Pyridoxine and Pyridoxal Analogs. VII. Acid-Base Equilibria of Schiff Bases

1963 ◽  
Vol 85 (2) ◽  
pp. 188-193 ◽  
Author(s):  
Dietrich. Heinert ◽  
Arthur E. Martell
Keyword(s):  
Schiff Bases ◽  
Acid Base

Acid-base titrations of schiff bases in deuteriomethanol as studied by1H NMR

1989 ◽  
Vol 18 (7) ◽  
pp. 691-703 ◽  
Author(s):  
M. M�kel� ◽  
O. Hormi ◽  
E. Jula ◽  
T. Korpela
Keyword(s):  
Schiff Bases ◽  
Acid Base

Electrochemical and Spectrophotometric Study of the Reactions of L-Leucine with Pyridoxal and Pyridoxal Phosphate

1994 ◽  
Vol 59 (4) ◽  
pp. 768-781
Author(s):  
T. Pineda ◽  
M. Blázquez ◽  
M. Domínguez ◽  
F. Garcia-Blanco
Keyword(s):  
Amino Acid ◽  
Schiff Bases ◽  
Formation Constant ◽  
Pyridoxal Phosphate ◽  
Mercury Electrode ◽  
Quantitative Description ◽  
Spectrophotometric Study ◽  
Acid Base ◽  
Absorption Bands ◽  
Reduction Mechanisms

The reactions of L-leucine (Leu) with pyridoxal (PL) and pyridoxal-5'-phosphate (PLP) were studied over pH 6 - 13.5. Formation of the Schiff bases was indicated by UV-VIS absorption bands and reduction waves on a mercury electrode. A comparative electrochemical and spectrophotometric study on the reaction mixtures as a function of pH and the amino acid-to-aldehyde concentration ratio was carried out. Apparent formation constant, KpH and acid-base constants for the Schiff bases were obtained. Reduction mechanisms of the imines are proposed in different pH zones. The formation constant, KSo, of an unprotonated Schiff base from unprotonated species of aldehyde and amino acid was determined by voltammetry. The results are compared to those obtained in analog Schiff bases in order to improve the quantitative description of the enzymatic models.

Higher Dietary Acidity is Associated with Lower Bone Mineral Density in Postmenopausal Iranian Women, Independent of Dietary Calcium Intake

2014 ◽  
Vol 84 (3-4) ◽  
pp. 0206-0217 ◽  
Author(s):  
Seyedeh-Elaheh Shariati-Bafghi ◽  
Elaheh Nosrat-Mirshekarlou ◽  
Mohsen Karamati ◽  
Bahram Rashidkhani
Keyword(s):  
Calcium Intake ◽  
Dietary Calcium ◽  
Dietary Calcium Intake ◽  
Dietary Intakes ◽  
Iranian Women ◽  
Acid Base Balance ◽  
Mineral Density ◽  
Acid Base ◽  
Base Balance ◽  
Dietary Acid

Findings of studies on the link between dietary acid-base balance and bone mass are relatively mixed. We examined the association between dietary acid-base balance and bone mineral density (BMD) in a sample of Iranian women, hypothesizing that a higher dietary acidity would be inversely associated with BMD, even when dietary calcium intake is adequate. In this cross-sectional study, lumbar spine and femoral neck BMDs of 151 postmenopausal women aged 50 - 85 years were measured using dual-energy x-ray absorptiometry. Dietary intakes were assessed using a validated food frequency questionnaire. Renal net acid excretion (RNAE), an estimate of acid-base balance, was then calculated indirectly from the diet using the formulae of Remer (based on dietary intakes of protein, phosphorus, potassium, and magnesium; RNAERemer) and Frassetto (based on dietary intakes of protein and potassium; RNAEFrassetto), and was energy adjusted by the residual method. After adjusting for potential confounders, multivariable adjusted means of the lumbar spine BMD of women in the highest tertiles of RNAERemer and RNAEFrassetto were significantly lower than those in the lowest tertiles (for RNAERemer: mean difference -0.084 g/cm2; P=0.007 and for RNAEFrassetto: mean difference - 0.088 g/cm2; P=0.004). Similar results were observed in a subgroup analysis of subjects with dietary calcium intake of >800 mg/day. In conclusion, a higher RNAE (i. e. more dietary acidity), which is associated with greater intake of acid-generating foods and lower intake of alkali-generating foods, may be involved in deteriorating the bone health of postmenopausal Iranian women, even in the context of adequate dietary calcium intake.

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