Α-glucosidase inhibitor isolated from coffee.

The potent α-glucosidase inhibitor (compound I) was isolated from coffee brews by the activity-based fractionation and identified as a ß-carboline alkaloid norharman (9H-pyrido[ 3.4-b]indole) on the basis of mass spectroscopy and nuclear magnetic resonance spectra ((1)H NMR, (13)C NMR, and COSY). The norharman showed a potent inhibition against α-glucosidase enzyme in a concentration dependent manner with an IC50 value of 0.27 mM for maltase and 0.41 mM for sucrase, respectively. A Lineweaver-Burk plot revealed that norharman inhibited α-glucosidase enzyme uncompetitively, with a Ki value of 0.13 mM.

Characterization of an antibiotic produced by Bacillus subtilis JW-1 that suppresses Ralstonia solanacearum.

Bacillus subtilis JW-1 was isolated from rhizosphere soil as a potential biocontrol agent of bacterial wilt caused by Ralstonia solanacearum. Seed treatment followed by a soil drench application with this strain resulted in >80% reduction in bacterial wilt disease compared with that in the untreated control under greenhouse conditions. The antibacterial compound produced by strain JW-1 was purified by bioactivity-guided fractionation. Based on mass spectroscopy and nuclear magnetic resonance spectral data ((1)H, (13)C, (1)H-(1)H correlation spectroscopies, rotating frame nuclear Overhauser effect spectroscopy, and heteronuclear multiple-bond correlation spectroscopy), the structure of this compound was elucidated as a cyclic lipopeptide composed of a heptapeptide (Gln-Leu-Leu-Val-Asp-Leu-Leu) bonded to a ß-hydroxy-iso-hexadecanoic acid arranged in a lactone ring system.

α-Glucosidase inhibitor from Buthus martensi Karsch.

A bioassay-guided fractionation of an ethanol extract of Buthus martensi Karsch led to the isolation of a potent α-glucosidase inhibitor (compound S). The structure was elucidated as a novel ß-carboline glucoalkaloid, harmanyl ß-d-glucopyranoside, on the basis of spectral data, including (1)H NMR, (13)C NMR, (1)H-(1)H COSY, NOESY, and HMBC. Compound S showed potent inhibitory activity against α-glucosidase, with an IC(50) value of 24 µM. A Lineweaver-Burk plot indicated that its inhibition of α-glucosidase was uncompetitive, with a Ki value of 16.1 µM.

Isolation and structure determination of a cholesterol esterase inhibitor from Ganoderma lucidum.

Bioassay-guided fractionation of methanol extract of Ganoderma lucidum gave a pure cholesterol esterase inhibitor. On the basis of spectroscopic analysis and comparison with data from the literature, its structure was identified as 5alpha,8alpha-epidioxyergosta-6,22-dien-3beta-ol (compound I). Compound (I) inhibited cholesterol esterase with an IC50 value of 42 micronM. A Lineweaver-Burk plot revealed that the compound (I) is a noncompetitive inhibitor. Findings from this study suggest that compound (I) may be the active principle of the hypocholesterolemic effect of Ganoderma lucidum.

Isolation and characterization of alpha-glucosidase inhibitor from the fungus Ganoderma lucidum.

An alpha-glucosidase inhibitor, SKG-3, was isolated from the fruiting bodies of Ganoderma lucidum and its physico-chemical properties were characterized. It was a highly specific and effective reversible inhibitor of alpha-glucosidase. It showed very potent inhibitory activity against alpha-glucosidase with an IC50 value of 4.6 micro g/ml, but no activity for any other glycosidases tested. Enzyme activity could be recovered upon dialysis, thus providing evidence for the reversibility of the inhibition. A Lineweaver-Burk plot indicated that the SKG-3 inhibition of alpha-glucosidase was competitive.