title: Chemical Constituents of Malaysian U. cordata var. ferruginea and Their in Vitro α-Glucosidase Inhibitory Activities.
abstract: Continuing our interest in the Uncaria genus, the phytochemistry and the in-vitro α-glucosidase inhibitory activities of Malaysian Uncaria cordata var. ferruginea were investigated. The phytochemical study of this plant, which employed various chromatographic techniques including recycling preparative HPLC, led to the isolation of ten compounds with diverse structures comprising three phenolic acids, two coumarins, three flavonoids, a terpene and an iridoid glycoside. These constituents were identified as 2-hydroxybenzoic acid or salicylic acid (1), 2,4-dihydroxybenzoic acid (2), 3,4-dihydroxybenzoic acid (3), scopoletin or 7-hydroxy-6-methoxy-coumarin (4), 3,4-dihydroxy-7-methoxycoumarin (5), quercetin (6), kaempferol (7), taxifolin (8), loganin (9) and β-sitosterol (10). Structure elucidation of the compounds was accomplished with the aid of 1D and 2D Nuclear Magnetic Resonance (NMR) spectral data and Ultraviolet-Visible (UV-Vis), Fourier Transform Infrared (FTIR) spectroscopy and mass spectrometry (MS). In the α-glucosidase inhibitory assay, the crude methanolic extract of the stems of the plant and its acetone fraction exhibited strong α-glucosidase inhibition activity of 87.7% and 89.2%, respectively, while its DCM fraction exhibited only moderate inhibition (75.3%) at a concentration of 1 mg/mL. The IC50 values of both fractions were found to be significantly lower than the standard acarbose suggesting the presence of potential α-glucosidase inhibitors. Selected compounds isolated from the active fractions were then subjected to α-glucosidase assay in which 2,4-dihydroxybenzoic acid and quercetin showed strong inhibitory effects against the enzyme with IC50 values of 549 and 556 μg/mL compared to acarbose (IC50 580 μg/mL) while loganin and scopoletin only showed weak α-glucosidase inhibition of 44.9% and 34.5%, respectively. This is the first report of the isolation of 2-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid and loganin from the genus and the first report of the α-glucosidase inhibitory potential of 2,4-dihydroxybenzoic acid.
authors.affiliation: Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor Darul Ehsan, Malaysia. kimsyaz@yahoo.com.
authors.forename: Nur Hakimah
authors.initials: NH
authors.lastname: Abdullah
authors.affiliation: Center of Foundation Studies, Universiti Teknologi MARA, Dengkil Campus, 43800 Dengkil, Selangor Darul Ehsan, Malaysia. fatimahsalim10@gmail.com.|Atta-ur-Rahman Institute for Natural Products Discovery, Universiti Teknologi MARA, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia. fatimahsalim10@gmail.com.
authors.forename: Fatimah
authors.initials: F
authors.lastname: Salim
authors.affiliation: Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor Darul Ehsan, Malaysia. rohayaahmad@salam.uitm.edu.my.|Atta-ur-Rahman Institute for Natural Products Discovery, Universiti Teknologi MARA, 42300 Bandar Puncak Alam, Selangor Darul Ehsan, Malaysia. rohayaahmad@salam.uitm.edu.my.
authors.forename: Rohaya
authors.initials: R
authors.lastname: Ahmad
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003374:Coumarins / Q000737:chemistry / Q000494:pharmacology; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology; D065089:Glycoside Hydrolase Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D062385:Hydroxybenzoates / Q000737:chemistry / Q000494:pharmacology; D066298:In Vitro Techniques; D057889:Iridoid Glycosides / Q000737:chemistry / Q000494:pharmacology; D015394:Molecular Structure; D010936:Plant Extracts / Q000032:analysis* / Q000737:chemistry / Q000494:pharmacology; D013729:Terpenes / Q000737:chemistry / Q000494:pharmacology; D032070:Uncaria / Q000737:chemistry*
chemical_list: D003374:Coumarins; D005419:Flavonoids; D065089:Glycoside Hydrolase Inhibitors; D062385:Hydroxybenzoates; D057889:Iridoid Glycosides; D010936:Plant Extracts; D013729:Terpenes; C017616:phenolic acid
keywords: 2,4-dihydroxybenzoic acid; 2-hydroxybenzoic acid; Uncaria cordata; loganin; phytochemistry; α-glucosidase inhibition