Inhibition of protein tyrosine phosphatase-1B (PTP1B) has been proposed as a therapy for treatment of type-2 diabetes and obesity. Bioassay-guided fractionation of an EtOAc-soluble extract of the root bark of Erythrina mildbraedii, using an in vitro PTP1B inhibitory assay, resulted in the isolation of three new isoprenylated flavonoids, abyssinone-IV-4'-O-methyl ether (2), 7-hydroxy-4'-methoxy-3'-(3-hydroxy-3-methyl-trans-but-1-enyl)-5'-(3-methylbut-2-enyl)flavanone (3), and abyssinone-VI-4-O-methyl ether (6), along with six known flavonoids, abyssinone-V-4'-O-methyl ether (1), abyssinone-V (4), abyssinone-IV (5), sigmoidin E (7), 4'-hydroxy-5,7-dimethoxyisoflavone (8), and alpinumisoflavone (9). Compounds 1 and 2, 4-7, and 9 inhibited PTP1B activity, with IC50 values ranging from 14.8 +/- 1.1 to 39.7 +/- 2.5 microM. On the basis of the data obtained, flavanones and chalcones with isoprenyl groups may be considered as a new class of PTP1B inhibitors.

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The extracts of some propolis samples were analysed by GC-MS and then purified by column chromatography. The latter led to the isolation of a new mono-ether of glycerol, 1'-O-eicosanyl glycerol and a new triterpene, methyl-3β,27-dihydroxycycloart-24-en-26-oate together with known triterpenoids namely betulin, 3β-hydroxylanostan-9,24-dien-21-oic acid, mangiferonic acid, a mixture of ambolic acid and β-sitosterol, 3β-hydroxycycloartan-12,24(25)-diene and 27-hydroxymangiferonic acid. The DPPH radical scavenging potential of some extracts and compounds were measured. The radical scavenging activity varied from Hexane extract of Foumban propolis (IC = 5.6 mg/mL) to Methanol extract of Foumban propolis (IC = 1.07 mg/mL) for the extracts and from 3β-hydroxylanostan-9,24-dien-21-oic acid (IC = 1.22 mg/mL) to 1'-O-eicosanyl glycerol (IC = 0.93 mg/mL) for the compounds. Activities of samples were moderate as they remained closer to those of the standard antioxidants Gallic acid (IC = 0.30 mg/mL) and vitamin C (IC = 0.80 mg/mL), especially 1'-O-eicosanyl glycerol, the most active compound.

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Phytochemical study on an EtOAc-soluble extract of the root bark of Erythrina mildbraedii resulted in the isolation of six prenylated flavonoids 1-6. Based on physicochemical and spectroscopic analyses, their structures were determined to be new natural products licoflavanone-4-O-methyl ether (1), 2,7-dihydroxy-4-methoxy-5-(3-methylbut-2-enyl)isoflavone (2), and (3R)-2,7-dihydroxy-3-(3-methylbut-2-enyl)