Biotransformation of Ilicic Alcohol with Aspergillus Niger

Abstract

3β-hidroxyilicic alcohol was obtained from of ilicic alcohol using cultures of Aspergillus niger.

Introduction

Sesquiterpenes are wide spread Asteracea Compositae family. Their derivatives present several biological activities. Among them we have studied their gastrointestinal citoprotective action and the antinflamatory effects. The production of active metabolites by transformation of low funcionalized natural products is an attractive idea. In previous reports we have described the hydroxylation of the eudesmane, ilicic acid, in positions 1β y 2β [1] and the production of trihydroxyderivatives in posi- tions 2β y 3α from kudtdiol [2] by Cunningamella echinulata.

Materials and methods

Culture Conditions: Modified Czapek broth [3] was used to carry out the biotransformation reac- tions. Agar Czapek was employed to maintain the strains. Taking into account a previous screening, we have chosen an Aspergillus niger strain, isolated from aerial parts of Artemisia donglassiana. Bio- transformations were performed according to a two steps fermentation process.

Biotransformation products were recover from the culture media by liquid-liquid extraction with Et2O and purified by CC with a gradient of n-hexane/AcEt. 80mg of the biotransformation product were obtained. The hydroxylation position was defined by NMR and MS analysis.

Results and Discusion

The comparison of the 1H NMR spectrums in CCl3D of the new product versus the ones of the sub- strate suggested us that the hydroxylation position was 3β. The sing at δ 3.43 ppm was attributable to a geminal hydrogen in α-equatorial conformation. This proposal was confirmed through the coupling pattern (J=11.5 y 4.5 Hz). 1H-NMR shifts are in accordance with the ones recently reported for 3β- hydroxylicic acid isolated from other sources [4]. The impossibility to obtain the acetonic derivative

confirm that the hydroxylic group was introduced in position in C-3, trans respect to the hydroxylixc group in C-4.

It was recently reported that Cunninghamella echinulata NRRL 3655 hydroxylated both, ilicic acid and kudtdiol in positions C-1β, C-2β y C-3α. These results, together with the ones reported here, shown us the ability of these microorganisms to hydroxylate in positions cis respect to the methyl grops in C-4 y C-10