Records of Natural Products

Phytochemical investigation of Psammosilene tunicoides led to isolation of a new cyclic peptide, psammosilenin C (1) and three known compounds, 1-O-(β-D-glucopyranosyl)-(2S,3R,4E,8E)-2-[(2R)-2-hydroxypentadecanoylamino]-4,8-octadecadiene-1,3-diol (2), dihydroferulic acid (3) and vanillylacetone (4). Their structures were elucidated by comprehensive spectroscopic methods, including 1D and 2D NMR spectroscopic, and HR-ESI-MS spectrometric data. Compounds 1, 2 and 4 showed inhibitory activities on lipopolysaccharide (LPS)-induced NO release in RAW 264.7 cells.

Type 2 diabetes mellitus is a disease caused by insulin resistance. Many types of oral medications exist, but the effectiveness and side effects differ from patient to patient, so alternative drugs are still required. One compound group receiving much scientific interest regarding its antidiabetic potential is xanthones as potential alpha-glucosidase and alpha-amylase inhibitors. This study performed molecular docking simulations on all 515 natural xanthones with alpha-glucosidase and alpha-amylase as the protein targets. We found 31 unique ligands that comply, and the three best ligands per protein target were filtered based on how many active site residues the ligands interacted with the targets. The three best alpha-glucosidase inhibitors are 3,4,5,8-tetrahydroxy-1,2-diisoprenylxanthone, Polygalaxanthone V, and Polygalaxanthone VII. As for alpha-amylase, we found 1-O-primeverosyl-3,8-dihydroxy-5-methoxyxanthone, Garcimangosone C, and Mangostinone as the best inhibitors. The six chosen and standard ligands underwent 2 ns molecular dynamics simulations. Both standard ligands had the highest interaction energies, followed by complexes with glycosylated xanthones, and prenylated xanthones. We also found that the prenylated xanthones could retain their initial protein-ligand interactions. Therefore, this is the first study that revealed prenylated xanthones have a good potential as anti-type 2 diabetes mellitus agents among other xanthones groups through in silico method.

The genus Teucrium L., belonging to the family Lamiaceae, is divided in ten sections including Polium (Mill.) Schreb. In Cyprus, this section is represented by five endemic species: T. micropodioides, T. cyprium, T. karpasiticum, T. kyreniae and T. salaminium. Essential oils of the aerial parts of these species were separately obtained by hydrodistillation using a Clevenger-type apparatus. Chemical compositions of the obtained oils were analyzed by GC and GC/MS, simultaneously. The essential oil yields ranged between 0.03-0.75 (v/w). The major components of the essential oil of T. kyreniae were β-caryophyllene (21.2%), (Ε)-nerolidol (10.9%), carvone (8.8%) and α-humulene (7.9%). T. salaminium essential oil was dominated by β-caryophyllene (15.2%), caryophyllene oxide (13.9%), germacrene D (11.6%) and bicyclogermacrene (10.0%). Major components of the oil of T. cyprium were β-pinene (35.4%), α-pinene (10.6%) and spathulenol (8.4%). Major compounds of the oils of T. micropodioides samples, collected from two different locations, were (1) limonene (47.0%), β-pinene (16.0%) and β-caryophyllene (6.9%), (2) δ-cadinene (11.2%), 1-epi-cubenol (7.8%), cubebol (4.7%), cubenol (4.1%), respectively. Main constituents of the essential oil of T. karpasiticum were limonene (43.9%), β-pinene (16.0%), α-bisabolol oxide A (7.8%), β-caryophyllene (5.5%) and α-pinene (4.6%). The section Polium, is considered a complex and the diversity of oil compositions from the species belonging to this section provided additional proof to this consideration.

An updated phytochemical investigation of the aerial parts of Amomum muricarpum Elmer led to the isolation of a new megastigmane glycoside, (3S*,5R*,6R*,9R*)-6,9-epoxy-3,5-megastigmanediol 3-O-rutinoside (1) and five known phenolic compounds. Their structures were elucidated by spectroscopic evidence including HRESIMS and NMR data. All the isolates were reported for the first time from this plant. The anti-inflammatory effect via the inhibition of NO production of isolated compounds was evaluated in LPS-stimulated RAW 264.7 cells. Our study found that 5,7-dimethoxyflavone (4) was the most active compound with the IC50 = 29.5 µM.