This study performed quantitative identifications of phytoestrogenic compounds, such as free and conjugated isoflavones, lignans, coumestrol and various flavonoids, on six different vegetable samples by a triple quadrupole liquid chromatography-tandem mass spectroscopy (LC-MS/MS) technique following different pretreatments, such as conventional extraction (CE), acid hydrolysis (AH), enzymatic hydrolysis (EH) and enzymatic and acid hydrolysis (EAH). A comparison of sample preparation methods used as pretreatment revealed that the EH method was more effective for the identification of total isoflavone content, and the EAH method was more effective for identification of the total lignans, other flavonoids and total phytoestrogenic compound content in vegetables. It was found that secoisolariciresinol (235.5-913.8 mu g/100 g vegetable, wet weight) was the major phytoestrogenic compound in all vegetable samples. Considering the sample preparation methods that determined the highest concentration values, the total amount of phytoestrogenic compounds in green bean, carrot, cauliflower, white cabbage, iceberg lettuce and artichoke were found to be 921.7, 239.6, 228.3, 349.5, 252.7 and 259.2 mu g/100 g (wet weight), respectively. (C) 2012 Elsevier Inc. All rights reserved.