For determination of 5-reductase inhibitory activity, radioimmunoassay
(RIA) is the most widely accepted method. However
RIA, which uses a radioactive compound, requires many complexes
instruments and other equipment. Although immunoassay is a
fast and easy method, there is a cross-reactivity of many androgens
(Lootens et al., 2008). Matsuda et al. (2001) developed a
simple isocratic HPLC method. In our previous paper, we modified
the detection wavelength from 254 nm to 245 nm which
encounters less interference from the reaction system (Kumar
et al., 2011). In this experiment, finasteride has IC50 at 0.39 M