Constituents of human meconium--III. Identification of 3,20-dihydroxypregnan-21-oic acids.

Seven 3,20-dihydroxypregnan-21-oic acids (C21) were detected by capillary gas chromatography-mass spectrometry in the acid fraction isolated from human meconium after solvolysis and mild alkaline hydrolysis. The two major acids were isolated and identified by nmr as 3 alpha, 20 alpha-dihydroxy-5 alpha-and 3 alpha, 20 alpha-dihydroxy-5 beta-pregnan-21-oic acids. Two minor C21 components were identified as 3 alpha, 20 beta-dihydroxy-5 beta-pregnan-21-oic and 3 beta, 20 alpha-dihydroxypregn-5-en-21-oic acids. A trace amount of 3 alpha, 20 beta-dihydroxy-5 alpha-, 3 beta, 20 alpha-dihydroxy-5 alpha-pregnan-21-oic, and 3 beta, 20 beta-dihydroxypregn-5-en-21-oic acids were also detected. The identification of these C21 acids was confirmed by mass spectral and chromatographic comparison with standards of eight saturated and two 5-unsaturated 3, 20-dihydroxylated C21 acids. The decisive predominance of 20 alpha isomers confirmed the native presence of C21 acids in meconium. Six acids, with an exception of 3 beta, 20 beta-dihydroxy-pregn-5-en-21-oic acid, were detected in the extract of meconium prepared in the presence of large excess of sodium borohydride; this minor acid, together with a part of its 20-epimer, was evidently formed as result of the artefactual oxidation of 21-hydroxypregnenolone, the known constituent of meconium. The co-occurrence of relatively high concentrations of C21 acids and monohydroxylated C20 acids, previously detected in human meconium, pointed to the significance of the oxidative catabolism of neutral C21 steroids in the case of feto-placental-maternal unit.