) was inactive against AChE but showed moderate inhibition towards BChE (40.66 ±â€¯1.25%). The DCM extract of P. alsaticum fruits (0.62-1.75 µg/ml) and bergamottin (2-10 µm) exhibited weak anti-seizure activity, while lucidafuranocoumarin A (10-16 µm) was found to significantly inhibit PTZ-induced seizures. The percentage of seizure inhibition for the isolated compounds, at their most bioactive concentration, was 26% for bergamottin and 69% for lucidafuranocoumarin A. CONCLUSION: Our findings underscore the utility of HPCCC for the rapid isolation of rare coumarin derivatives, and the potential of microscale in vivo bioassays based on zebrafish disease models for the rapid assessment of neuroactivity of these drug-like natural products.