The investigation of the constituents that were isolated from Turnera diffusa (damiana) for their inhibitory activities against recombinant human monoamine oxidases (MAO-A and MAO-B) in vitro identified acacetin 7-methyl ether as a potent selective inhibitor of MAO-B (IC50 = 198 nM). Acacetin 7-methyl ether (also known as 5-hydroxy-4′, 7-dimethoxyflavone) is a naturally occurring flavone that is present in many plants and vegetables. Acacetin 7-methyl ether was four-fold less potent as an inhibitor of MAO-B when compared to acacetin (IC50 = 50 nM). However, acacetin 7-methyl ether was >500-fold selective against MAO-B over MAO-A as compared to only two-fold selectivity shown by acacetin. Even though the IC50 for inhibition of MAO-B by acacetin 7-methyl ether was ~four-fold higher than that of the standard drug deprenyl (i.e., SelegilineTM or ZelaparTM, a selective MAO-B inhibitor), acacetin 7-methyl ether’s selectivity for MAO-B over MAO-A inhibition was greater than that of deprenyl (>500- vs. 450-fold). The binding of acacetin 7-methyl ether to MAO-B was reversible and time-independent, as revealed by enzyme-inhibitor complex equilibrium dialysis assays. The investigation on the enzyme inhibition-kinetics analysis with varying concentrations of acacetin 7-methyl ether and the substrate (kynuramine) suggested a competitive mechanism of inhibition of MAO-B by acacetin 7-methyl ether with Ki value of 45 nM. The docking scores and binding-free energies of acacetin 7-methyl ether to the X-ray crystal structures of MAO-A and MAO-B confirmed the selectivity of binding of this molecule to MAO-B over MAO-A. In addition, molecular dynamics results also revealed that acacetin 7-methyl ether formed a stable and strong complex with MAO-B. The selective inhibition of MAO-B suggests further investigations on acacetin 7-methyl as a potential new drug lead for the treatment of neurodegenerative disorders, including Parkinson’s disease.

https://www.mdpi.com/1420-3049/24/4/810/pdf

Selective Inhibition of Human Monoamine Oxidase B by Acacetin 7-Methyl Ether Isolated from Turnera diffusa (Damiana)

Acacetin, a dietary component, is abundant in acacia honey and has superior anticancer activities. To date, no research on the metabolism of acacetin has been reported. In the current research, an online detection strategy of ultra-high-performance liquid chromatography connected to a quadrupole time-of-flight mass spectrometer (UHPLC-Q-TOF-MS/MS) was utilized for metabolite identification in vivo (rat plasma, bile, urine, and feces) and in vitro (rat liver microsomes). A total of 31 metabolites were structurally characterized in rats, and 25 metabolites were detected in rat liver microsomes, among which, 4 metabolites were compared with standards. Oxidation, the loss of CH2, reduction, hydrolysis, glucuronide conjugation, sulfate conjugation, methylation, and N-acetylation were the main metabolic pathways of acacetin. This study is the first to characterize acacetin metabolites in vivo and in vitro, and the results of this study offer novel and valuable evidence for a comprehensive understanding of the safety and efficacy of acacetin.

A Systematic Study of the Metabolites of Dietary Acacetin in Vivo and in Vitro Based on UHPLC-Q-TOF-MS/MS Analysis.

Acacetin, a natural dietary flavonoid abundantly found in acacia honey and citrus fruits, reportedly exerts several biological effects, such as anti-tumor, anti-inflammatory, and anti-oxidative effects. However, the effects of acacetin on intestinal inflammation remain unclear. We sought to investigate whether acacetin ameliorates inflammatory bowel disease (IBD) in mice with dextran sulfate sodium (DSS)-induced ulcerative colitis (UC). Our results suggest that acacetin alleviates the clinical symptoms of DSS-induced colitis, as determined by body weight loss, diarrhea, colon shortening, inflammatory infiltration, and histological injury. Further studies showed that acacetin remarkably inhibited both the macrophage inflammatory response in vitro and levels of inflammatory mediators in mice with colitis. In addition, some features of the gut microbiota were disordered in mice with DSS-induced colitis, as evidenced by a significant reduction in microbiota diversity and a marked shift in bacterial profiles. However, acacetin treatment improved this imbalance and restored gut microbiota to levels that were similar to those in normal mice. In conclusion, our work presents evidence that acacetin attenuates DSS-induced colitis in mice, at least in part, by inhibiting inflammation and regulating the intestinal microbiota.

/pdf/acacetin-ameliorates-experimental-colitis-in-mice-via-4ozmyjyfnh.pdf

Acacetin Ameliorates Experimental Colitis in Mice via Inhibiting Macrophage Inflammatory Response and Regulating the Composition of Gut Microbiota.

LC-MS-based untargeted metabolomics have been proven to be an extremely promising technique to discover biomarkers and explore the mechanisms underlying diseases, which, however, relies heavily on sample pretreatment for metabolite extraction. In the present study, a systematic and pragmatic evaluation of eight protocols employing conventional metabolites extraction strategies, protein precipitation (PPT), and liquid-liquid extraction (LLE), with and without proteinase K (PK) incubation, was performed simultaneously, using human plasma and a mixture of 39 endogenous metabolite standards. These protocols were as follows: (1) PPT with methanol, (2) PPT with acetonitrile, (3) PPT with 2-propanol, (4) two-step LLE of CH2Cl2-MeOH, followed by MeOH-H2O, (5) PK incubation combining two-step LLE of CH2Cl2-MeOH followed by MeOH-H2O, (6) two-step LLE of CHCl3-MeOH, followed by MeOH-H2O, (7) PK incubation combining two-step LLE of CHCl3-MeOH, followed by MeOH-H2O, (8) PK incubation combining MeOH-EtOH PPT. The results suggested that two-step LLE produced broader metabolome coverage than protein precipitation, and the addition of proteinase K enhanced the extraction performance further. Taken together, PK incubation combining two-step LLE of CHCl3-MeOH, followed by MeOH-H2O, was determined to be the most suitable extraction method, because of its broad metabolome coverage, high reproducibility, and satisfactory recovery. Next, the developed optimal sample preparation method was applied successfully to profile the plasma metabolome of colorectal adenoma and uncover its potential mechanism for significant differential changes in linoleic acid and phospholipid metabolism.

Proteinase K Combining Two-Step Liquid-Liquid Extraction for Plasma Untargeted Liquid Chromatography-Mass Spectrometry-Based Metabolomics To Discover the Potential Mechanism of Colorectal Adenoma.

Introduction: Polyphenols, which are widely distributed in plants and the human diets, are known to have numerous biological activities. However, the low bioavailability of polyphenols is mediated ...

An update on polyphenol disposition via coupled metabolic pathways.

Acacetin, an important component of acacia honey, exerts extensive therapeutic effects on many cancers. However, the sulfonation disposition of acacetin has rarely been reported. Therefore, this study aimed to investigate the sulfonation disposition of acacetin systematically. The results showed that acacetin-7-sulfate was the main metabolite mediated primarily by sulfotransferases (SULT) 1A1. Dog liver S9 presented the highest formation rate of acacetin-7-sulfate. Compared with that in wild-type Friend Virus B (FVB) mice, plasma exposure of acacetin-7-sulfate decreased significantly in multidrug resistance protein 1 knockout (Mrp1–/–) mice vut increased clearly in breast cancer resistance protein knockout (Bcrp–/–) mice. In Caco-2 monolayers, the efflux and clearance of acacetin-7-sulfate was reduced distinctly by the BCRP inhibitor Ko143 on the apical side and by the MRP1 inhibitor MK571 on the basolateral side. In conclusion, acacetin sulfonation was mediated mostly by SULT1A1. Acacetin-7-sulfate was f...

Zhong Qiu Liu

Papers

Sulfonation Disposition of Acacetin: In Vitro and in Vivo.