Abstract
The tube assay methods of lipoic acid with Streptococcus faecalis R by Yamasaki et al. and with Corynebacterium bovis 187 by Stokstad were applied to the bioassay of lipoic acid in human urine. The data of same urine samples obtained by the two methods were almost equal, but the recovery of added DL-lipoic acid was not satisfactory in the method with C. bovis, though that of the method with Stc. faecalis R was enough. It is supposed that the growth response of C. bovis for lipoic acid in urine might be inhibited by some substances in urine. The biological activities of some lipoic conjugates for the both microbes were compared. N-DL-lipoyl-DL-glutamate was found to be fully active for the growth of C. bovis, while almost inactive for that of Stc. faecalis.
