Soyalkaloid A was isolated from Portulaca oleracea L. for the first time in our laboratory and then a rapid and sensitive ultra-high-performance liquid chromatography electrospray ionization quadrupole-time of flight mass spectrometry (UHPLC-ESI-Q-TOF/MS) method with hesperidin as internal standard (IS) was developed and validated to investigate the pharmacokinetics of soyalkaloid A in rats after oral and intravenous administrations. The analysis was achieved on an Agilent Zorbax Eclipse Plus C(18) Column (2.1 x 50 mm, 1.8 mum) by elution with acetonitrile and water (containing 0.1% formic acid), at a flow rate of 0.3 mL/min. The MS analysis was performed in the positive ion mode with monitored ion m/z 227.0814 [M + H](+) and 611.1971 [M + H](+) for soyalkaloid A and IS, respectively. The linear range was established over the concentration range 7.5-6000 ng/mL (r = 0.9951). The intra- and inter-assay accuracy and precision were between -4.86-4.49 and 1.93-9.66, respectively. The lower limits of detection and quantitation observed were 2.1 and 7.4 ng/mL, respectively. The rapid, sensitive and specific UHPLC-ESI-Q-TOF/MS method was successfully applied to a pharmacokinetic study of soyalkaloid A. Moreover, its antioxidant was studied via a 1,1-diphenyl-2-picryl-hydrazyl radical scavenging assay, the IC(50) value being 20.73 +/- 0.51 muM. CI - (c) 2018 John Wiley & Sons, Ltd.