Fundamental study of the ultrasonic induced degradation of the popular antihistamine, diphenhydramine (DPH).

Diphenhydramine (DPH) the active ingredient in Benadryl, has been detected in streams, rivers and other surface water sources. As a bioactive compound, DPH impacts human health even at low concentrations. Ultrasonic irradiation at 640 kHz leads to the rapid degradation of DPH in aqueous solution. Radical scavenging experiments and detailed product studies indicate the DPH degradation involves direct pyrolysis and degradation reactions mediated by the hydroxyl radicals produced during cavitation. The degradation can be modeled by pseudo-first order kinetics yielding rate constants k of 0.210, 0.130, 0.082, 0.050, 0.035, 0.023 min-1 at the initial concentrations of 2.8, 5.2, 13.9, 27.0, 61.0, 160.0 µmol L-1, respectively. The degradation process follows the Langmuir-Hinshelwood (heterogeneous) model with a partition coefficient, KL-H = 0.06 µmol·L-1and reactivity constant kr = 1.96 µmol min-1·L-1. A competition kinetic study conducted employing the hydroxyl radical trap, coumarin, illustrates that DPH was degraded primarily by hydroxyl radical mediated processes. Computational studies employing Gaussian 09 basis set provide fundamental insight into the partitioning of the reaction pathways and the degradation mechanisms. The study demonstrates the ultrasonic degradation of DPH is rapid, follows simple kinetic expressions and is accurately modeled using computational methods.

Development of a brain nucleus involved in song production in zebra finches (Taeniopygia guttata) is disrupted by Aroclor 1248.

We studied whether polychlorinated biphenyls (PCBs) may alter the development of song control brain nuclei in zebra finch (Taeniopygia guttata) offspring of pulse-exposed hens. We orally administered 40 microg of Aroclor 1248 to adult female finches before egg laying. When the progeny were 50 d old, we measured the volumes of the song control nuclei robustus arcopallialis (RA) and higher vocal center (HVC) using light microscopy. Both male and female progeny of exposed birds had a significantly smaller RA than control birds (36 and 16%, respectively; p < or = 0.05). The HVC did not differ in either sex between exposed and control groups. Perhaps impaired development of RA was caused by PCB action on steroid receptors. We conclude that animals living in contaminated areas may be at risk of neurological damage in hormone-sensitive brain areas and that changes in brain nuclei related to song may be a sensitive indicator of low-level PCB exposure.