Hydroxybenzoic acid derivative

HBr, phenol, 30 min, heat, 85% yield. 4-Hydroxybenzoic acid has been used in place of phenol to aid in the isolation process. The addition of water to the reaction mixture caused most of the hydroxybenzoic acid derivatives to precipitate, thus greatly simplifying the isolation. ... 

Laccase (PCL) as well as peroxidases (HRP and SBP) induced a new type of oxidative polymerization of the 4-hydroxybenzoic acid derivatives, 3,5-dimethoxy-4-hydroxybenzoic acid (syringic acid) and 3,5-dimethyl-4-hydroxybenzoic acid. The polymerization involved elimination of carbon dioxide and hydrogen from the monomer to give PPO derivatives with molecular weight up to 1.8 x lO (Scheme 22). - ... 

Tomas-Barberan, F.A. and Clifford, M.N., Dietary hydroxybenzoic acid derivatives — nature, occurrence and dietary burden, J. Sci. Food Agric., 80, 1024, 2000. 

CLASSES OF PLANT POLYPHENOLS 1. Hydroxybenzoic acids derivatives... 

The hydroxybenzoic acid derivatives (HBAs) are phenolic compounds with a general structure C6-C1. The related C6-Ci acids (phenylacetic acids) occur occasionally as minor components of foods. 

In carrots, the principal phenolics are the hydroxycinnamic acid derivatives. Of these, caffeic acid derivatives are the main components (20-100 mg/kg fw. depending on the cultivar), while ferulic acid derivatives are accumulated in intermediate quantities (10-20 mg/kg) and p-coumaric derivatives, 4-hydroxybenzoic acid derivatives and vanillic acid are present in trace amounts [38]. The main compound in carrots is chlorogenic acid, which has been estimated as between 23 and 121 mg/kg f w. depending on the cultivar. However, in carrot tops, this compound can reach 375-400 mg/kg [40], while cryptochlorogenic, neochlorogenic and 5-feruloylquinic acids have also been detected. 

Minimal processing of carrots induces phenylalanine ammonia lyase (PAL) activity and phenolics accumulation. In shredded carrots, chlorogenic acid, which is rapidly accumulated, represents 60% of the total phenolics. In addition traces of 3 -caffeoylquinic and 4 -caffeoylquinic acids are biosynthesised, and 3, 4 -dicaffeoylquinic and 3, 5 -dicaffeoyl quinic acids also accumulate [44]. p-Hydroxybenzoic acid derivatives are also biosynthesised but more slowly, and are related to defence against microbial attack (phytoalexin response), the degree and speed of which depends on the cultivar [45],... 

Carrots can accumulate, in response to fungal infection, the coumarins 6-methoxymellein and scopoletin alongside several p-hydroxybenzoic acid derivatives [46], In carrot leaves, apigenin 7-glucoside and luteolin 7-glucoside have been detected [47]. 

FIGURE 8.1 Chemical structures of hydroxybenzoic acid derivatives. 

Many hydroxybenzoic-acid-derived (Ce-Ci) compounds (acids, esters, aldehydes, alcohols, etc.) are found in the essential oils of plants. Several essential oils have commercial importance, although many important components are readily synthesized. In many cases, the synthetic products have eclipsed the naturally occurring ones in importance. For example, vanilla extract contains vanillin (Fig. 8.18). As the user of synthetic vanilla will realize, however, synthetic substitutes often lack minor components that make natural vanilla preferable. 

Hydroxybenzoic acid derivatives,flavon-3-ols. C18 6 % acetic acid in 2 mM sodium 280, 320, [123]... 

The syntheses of telechelic, star-shaped or hyperbranched oligo- and polyesters reported in this work are based on two "a-b monomers" 3-hydroxy-benzoic acid (3-Hybe) and 3-(4 -hydroxyphenyl)propionic acid (phloretic acid, Phla). These monomers were selected for the following reasons. Polyesters of 3-Hybe melt below 200°C, and they are soluble in various organic solvents (10). Polycondensations of 2-Hydroxybenzoic acid derivatives show a high tendency to yield cyclic oligomers and substituted and imsub-... 

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