Effects of hydroxycinnamic acids on blue color expression of cyanidin derivatives and their metal chelates.

Mechanisms to recreate many anthocyanin blue hues in nature are not fully understood, but interactions with metal ions and phenolic compounds are thought to play important roles. Bluing effects of hydroxycinnamic acids on cyanidin and chelates were investigated by addition of the acids to triglycosylated cyanidin (0-50×[anthocyanin]) and by comparison to hydroxycinnamic acid monoacylated and diacylated Cy fractions by spectrophotometry (380-700nm) and colorimetry in pH 5-8. With no metal ions, λmax and absorbance was greatest for cyanidin with diacylation>monoacylation>increasing [acids]. Hydroxycinnamic acids added to cyanidin solutions weakly impacted color characteristics (ΔE<5); while acylation (covalent acid attachment) resulted in ΔE 5-15. Triglycosylated cyanidin expressed blue color (pH 7-8), suggesting glycosylation pattern also plays a role. Al3+ chelation increased absorbance 2-42× and λmax≳40nm (pH 5-6) compared to added hydroxycinnamic acids. Metal chelation and aromatic diacylation resulted in the most blue hues.

Spectral and colorimetric characteristics of metal chelates of acylated cyanidin derivatives.

Colorants derived from nature are increasingly popular due to consumer demand. Anthocyanins are a class of naturally occurring pigments that produce red-purple-blue hues in nature, especially when interacting with metal ions and co-pigments. The role of various acylations of cyanidin (Cy) derivatives on color expression and stability of Al3+ and Fe3+ chelates in pH 6-7 were evaluated by spectrophotometry (380-700nm) and colorimetry (CIE-L∗a∗b∗) during dark, ambient storage (48h). Increased substitution generally increased λmax of Cy chelates: malonic acid monoacylationferulic-sinapic>sinapic-sinapic)>monoacylated (malonic≈sinapic>ferulic>p-coumaric).

Evaluating the role of metal ions in the bathochromic and hyperchromic responses of cyanidin derivatives in acidic and alkaline pH.

In many food products, colorants derived from natural sources are increasingly popular due to consumer demand. Anthocyanins are one class of versatile and abundant naturally occurring chromophores that produce different hues in nature, especially with metal ions and other copigments assisting. The effects of chelation of metal ions (Mg(2+), Al(3+), Cr(3+), Fe(3+), and Ga(3+)) in factorial excesses to anthocyanin concentration (0-500×) on the spectral characteristics (380-700nm) of cyanidin and acylated cyanidin derivatives were evaluated to better understand the color evolution of anthocyanin-metal chelates in pH 3-8. In all pH, anthocyanins exhibited bathochromic and hyperchromic shifts. Largest bathochromic shifts most often occurred in pH 6; while largest hyperchromic shifts occurred in pH 5. Divalent Mg(2+) showed no observable effect on anthocyanin color while trivalent metal ions caused bathochromic shifts and hue changes. Generally, bathochromic shifts on anthocyanins were greatest with more electron rich metal ions (Fe(3+)≈Ga(3+)>Al(3+)>Cr(3+)).

Monomethylethanolamine reduces plasma triacylglycerols and apolipoprotein B and increases apolipoprotein A-I rats without induction of fatty liver.

Monomethylethanolamine (MME) inhibits very low density lipoprotein (VLDL) secretion from cultured rat hepatocytes by disruption of translocation of apolipoprotein (apo) B across the endoplasmic reticulum membrane (A. E. Rusiñol, E. Y. W. Chan and J. E. Vance. 1993. J. Biol. Chem. 268: 25168-25175). We have now investigated whether or not plasma levels of lipids and apoB are reduced by dietary supplementation of rats with MME. In rats fed MME for 5 to 7 days, the levels of triacylglycerols and apoB in VLDL were reduced by 66% and 45%, respectively. At the same time, MME feeding also increased plasma apoA-I by 80%. No significant differences were found in body or liver weights between control and MME-fed rats, nor did the reduction of plasma VLDL in MME-fed rats result in accumulation of triacylglycerols in the liver. When the dietary period was extended to 15 weeks, essentially the same results were obtained except that plasma cholesterol was increased by 31% in MME-treated animals, apparently because of increased amounts of apoA-I and high density lipoproteins. According to post-mortem and microscopic examination, rats fed MME for 15 weeks were anatomically normal with no indication of any lipid accumulation in the liver. The ability of MME to reduce VLDL secretion and at the same time to increase the level of high density lipoproteins are attractive properties of a therapeutic agent for treatment of atherosclerosis in humans.