Mohammad Yasin Mohammad, Walid A. Al-Turk, M. Iqbal Choudhary and Atta-ur-Rahman
Faculty of Pharmacy, Middle East University, Amman-11831, Jordan; H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
Microorganisms have been used extensively for hydroxylation of terpenoidal compounds since their enzymes can catalyze reactions with high regio- and stereospecifity. Their ability to oxidize terpenoidal compounds has immense synthetic and commercial importance. Selected terpenoidal compounds (clerodane lactone (1), clerodane methyl ester (2), ferutinin (3) and thymoquinone (4)) were subjected to biotransformation using plant pathogen fungi Aspergillus niger, Fusarium lini and Rhizopus stolonifer. Clerodane lactone (C20H26O3) (1) and clerodane methyl ester (C21H30O4) (2) are diterpenoids isolated from Dodonaea viscose  and Pulicaria wightiana , respectively. Ferutinin (C22H30O4) (3), is a p-hydroxybenzoyl ester, is a potent naturally occurring non-steroid estrogenic compound that was isolated from the roots of Ferula harmonis , while thymoquinone (C10H12O2) (4), is a monoterpenoid isolated from the seeds of Nigella sativa. Incubation of clerodane lactone (1) with R. stolonifer yielded metabolites 5 and 6 (Fig. 1). While incubation of clerodane methyl ester (2) with R. stolonifer produced metabolites 7-10 (Fig. 2). Epoxidation of ferutinin (3) by A. niger, F. lini and R. stolonifer yielded metabolite 11 (Fig. 3) and transformation of thymoquinone (4) by A. niger produced compounds 12-14 (Fig. 4). Structures of compounds 5-14 were deduced through comparative spectroscopic studies with substrates 1-4. Compounds 5-11 showed moderate to good antibacterial activity against both Gram-positive and Gram-negative organisms, while metabolites 12-14 showed good antioxidant activity.
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Fig. 1:Transformation of clerodane lactone (1) by Rhizopus stolonifer.
Fig. 2:Transformation of clerodane methyl ester (2) by Rhizopus stolonifer.
Fig. 3:Biotransformation of ferutinin (3) by A. niger, F. lini, and R. stolonifer.
Fig. 4:Biotransformation of thymoquinone (4) by Aspergillus niger.