1. Introduction
Biotransformation is an important tool for the synthesis of
medicinally important organic compounds. The use of biocatalysis
for the stereoselective synthesis of chiral molecules has several
advantages over classical chemical synthesis. Biocatalyzed reactions
are generally regio- and stereo-selective, cost effective and
environmental friendly [1–6]. Microbial cultures are frequently
used for biocatalysis. Microorganisms contain a large variety of
enzymes which catalyze many chemical reactions, including oxidation,
hydroxylation, and reduction. Fungi can also serve as
microbial models of mammalian steroid drug metabolism.
Microbial cytochrome P450 monooxygenase system facilitates
stereoselective hydroxylation at multiple sites of steroidal skeleton.
Stereoselective hydroxylation of steroids at non activated
position have been achieved by using various fungi [7–9].
Danazol (1) is a heterocyclic steroidal drug in which an isoxazole
ring is fused with ring-A of a steroidal nucleus. It is a synthetic
analogue of 17a-ethinyltestosterone. Danazol (1) inhibits endometrial
tumor cell migration and invasive activity [10]. Compound 1 is
orally effective, and used for the treatment of endometriosis, and
for the inhibition of pituitary gonadotropin. It is also used in the
treatment of precocious puberty, and benign fibrocystic mastitis
[11–14].
Cancer is a major cause of human mortality. Many current
chemotherapic agents against cancers, such as doxorubicin, function
by highly toxic, untargeted DNA damage mechanisms. Their
efficacy is now seriously challenged by emerging multidrugresistant
in cancer cells [15–17]. However, hormonal therapies
targeting cancer do not rely on DNA damage. The HeLa cell line
is derived from a human cervical cancer and is a common model
to study preliminary anti-cancer potential of chemical compounds
[18]. Initially, we evaluated danazol (1) against the HeLa cell line,
where it showed an excellent cytotoxic effect. Therefore, we
decided to evaluate the transformed products of 1 against this cell
line. Interestingly, only compound 3 showed some level of
cytotoxicity against HeLa cell line.
This manuscript is in the continuation of our studies on the
biotransformation of bioactive steroidal compounds [19–23]. We
subjected danazol (1) to biotransformation with C. blakesleeana,
which yielded three new metabolites 2–4, and a known metabolite