Hydroxycinnamates

The stabili2ation of polyolefins used to insulate copper conductors requires the use of a long-term antioxidant plus a copper deactivator. Both A[,Ar-bis(3,5-di-/ A-butyl-4-hydroxycinnamoyl)hydra2ine (29) and 2,2 -oxamidobisethyl(3,5-di-/ A-butyl-4-hydroxycinnamate) (30) are bifimctional. They are persistent antioxidants that have built-in metal deactivators. Oxalyl bis(ben2yhdenehydra2ide) (28) is an effective copper deactivator when part of an additive package that includes an antioxidant. 

Hydroxycinnamic acid (p-coumaric acid) [501-98-4] M 164.2, m 210-213 , 214-215 , 215 pK 4.64, pKj 9.45. Crystd from H2O (charcoal). Needles from cone aqueous solutions as the anhydrous acid, but from hot dilute solutions the monohydrate acid separates on slow cooling. The acid (33g) has been recrystd from 2.5L of H2O (1.5g charcoal) yielding 28.4g of recrystd acid, m 207°. It is insol in CgH6 or pet ether. The UV in 95% EtOH has 223 and 286nm (e 14,450 and 19000 M cm ). [UV Wheeler and Covarrubias J Org Chem 28 2015 7965 Corti Helv Chim Acta 32 681 1949.]... 

Karrer and Schmid have examined the water-soluble constituents in poppy straw after extraction of the alkaloids, and have recorded the presence of -hydroxybenzaldehyde, vanillin, -hydroxystyrene, meconin and the following acids fumaric, dZ-lactic, benzoic, -hydroxycinnamic, p-hydroxybenzoic, 2-hydroxycinchoninic, vanillic, phthalic, hemipinic and m-hemipinic, with a more highly unsaturated, carboxylic acid J, b.p. 170-570-02 mm., and three unidentified substances Fa , m.p. 271-2° Wx, m.p. 310° (dec.) and Q, m.p. 260° the two latter are free from nitrogen and contain no methoxyl. 

Chemical Name Methyireserpate 3 -methoxy-4 -hydroxycinnamate Common Name —... 

The chloroform layer was dried over sodium sulfate, and the solvent was evaporated, so that there was obtained a brown amorphous matter. This was recrystalllzed from chloroform-hexane, and there was then obtained 1.0 g (78% of yield) of methyireserpate 3 -methoxy-4 -hydroxycinnamate which was characterized as pale yellow needles having a melting point of 259°C to 260°C. 

Coumarin, the lactone of o-hydroxycinnamic acid, and some of its derivatives have been isolated from many plant species 31). Thimann and Bonner 141) attributed the growth-inhibiting effects of coumarin to its action on enzyme sulfhydryl groups. Inhibitory effects of coumarin on Avena coleoptiles and pea stem sections could be overcome by 2,3-dimercaptopropanol (BAL). Coumarin has also been reported to disrupt mitosis 29,30). 

The course of the reaction has not been fully clarified. Hydrolytic and aromatization processes are probably responsible for the formation of colored or fluorescent deriva4 tives (cf. Potassium Hydroxide Reagent). For instance, sevin is converted to a-naphthalkali metal salt of the o-hydroxycinnamic acid pro- duced by hydrolytic cleavage of the pyrone ring is converted from the non-fluorescent cis- to the fluorescent trans-form by the action of long-wavelength UV light (X = 365 nm) [2]. 

When the substituent groups in the polyphosphazenes were azobenzene [719] or spiropyran [720] derivatives, photochromic polymers were obtained, showing reversible light-induced trans-cis isomerization or merocyanine formation, respectively. Only photocrosslinking processes by [2+2] photo-addition reactions to cyclobutane rings could be observed when the substituent groups on the phosphazene backbone were 4-hydroxycinnamates [721-723] or 4-hydroxychalcones [722-724]. 

Figure 6.6. Three hydroxycinnamic acids common in plants and of interest as potential sporopollenin components.

Advances in analytical procedures resulted in several reports on anthocyanins acy-lated with hydroxycinnamic acids (p-coumaric, caffeic, ferulic, sinapic, and 3,5-dihydroxycinnamic acids), hydroxybenzoic acids (p-hydroxybenzoic and gallic acids), and aliphatic acids (malonic, acetic, malic, oxalic, succinic and tartaric acids). However, not all of them were found in anthocyanins isolated from foods. Among the 44 fruits listed in Table 4.3.1, 15 presented acylated anthocyanins as did 12 of 13 vegetables shown in Table 4.3.3 and 2 of the 9 grains cited in Table 4.3.4. On the other hand, acylated anthocyanins were found in all grapes from Vitis species, although at different abundance levels, as can be seen in Table 4.3.2. A higher... 

Among the hydroxycinnamic acids, anthocyanins acylated with sinapic acid are not widespread in foods they have been isolated only in black carrots " and red cabbages." Anthocyanins that are acylated with p-hydroxybenzoic acid were only found in black carrots " and sweet potatoes. This acyl group was located within the 6 position of a glucoside moiety. 

The decarboxylation of 4-hydroxycinnamic acid to 4-hydroxystyrene, and of fernlic acid (3-methoxy-4-hydroxycinnamic acid) to 4-vinylgnaiacol by several strains of Haf-nia alvei and H. protea, and by single strains of Enterobacter cloacae and K. aerogenes (Fignre 2.7d) (Findsay and Priest 1975). The decarboxylase has been pnrihed from Bacillus pumilis (Degrassi et al. 1995). 

The metabolism of ferulic acid (3-methoxy-4-hydroxycinnamic acid) by Ent. cloacae to a nnmber of products including phenylpropionate and benzoate (Fignre 2.8) (Grbic-Galic 1986). 

Decarboxylation of aromatic carboxylic acids has been encountered extensively in facultatively anaerobic Enterobacteriaceae. For example, 4-hydroxycinnamic acid is... 

FIGURE 8.32 Decarboxylation of ferulic acid (3-methoxy-4-hydroxycinnamic acid). 

Gasson Ml, Y Kitamura, WR McLaughlan, A Narbad, AJ Parr, ELH Parsons, J Payne, MJC Rhodes, NK Walton (1998) Metabolism of ferulic acid to vanillin. A bacterial gene of the enoyl-SCoA hydratase/ isomerase superfamily encodes an enzyme for the hydration and cleavage of a hydroxycinnamic acid SCoA thioester. J Biol Chem 273 4163-4170. 

Various hydroxybenzoic and hydroxycinnamic acids are present in plants (Gross, 1981 Herrmann, 1979, 1989). Steeg and Montag (1988)... 

Herrmann, K. (1989). Occurrence and content of hydroxycinnamic and hydroxybenzoic acid compounds in foods. Crit. Rev. Food Sci. 28, 315-347. 

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