Characterization of active compounds from Gracilaria lemaneiformis inhibiting the protein tyrosine phosphatase 1B activity.

Gracilaria lemaneiformis, an edible alga, with various bioactivities is a traditional dish and a favorite food. In the present study, its n-hexane extract showed strong protein tyrosine phosphatase 1B inhibitory activity after screening. To understand the activity composition, nineteen compounds were identified from this extract by GC-MS. The protein tyrosine phosphatase 1B inhibitory activity of the identified compounds was further screened by means of molecular docking individually. As a result, 2,2'-methylenebis-6-(1,1-dimethylethyl)-4-methyl-phenol with the lowest binding energy of -6.70 kcal mol-1 was discovered from the complex extract, and its inhibitory activity against protein tyrosine phosphatase 1B was proved in vitro. The IC50 value was 53.27 ± 0.54 µM. Therefore, this compound and its source Gracilaria lemaneiformis were suggested to be utilized as a functional food with potential protein tyrosine phosphatase 1B inhibitory activity.

Rapid prediction and identification of lipase inhibitors in volatile oil from Pinus massoniana L. needles.

A facile method based on gas chromatography-mass spectrometry (GC-MS) and molecular docking was established to analyze, identify, and predict lipase inhibitors in volatile oil from Pinus massoniana L. needles (PMLN). The volatile oil, with an IC50 value of 15.25 ± 0.06 µg/mL, exhibited potential inhibitory activity against lipase in vitro. In total, 33 compounds were identified from the volatile oil through GC-MS analysis. The major compounds in the volatile oil were ß-pinene (39.24%), α-pinene (14.68%), germacrene D (9.08%), caryophyllene (6.94%), α-terpineol (5.39%), ß-phellandrene (4.82%), and D-limonene (3.93%). The identified compounds were individually docked with lipase as the target through molecular docking. Among the compounds, longifolene characterized by preferable binding energy and the good inhibition constant exhibited potential lipase inhibitory activity. The IC50 value of longifolene was 25.10 ± 0.49 µM, indicating that this compound is the active ingredient responsible for the lipase inhibitory activity of PMLN volatile oil.

Rational approach to solvent system selection for liquid-liquid extraction-assisted sample pretreatment in counter-current chromatography.

A rational liquid-liquid extraction approach was established to pre-treat samples for high-speed counter-current chromatography (HSCCC). n-Hexane-ethyl acetate-methanol-water (4:5:4:5, v/v) and (1:5:1:5, v/v) were selected as solvent systems for liquid-liquid extraction by systematically screening K of target compounds to remove low- and high-polarity impurities in the sample, respectively. After liquid-liquid extraction was performed, 1.4g of crude sample II was obtained from 18.5g of crude sample I which was extracted from the flowers of Robinia pseudoacacia L., and then separated with HSCCC by using a solvent system composed of n-hexane-ethyl acetate-methanol-water (1:2:1:2, v/v). As a result, 31mg of robinin and 37mg of kaempferol 7-O-α-l-rhamnopyranoside were isolated from 200mg of crude sample II in a single run of HSCCC. A scale-up separation was also performed, and 160mg of robinin with 95% purity and 188mg of kaempferol 7-O-α-l-rhamnopyranoside with 97% purity were produced from 1.2g of crude sample II.

Bioassay-guided isolation of an active compound with protein tyrosine phosphatase 1B inhibitory activity from Sargassum fusiforme by high-speed counter-current chromatography.

A rapid and efficient method using high-speed counter-current chromatography was established for the bioassay-guided separation of an active compound with protein tyrosine phosphatase 1B inhibitory activity from Sargassum fusiforme. Under the bioassay guidance, the ethyl acetate extract with the best IC50 value of 0.37 ± 0.07 µg/mL exhibited a potential protein tyrosine phosphatase 1B inhibitory activity, which was further separated by high-speed counter-current chromatography. The separation was performed with a two-phase solvent system composed of n-hexane/methanol/water (5:4:1, v/v). As a result, dibutyl phthalate (19.7 mg) with the purity of 95.3% was obtained from 200 mg of the ethyl acetate extract. Its IC50 was 14.05 ± 0.06 µM, which was further explained by molecular docking. The result of molecular docking showed that dibutyl phthalate enfolded in the catalytic site of protein tyrosine phosphatase 1B. The main force between dibutyl phthalate and protein tyrosine phosphatase 1B was the hydrogen bond interaction with Gln266. In addition, hydrogen bond, van der Waals force and hydrophobic interaction with the amino acids (Ala217, Ile219, and Gly220) were also responsible for the stable protein-ligand complex.