Salazinic Acid-Derived Depsidones and Diphenylethers with α-Glucosidase Inhibitory Activity from the Lichen Parmotrema dilatatum

Abstract

Three new depsidones, parmosidones F – G (1 – 2), and 8′-O-methylsalazinic acid (3), and 3 new diphenylethers, parmetherines A – C (4 – 6), together with 2 known congeners were isolated from the whole thalli of Parmotrema dilatatum, a foliose chlorolichen. Their structures were unambiguously determined by extensive spectroscopic analyses and comparison with literature data. The isolated polyphenolics were assayed for their α-glucosidase inhibitory activities. Newly reported benzylated depsidones 1 and 2 in particular inhibited α-glucosidase with IC50 values of 2.2 and 4.3 µM, respectively, and are thus more potent than the positive control, acarbose.

Alpha-glucosidase inhibitors from Nervilia concolor, Tecoma stans, and Bouea macrophylla

“…Saccharomyces cerevisiae α-glucosidase (E.C 3.2.1.20), acarbose, and 4-nitrophenyl β-D-glucopyranoside (pNPG) were obtained from Sigma-Aldrich Co (Saint Louis, MI, USA). The alpha-glucosidase (0.2 U/mL) and substrate (5.0 mM p-nitrophenyl-β -D-glucopyranoside) were dissolved in 100 mM of pH 6.9 sodium phosphate buffer ( Devi et al, 2020 ). The inhibitor (50 µL ) was preincubated with alpha-glucosidase at 37 °C for 20 min, then 40 µL of substrate was added to the reaction mixture.…”

“…The enzymatic reaction was carried out at 37 °C for 20 min and stopped by adding 0.2 M Na 2 CO 3 (130 μL). The method followed that in a previous report ( Devi et al, 2020 ).…”

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

“…The alpha-glucosidase (0.2 U/mL) and substrate (5.0 mM p -nitrophenyl-α-D-glucopyranoside) were dissolveed in 100 mM of pH 6.9 sodium phosphate buffer [ 27 ]. The inhibitor (50 µL) was preincubated with alpha-glucosidase at 37 °C for 20 min, and then the substrate (40 µL) was added to the reaction mixture.…”

Alpha-Glucosidase Inhibitory Diterpenes from Euphorbia antiquorum Growing in Vietnam

“…Saccharomyces cerevisiae α-glucosidase (E.C 3.2.1.20), acarbose, and 4-nitrophenyl β-Dglucopyranoside (pNPG) were obtained from Sigma-Aldrich Co (Saint Louis, MI, USA). The alpha-glucosidase (0.2 U/mL) and substrate (5.0 mM pNPG) were dissolved in 100 mM pH 6.9 sodium phosphate buffer [17]. The inhibitor (50 µL) was preincubated with alphaglucosidase at 37 • C for 20 min, and then the substrate (40 µL) was added to the reaction mixture.…”