Microbial Transformations of Natural Antitumor Agents: Products of Rotenone and Dihydrorotenone Transformation by Cunninghamella blakesleeana

Abstract

Various species of Absidia, Aspergillus, Cunninghamella, Trichothecium, Penicillium, and Phanerochaete were found to transform rotenone to one or more metabolites. Two biotransformation products were isolated from a preparativescale incubation of rotenone with Cunninghamella blakesleeana and identified as 1',2'-dihydro-1',2'-dihydroxyrotenone and 3'-hydroxyrotenone (amorphigenin). The catalytic reduction of the isopropylene side chain of rotenone resulted in the formation of 1',2'-dihydrorotenone. The latter was transformed by C. blakesleeana to 2'-hydroxy-1',2'-dihydrorotenone. Rotenoids are components of the roots, stems, and leaves of many leguminous species of the genera Derris, Lonchocarpus, Tephrosia, and Amorpha. Rotenone, a prominent component of this group, was first isolated in 1895 (12), but its structure was established only recently (2, 6, 7, 10). It is a well-characterized inhibitor of the mitochondrial respiratory chain at the level of NADH dehydrogenase (3). Rotenoids have been widely used as nonpersistent pesticides because of their effectiveness, selectivity, and apparently low environmental hazard. Although the metabolism of rotenone has been studied in mammals and insects (11, 13), no studies on the microbial metabolism or transformation of this compound have been reported. Aspects of the chemistry, biochemistry, metabolism, pharmacology, and toxicology of rotenone have been reviewed (13), and the need for further studies on the metabolism of this compound, including definitive identification of metabolites formed by various species, has been emphasized (13). This report identifies the products of rotenone and of 1',2'-dihydrorotenone when metabolized by Cunninghamella blakesleeana. MATERIALS AND METHODS Organisms and fermentation procedures. The cultures used in this study are maintained in the University of Iowa College of Pharmacy culture collection and are stored in sealed screw-capped tubes at 4°C. Organisms were grown in a medium of the following composition: soybean meal (5 g), glucose (20 g), yeast extract (5 g), NaCl (5 g), K2HPO4 (5 g), and distilled water (1.0 liter), adjusted to pH 7.0 with 5 N HCI. The media were sterilized in an autoclave at 121°C for 15 min.

Biotransformations of 1',2'-dihydrorotenone by Streptomyces griseus

“…Accompanying deshielding of carbons 2, 1', 3', 6, 6b, 12a, and 12 and the expected changes in the proton NMR spectrum confirm the structure of the metabolite as compound 3. This compound is identical to one of the biotransformation products of compound 1 formed by C. blakesleeana and previously identified in our laboratory (6).…”

“…Proton NMR spectral findings were also consistent for the structure of the fermentation product as compound 2. The 1H NMR spectrum was similar to that of compound 1, except for the position 7 aromatic proton signal, which serves as an indicator for the presence of a P-hydroxyl group at position 6a (6).…”

“…Rotenoids are widely used as natural pesticides, and they are subject to microbial (6), enzymatic (Sa), and photochemical oxidations (2). In a previous report (6), metabolites of rotenone and 1',2'-dihydrorotenone formed by cultures of the fungus Cunninghamella blakesleeana were isolated and identified. This organism introduced hydroxyl groups into the isopropylene and isopropyl moieties of the two substrates.…”

Natural Pesticide Dihydrorotenone Arrests Human Plasma Cancer Cells at the G0/G1 Phase of the Cell Cycle

“…Rotenone is the major natural pesticidal component of derris and Lonchocarpus of the Fabaceae family and has been used for fishing, farming, and gardening. Dihydrorotenone (DHR) is a reduction product of rotenone catalyzed by soil bacteria that saturate the dual bond of the side chain of rotenone . Both rotenone and DHR are natural pesticides that are commonly marketed and sold under the rubric “organic gardening supplies” .…”

Toxicity of Amorphigenin from the Seeds of Amorpha fruticosa against the Larvae of Culex pipiens pallens (Diptera: Culicidae)

“…According to the similarity of spectral data to that reported by Sariaslani et al . [ 51 ] and Abe et al . [ 52 ], the abovementioned data, suggest that the obtained compound was identical to the known rotenoid, amorphigenin ( Figure 4 ).…”