Hydrolysis and transesterification of parabens in a aqueous solution in the presence of glycerol and boric acid
Abstract
In a solution containing 0.067 % methylparaben, 0.033 % propylparaben, 3.4 % glycerol and 2.0 % boric acid, concentrations of both parabens, 4-hydroxybenzoic acid and 2,3-dihydroxypropyl 4-hydroxybenzoate were monitored after up to 68 months storage. 4-hydroxybenzoic acid is the main hydrolysis product of parabens, while 2,3-dihydroxypropyl 4-hydroxybenzoate was proposed as the main product of transesterification of parabens with glycerol. Results of an HPLC evaluation of parabens, 4-hydroxybenzoic acid and 2,3-dihydroxypropyl 4-hydroxybenzoate showed that the decomposition of 68 months old samples stored at the room temperature did not exceed 2.0 %. The stability of both parabens in a medicinal preparation of the stated composition has thus been satisfactorily demonstrated after more than 5 years storage under ambient conditions. The transesterification reaction was shown to influence the chemical stability of parabens to an extent comparable to hydrolysis. Moreover, the presence of 2,3-dihydroxypropyl 4-hydroxybenzoate in the solution containing glycerol and boric acid was confirmed by 1H-NMR spectroscopy.- Figure 1 Reaction of GLY with BOA.
- Figure 2 Possible decomposition reactions of MP and PP in aqueous solution in the presence of GLY.
- Figure 3 Reaction scheme of preparation of 2,3-dihydroxypropyl 4-hydroxybenzoate (2,3-diOHPP)
- Figure 4 A chromatogram of the mixture initially containing 1.2 ?g mL-1 2,3-diOHPP, 3.5 ?g mL-1 4-HYB, 6.3 ?g × mL-1 MP and 2.5 ?g × mL-1 PP (see Experimental for detailed conditions)
- Figure 5 A plot of dependence of total decomposition of MP and PP, i.e. overall concentration of 4-HYB and 2,3-diOHPP, on the pH of SJ samples.
- Figure 6 A detail of the 1H-NMR spectrum of the evaporation residue of the ethyl acetate extract of the sample of SJ No. 3 measured in deuterium oxide – the region of aliphatic hydrogens. Chemical shifts of ester methylene and methine groups of 2,3-diOHPP
- Figure 7 The “aliphatic region” of 1H-NMR spectra of a saturated solution of 2,3-diOHPP in deuterium oxide. Particular multiplets are assigned to corresponding hydrogens by arrows.
Published
2011-06-28
How to Cite
FARSA, Old?ich; ?UBERT, Jan; MARE?KOV, Marie.
Hydrolysis and transesterification of parabens in a aqueous solution in the presence of glycerol and boric acid.
Journal of Excipients and Food Chemicals, [S.l.], v. 2, n. 2, p. 41-49, june 2011.
ISSN 21502668.
Available at: <https://ojs.abo.fi/ojs/index.php/jefc/article/view/87>. Date accessed: 27 dec. 2024.
Issue
Section
Original Research Articles
Keywords
Parabens; glycerol; boric acid; transesterification; hydrolysis; 2,3-dihydroxypropyl 4-hydroxybenzoate; 1H-NMR
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