Vitamin K supplementation during pregnancy for improving outcomes: a systematic review and meta-analysis
Authors: Shahrook, Sadequa; Ota, Erika; Hanada, Nobutsugu; Sawada, Kimi; Mori, Rintaro
To study supplementation effect of vitamin K (VK) alone or combined with other nutrients administered to pregnant women, we searched Cochrane Pregnancy and Childbirth Group's Trials Register (till 22 January 2016, updated on 28 February 2018) including other resources. Two review authors independently assessed randomised or quasi-randomised controlled trials for inclusion, data extraction, accuracy, and risk of bias. We included older trials from high-income countries (six; 21,493 women-newborns), judged mostly as high or unclear bias risk. We could not assess high-risk e.g. epileptic women, but healthy women (different gestational ages) received varying VK dosages and duration. We meta-analysed neonatal bleeding (RR 1.16, 95% CI 0.59 to 2.29; P = 0.67) and maternal plasma VK1 (MD 2.46, 95% CI 0.98 to 3.93; P = 0.001). We found many outcomes were un-assessed e.g. perinatal death, maternal bleeding, healthcare utilization. Mostly newborns were included where VK found significantly effective for e.g. serum VK (mother-newborn), maternal breast milk VK. Few trials reported neonatal adverse side effects. The GRADE evidence quality was very low i.e. neonatal bleeding, neonatal jaundice, maternal plasma VK1. The intervention was favourable for maternal sera VK1 but remained uncertain for neonatal bleeding and other outcomes. The existing literature gaps warrant future investigations on un-assessed or inadequately reported outcomes.
Electron and proton transferring properties of vitamin K-1 across a self-assembled phospholipid monolayer
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
Authors: Herrero, R; Buoninsegni, FT; Becucci, L; Moncelli, MR
The electrochemical behaviour of vitamin K-1 (VK1) incorporated in a self-assembled monolayer of dioleoylphosphatidylcholine (DOPC) deposited on a hanging mercury drop electrode was investigated by a computerized chronocoulometric technique. The kinetics of VK1 electroreduction to the corresponding quinol, VK1H(2), and that of VK1H(2) reoxidation to VK1 were examined for reactant concentrations ranging from 0.5 to 2 mol% by varying the pH from 5.5 to 9 with phosphate and berate buffers. On the basis of a general kinetic approach it was concluded that the reduction of VK1 to VK1H(2) in a DOPC monolayer takes place via the reversible uptake of one electron, yielding the semiquinone radical anion VK1(.-), followed by the rate determining protonation of the latter. On the other hand, the oxidation of VK1H(2) to VK1 takes place via the reversible release of one electron, yielding the semiquinone radical cation VK1H(2)(+.), followed by the rate determining deprotonation of the latter. The only effective proton donors in VK1 reduction are the protons, whereas the main proton accepters in VK1H(2) oxidation are the water molecules. (C) 1998 Elsevier Science S.A. All rights reserved.