Noriko Tabata

Xanthohumols, diacylglycerol acyltransferase inhibitors, from Humulus lupulus.

A methanol extract of hops of Humulus lupulus (L.) showed inhibitory activity against rat liver diacylglycerol acyltransferase (DGAT). From DGAT inhibitory activity-guided fractionation, two chalcones were isolated. One was identified as xanthohumol and the other was found to be a new product designated xanthohumol B. The structure of xanthohumol B was shown to be 6-[3,4-dihydro-3,5-dihydroxy-7-methoxy-2,2-dimethyl-2H-benzo[b]pyrano ]- 3-(4-hydroxyphynyl)-2-propen-l-one by spectroscopic studies including various NMR measurements. Xanthohumol and xanthohumol B inhibited DGAT activity with IC50 values of 50.3 and 194 microM in rat liver microsomes, respectively. They showed preferential inhibition of triacylglycerol formation in intact Raji cells, indicating that they inhibit DGAT activity preferentially in living cells.

Pyripyropenes, novel ACAT inhibitors produced by Aspergillus fumigatus. III: Structure elucidation of pyripyropenes E to L

Eight new pyripyropenes, E to L, were isolated from the culture broth of Aspergillus fumigatus FO-1289-2501 selected as a higher producer by NTG mutation. Structural elucidation indicated that all the pyripyropenes have the same pyridino-alpha-pyrone sesquiterpene core as pyripyropenes A to D. Among them, pyripyropene L showed the most potent inhibition against acyl-CoA: cholesterol acyltransferase (ACAT) activity with an IC50 value of 0.27 microM in rat liver microsomes.

The structure of xanthoquinodin A1, a novel anticoccidial antibiotic having a new xanthone-anthraquinone conjugate system

The structure of the anticoccidial antibiotic xanthoquinodin A1(1), isolated from Humicola sp. FO-888, was elucidated by 1H- and 13C-NMR experiments. It contains a new type of xanthone and anthraquinone conjugate system.

Asymmetric synthesis of the anticoccidial antibiotic diolmycin A1. Determination of absolute stereochemistry

Abstract An asymmetric total synthesis of diolmycin A1 (1), a recently discovered anticoccidial antibiotic, has been achieved in six steps from 2-(4-hydroxyphenyl)ethanol. The natural product comprises an unusual ca. 4:1 mixture of enantiomers; the synthesis defined the (11R,12S) absolute configuration of the predominant (−) antipode.