Table 2

Structural identification of E₁ metabolites formed by human liver microsomes

Identified Estrogens	Retention Times on HPLC (RRT^2-a)		Retention Times on GC		Characteristic Mass Fragments of Trimethylsilylated E₁Metabolites^2-b	Quality of Match
Identified Estrogens	Standard	Metabolite	Standard	Metabolite		Quality of Match
	min		min		m/z	%
E₁	50.27 (1.038)	50.31 (1.042)	25.66	25.51	342, 257, 218, 73	99
2-OH-E₁	40.50 (0.833)	40.04 (0.829)	30.51	30.45	430, 73	99
4-OH-E₁	41.90 (0.862)	41.60 (0.862)	32.16	32.05	430, 73	99
6α-OH-E₁	22.00 (0.453)	21.50 (0.445)	29.69	30.04	430,340, 73	80
6β-OH-E₁	23.87 (0.491)	23.74 (0.492)	28.06	28.13	430, 415, 340, 280, 73	94
6-keto-E₁	32.40 (0.664)	31.73 (0.657)	33.50	33.21	356, 341, 299, 73	70
7α-OH-E₁	20.80 (0.428)	20.00 (0.414)	26.78	27.20	430,340, 312, 283, 73	90
16α-OH-E₁	25.37 (0.522)	24.83 (0.514)	31.90	31.50	430, 415, 286, 73	99
16β-OH-E₁	25.10 (0.516)	24.83 (0.514)	32.65	32.81	430, 415, 286, 73	90
E₂	48.60 (1.00)	48.28 (1.00)	26.71	26.76	416, 401, 326, 298, 285, 73	99
2-OH-E₂	37.17 (0.765)	36.40 (0.754)	31.88	31.85	504, 73	99
4-OH-E₂	34.80 (0.716)	34.78 (0.720)	33.92	33.74	504, 73	95

Note: Human liver microsomes were incubated with E₁ under conditions as described under Materials and Methods. Each peak was collected from the HPLC, derivatized withN,O-bis(trimethylsilyl)trifluoroacetamide containing 1% trimethylchlorosilane, and then analyzed by GC/MS as described under Materials and Methods. Information for 2-MeO-E₂, 2-OH-E₃, 6α-OH-E₂, 6β-OH-E₂, 6-keto-E₂, 6-keto-E₃, 7α-OH-E₂, 7β-OH-E₁, 7β-OH-E₂, 11α-OH-E₁, 11α-OH-E₂, 11β-OH-E₁, 11β-OH-E₂, 11-keto-E₁, 12β-OH-E₁, 12β-OH-E₂, 12-keto-E₂, 14-OH-E₁, 14-OH-E₂, 15α-OH-E₁, 15α-OH-E₂, 15α-OH-E₃, 15β-OH-E₁, 15β-OH-E₂, 16α-OH-E₂, 16α-OH-17α-E₂, 16β-OH-E₂, 16β-OH-17α-E₂, 16-keto-E₁, and 16-keto-E₂ are listed in our recent article (Lee et al., 2001).

↵2-a Relative retention time in relation to E₂.
↵2-b The major fragment (base peak) for each metabolite is underlined.