Table 2

Structural identification of E2 metabolites

E2 Standards and MetabolitesRetention Times on HPLCRetention Times on GCCharacteristic Mass Fragments ( m/z ) of the Trimethylsilylated E2Metabolites2-bQuality of Match
StandardMetaboliteStandardMetabolite
min (RRT2-a ) min %
E1 50.27  (1.038)50.30  (1.039)25.6625.55342, 257, 218, 7399
2-OH-E1 40.50  (0.833)40.80  (0.842)30.5130.45430, 7398
4-OH-E1 41.90  (0.862)42.20  (0.871)32.1632.11430, 7398
6α-OH-E1 22.00  (0.453)N.D.29.69N.D.430, 340, 73
6β-OH-E1 23.87  (0.491)24.63  (0.509)28.0628.18430, 415, 340, 280, 7397
6-keto-E1 32.40  (0.664)N.D.33.50N.D.356, 341, 299, 73
7α-OH-E1 20.80  (0.428)N.D.26.78N.D.430, 340, 312, 283, 73
7β-OH-E1 19.80  (0.407)N.D.30.44N.D.430, 414, 340, 312, 73
11α-OH-E1 22.80  (0.469)N.D.28.71N.D.430, 415, 340, 242, 218, 73
11β-OH-E1 29.98  (0.614)N.D.28.18N.D.430, 415, 340, 313, 242, 73
11-keto-E1 31.83  (0.651)N.D.26.69N.D.356, 340, 312, 218, 73
12β-OH-E1 29.33  (0.603)N.D.30.14N.D.430, 415, 323, 218, 73
14-OH-E1 21.33  (0.439)N.D.32.83N.D.340, 325, 312, 297, 284, 73
15α-OH-E1 20.63  (0.424)N.D.31.93N.D.430, 415, 286, 217, 73
15β-OH-E1 26.53  (0.546)N.D.30.88N.D.430, 286, 218, 73
16α-OH-E1 25.37  (0.522)24.63  (0.509)31.8131.49430, 415, 286, 7396
16β-OH-E1 25.10  (0.516)24.63  (0.509)32.5532.84430, 415, 286, 7399
16-keto-E1 35.70  (0.731)N.D.32.17N.D.356, 341, 286, 232, 73
E2 48.60  (1.00)48.43  (1.00)26.7126.66416, 401, 326, 298, 285, 7399
2-OH-E2 37.17  (0.765)36.90  (0.762)31.8832.09504, 7399
4-OH-E2 34.80  (0.716)34.67  (0.716)33.9233.87504, 7399
6α-OH-E2 11.23  (0.232)10.50  (0.217)31.3931.46504, 414, 324, 309, 283, 7383
6β-OH-E2 19.57  (0.403)19.30  (0.398)30.0929.81504, 414, 324, 283, 229, 7399
6-keto-E2 24.80  (0.510)24.63  (0.509)35.8435.78430, 415, 340, 299, 129, 7396
7α-OH-E2 10.47  (0.215)10.50  (0.217)26.8126.89504, 414, 324, 309, 283, 7399
7β-OH-E2 11.67  (0.241)N.D.31.66N.D.504, 414, 324, 309, 283, 73
11α-OH-E2 20.70  (0.426)N.D.28.91N.D.504, 489, 414, 324, 217, 73
11β-OH-E2 29.22  (0.597)N.D.27.63N.D.504, 414, 324, 297, 244, 73
12β-OH-E2 30.30  (0.623)31.17  (0.640)35.4035.45504, 399, 324, 283, 7396
12-keto-E2 28.37  (0.584)N.D.32.25N.D.430, 415, 340, 323, 73
14-OH-E2 12.57  (0.259)N.D.32.53N.D.414, 324, 309, 283, 73
15α-OH-E2 9.47  (0.195)9.33  (0.193)31.8531.96504, 324, 298, 245, 217, 7396
15β-OH-E2 17.57  (0.361)17.17  (0.355)30.7230.81504, 325, 298, 283, 217, 7399
16α-OH-E2 (E3) 15.83  (0.321)15.67  (0.323)35.2035.09504, 386, 345, 324, 311, 7399
16β-OH-E2 27.87  (0.575)27.80  (0.574)36.7436.52504, 489, 386, 345, 311, 7399
16-keto-E2 23.78  (0.487)24.63  (0.509)33.3833.22430, 415, 312, 285, 258, 7389
16α-OH-17α-E2 30.55  (0.625)N.D.34.20N.D.504, 489, 414, 386, 345, 73
16β-OH-17α-E2 15.87  (0.325)N.D.32.60N.D.504, 489, 386, 345, 311, 73
2-OH-E3 7.15  (0.146)N.D.41.70N.D.592, 147, 129, 73
6-keto-E3 7.40  (0.152)N.D.49.44N.D.518, 325, 245, 73
15α-OH-E3 7.27  (0.149)N.D.46.94N.D.592, 502, 191, 73
2-MeO-E2 50.80  (1.045)N.D.30.80N.D.446, 431, 416, 315, 73

Human liver microsomes were incubated with E2 under conditions as described under Materials and Methods. Each peak was collected from the HPLC, derivatized with BSTFA containing 1% TMCS, and then analyzed by GC/MS as described under Materials and Methods.

  • N.D., Not detected.

  • 2-a  Relative retention time in relation to E2.

  • 2-b  The major fragment (base peak) for each metabolite is underlined.