Structures of compounds 1–20 isolated from <i>P</i>. <i>tuberosa</i>.

<p>Asterisks indicate new compounds.</p

HPLC chromatogram of the ethyl acetate fraction of <i>P</i>. <i>tuberosa</i> extracts.

<p>Peaks with numbers represent isolated compounds.</p

¹H and ¹³C NMR data of compounds <b>1–4</b> in CD₃OD (400 MHz and 100 MHz for ¹H and ¹³C NMR, respectively; δ in ppm, <b><i>J</i></b> values in Hz).

<p>¹H and ¹³C NMR data of compounds <b>1–4</b> in CD₃OD (400 MHz and 100 MHz for ¹H and ¹³C NMR, respectively; δ in ppm, <b><i>J</i></b> values in Hz).</p

Origins and α-glucosidase inhibitory activities of the pure isolated compounds.

<p>Origins and α-glucosidase inhibitory activities of the pure isolated compounds.</p

Rapid Identification of α-Glucosidase Inhibitors from <i>Phlomis tuberosa</i> by Sepbox Chromatography and Thin-Layer Chromatography Bioautography

<div><p>Alpha-glucosidase inhibitors currently form an important basis for developing novel drugs for diabetes treatment. In our preliminary tests, the ethyl acetate fraction of <i>Phlomis tuberosa</i> extracts showed significant α-glucosidase inhibitory activity (IC₅₀ = 100 μg/mL). In the present study, a combined method using Sepbox chromatography and thin-layer chromatography (TLC) bioautography was developed to probe α-glucosidase inhibitors further. The ethyl acetate fraction of <i>P. tuberosa</i> extracts was separated into 150 individual subfractions within 20 h using Sepbox chromatography. Then, under the guidance of TLC bioautography, 20 compounds were successfully isolated from these fractions, including four new diterpenoids [14-hydroxyabieta-8,11,13-triene-11-carbaldehyde-18-oic-12-carboxy-13-(1-hydroxy-1-methylethyl)-lactone (<b>1</b>), 14-hydroxyabieta-8,11,13-triene-17-oic-12-carboxy-13-(1-hydroxy-1-methylethyl)-lactone (<b>2</b>), 14,16-dihydroxyabieta-8,11,13-triene-15,17-dioic acid (<b>3</b>), and phlomisol (15,16-eposy-8,13(16),14-labdatrien-19-ol) (<b>4</b>)], and 16 known compounds. Activity estimation indicated that 15 compounds showed more potent α-glucosidase inhibitory effects (with IC₅₀ values in the range 0.067–1.203 mM) than the positive control, acarbose (IC₅₀ = 3.72 ± 0.113 mM). This is the first report of separation of α-glucosidase inhibitors from <i>P. tuberosa</i>.</p></div