Analysis for Alpha-Pyrrolidinovalerophenone and Its 2-Oxo-PVP Metabolite in Plasma by Liquid Chromatography-Tandem Mass Spectrometry.

Alpha-pyrrolidinovalerophenone (alpha-PVP), a novel psychoactive substance, has widespread recreational use. This with interest in its pharmacological effects creates a need for methods that measure alpha-PVP concentrations. We therefore developed a LC-MS/MS method that can quantitate alpha-PVP and 2-oxo-PVP in rat plasma using a 0.1-mL sample volume. Addition of internal standards (2.5 ng/mL alpha-PVP-d8/2-oxo-PVP-d6) was followed by liquid-liquid extraction with 1-chlorobutane:acetonitrile (4:1), evaporation and reconstitution with 0.1% formic acid. Extracts were analyzed by LC-MS/MS using an Agilent 1100 HPLC and a Thermo Scientific TSQ Quantum Access MS/MS, with a YMC ODS-AQ, 50 mm × 2 mm, 3 µm column. The mobile phase was 0.1% formic acid:acetonitrile gradient at a 0.2-mL/minute flow rate with positive ion electrospray. SRM was used for the analysis with transitions: alpha-PVP, 232 â†’ 91; alpha-PVP-d8, 240 â†’ 91; 2-oxo-PVP, 246 â†’ 91; 2-oxo-PVP-d6, 252 â†’ 91. Alpha-PVP and 2-oxo-PVP eluted at 6.4 and 8.9 min. Calibrators range from 0.25 to 500 ng/mL. Accuracy and precision evaluated quality control samples prepared at 0.75, 10 and 400 ng/mL. The intra-assay evaluation also included the 0.25-ng/mL LOQs prepared in six different blank plasma sources. The intra-assay accuracy ranged from 88.9 to 117.8% of the target, and the intra-assay precision ranged from 0.9 to 16.0%. The inter-assay accuracy ranged from 98.7 to 110.7% of the target, and the inter-assay precision ranged from 4.5 to 12.0%. Extraction recovery was at least 52% for alpha-PVP and 67% for 2-oxo-PVP. Ionization recoveries were at least 64% for alpha-PVP and 82% for 2-oxo-PVP. These losses did not adversely affect assay performance. Alpha-PVP and 2-oxo-PVP controls were stable at room temperature for up to 24 h and frozen for at least 36 days. Alpha-PVP and 2-oxo-PVP were also stable in processed samples (extracts) stored at room temperature for at least 24 days. The procedure was used to analyze rat plasma samples from a pharmacokinetic study.

Reply to Van Valkenburgh et al.

DeSantis et al. respond to the concerns raised by Van Valkenburgh et al. on their original study.

Causes and Consequences of Pleistocene Megafaunal Extinctions as Revealed from Rancho La Brea Mammals.

The fossils preserved in the Rancho La Brea "tar" seeps in southern California span the past ∼50,000 years and provide a rare opportunity to assess the ecology of predators (e.g., the American lion, sabertooth cats, cougars, dire wolves, gray wolves, and coyotes), including clarifying the causes and consequences of the terminal Pleistocene extinction event. Here, a multi-proxy approach elucidates dietary responses of carnivorans to changing climates and megafaunal extinctions. Using sample sizes that are unavailable anywhere else in the world, including hundreds of carnivoran and herbivore specimens, we clarify the paleobiology of the extinct sabertooth cats and dire wolves-overturning the idea that they heavily competed for similar prey. Canids (especially the dire wolf) consumed prey from more open environments than felids, demonstrating minimal competition for prey throughout the latest Pleistocene and largely irrespective of changing climates, including just prior to their extinction. Coyotes experienced a dramatic shift in dietary behavior toward increased carcass utilization and the consumption of forest resources (prey and/or plant resources) after the terminal Pleistocene megafaunal extinction. Extant predators' ability to effectively hunt smaller prey and/or utilize carcasses may have been a key to their survival, especially after a significant reduction in megafaunal prey resources. Collectively, these data suggest that dietary niches of carnivorans are not always static and can instead be substantially affected by the removal of top predators and abundant prey resources.