Identification of homoisoflavonoids in Ophiopogon japonicus alcohol extract by an LC-MS based on precise mass and tandem mass spectrometer Chemical Studies on the Constituents of Radix Ophiopogonis Vasorelaxation effects of homoisoflavonoids from Caesalpinia sappan in  rat thoracic aortic rings Identification of homoisoflavonoids in Ophiopogon japonicus alcohol extract by an LC-MS based on precise mass and tandem mass spectrometer