Flavones from Combretum quadrangulare Growing in Vietnam and Their Alpha-Glucosidase Inhibitory Activity

Abstract

Combretum quadrangulare Kurz is widely used in folk medicine in Eastern Asia and is associated with various ethnopharmacological properties including hepatoprotective, antipyretic, analgesic, antidysenteric, and anthelmintic activities. Previous phytochemical investigations reported the presence of numerous triterpenes (mostly cycloartanes, ursanes, lupanes, and oleananes) along with dozens of flavonoids. However, the extracts of C. quadrangulare and isolated flavonoids have not been evaluated for their alpha-glucosidase inhibition. In the frame of our efforts dedicated to the chemical investigation of Vietnamese medicinal plants and their biological activities, a phytochemical study of the MeOH extract of the leaves of C. quadrangulare using bioactive guided isolation was undertaken. In this paper, the isolation and structure elucidation of twelve known compounds, 5-hydroxy-3,7,4′-trimethoxyflavone (1), ayanin (2), kumatakenin (3), rhamnocitrin (4), ombuin (5), myricetin-3,7,3′,5′-tetramethyl ether (6), gardenin D (7), luteolin (12), apigenin (13), mearnsetin (14), isoorientin (15), and vitexin (16) were reported. Bromination was applied to compounds 2 and 3 to provide four new synthetic analogues 8–11. All isolated and synthesized compounds were evaluated for alpha-glucosidase inhibition and antibacterial activity. Compounds 4 and 5 showed moderate antibacterial activity against methicillin-resistant Staphylococcus aureus while others were inactive. All compounds failed to reveal any activity toward extended spectrum beta-lactamase-producing Escherichia coli. Compounds 2, 4, 6–9, and 11–14 showed good alpha-glucosidase inhibition with IC50 values in the range of 30.5–282.0 µM. The kinetic of enzyme inhibition showed that 8 and 11 were noncompetitive type inhibition against alpha-glucosidase. In silico molecular docking model indicated that compounds 8 and 11 were potential inhibitors against enzyme α-glucosidase.

Ombuin ameliorates diabetic nephropathy in rats by anti‐inflammation and antifibrosis involving Notch 1 and PPAR γ signaling pathways

“…Ombuin exists in a variety of plants, many of which are used as traditional medicines to treat a variety of human diseases (Dao et al, 2021; Nguyen et al, 2021; Park et al, 1998). At present, the biological activities of ombuin in antibacteria (Dao et al, 2021), anti‐inflammation (Rao et al, 2010), anti‐oxidation (Ranjana et al, 2019), and anticancers (Park et al, 1998) have been reported in previous studies. In a recent study, it was also confirmed that ombuin has the potential to improve type 2 diabetes (Kikiowo et al, 2020).…”

“…Ombuin (C 17 H 14 O 7 ) is a natural flavonoid compound that exists in a variety of natural plants and has been proven to have antibacterial (Dao et al, 2021), antioxidant (Ranjana et al, 2019), anticancer (Park et al, 1998), and other biological activities. Rao et al (2010) found that ombuin can significantly and dose-dependently inhibit the release of nitric oxide and cytokines induced by lipopolysaccharide or interferon-γ, and is a potential new anti-inflammatory drug.…”

New Derivatives of Lupeol and Their Biological Activity

“…The α-glucosidase (0.2 U/mL) and substrate (5.0 mM p-nitrophenyl-α-D-glucopyranoside) were dissolved in 100 mM pH 6.9 sodium phosphate buffer [12]. The inhibitor (50 µL) was preincubated with α-glucosidase; then, the substrate (40 µL) was added to the reaction mixture.…”

Evaluation of the Acute and Sub-Acute Oral Toxicity of Jaranol in Kunming Mice

“…, Psychotria serpens and Siparuna cristata ( Chen 2011 ; Xue et al, 2013 ). Some studies illustrated that jaranol had a potential role in inhibiting SARS-CoV-2 replication ( Leal et al, 2021 ) and exerting anti-cancer ( Woo et al, 2017 ), alpha-glucosidase inhibitory ( Dao et al, 2021 ), anti-bacterial ( Zhang et al, 2019 ), and anti-oxidant activities in vitro ( Quek et al 2021 ). At present, no studies evaluating the effect of jaranol in vivo were found from a PubMed search with the keywords jaranol or kumatakenin.…”