3- Methoxy-4-hydroxybenzoic acid

All cements that contain eugenol inhibit the polymerization of acrylates, and those of EBA-eugenol are no exception. In order to remedy this and other defects, Brauer and his coworkers examined alternatives to eugenol (Figure 9.7). These included the esters of vanillic acid (3-methoxy-4-hydroxybenzoic acid, HV) and syringic acid (3,5-dimethoxy-4-hydroxy-benzoic acid). Both are 3-methoxy-4-hydroxy compounds and are thus chemically related to eugenol and guaiacol. Both are solids and have to be dissolved in EBA where they form satisfactory cements with EBA zinc oxide powder. The vanillate (EBA-HV) cements are the more important. 

Ginkgo extract has no effect on the hepatic microsomal drug oxidation system, as measured by antipyrine elimination, even at doses of 400 mg per day (Duche et al. 1989). Ginkgo metabolites, the substituted benzoic acids (4-hydroxybenzoic acid conjugate, 4-hydroxyhippuric acid, 3-methoxy-4-hydroxyhippuric acid, 3,4-dihydroxybenzoic acid, 4-hydroxybenzoic acid, hippuric acid and 3-methoxy-4-hydroxybenzoic acid [vanillic acid]), are excreted in urine (Pietta et al. 1997). 

In another study, the substrate was 3,4-dihydroxybenzoic acid, and the reaction products were 3-methoxy-4-hydroxybenzoic acid and 3-hydroxy-4-methoxybenzoic acid. The substrate and the two products were separated by HPLC on a reversed-phase column (LiChrosorb) with a mobile phase of 0.05 M acetic acid in methanol-water (1 4, v/v), pH 3.2 Figure 9.12 shows the separation obtained under these conditions. 

Soils also contain a number of low-molecular-mass water-soluble aromatic acids including benzoic, 4-hydroxybenzoic, cinnamic, coumaric (4-hydroxydnnamic), caffeic (3,4-dihydroxycinnamic), ferulic (3-methoxy-4-hydroxydnnamic), and vanillic (3-methoxy-4-hydroxybenzoic) acids. It has been shown that at plausible concentrations of these (< 100 gg/1) and at pH 5.6, there is competition between these and 2,4-dichlorophenol for sorption sites on soil organic matter (Xing and Pignatello 1998). 

Methoxy-4-hydroxybenzoic acid 3-Hydroxy-4-methoxybenzoic acid 3-Methoxy-4-acetoxybenzoic acid... 

Dietmhoxybenzoic acid, ethyl ester 3-Methoxy-4-hydroxybenzoic acid, ethyl ester... 

CAS 617-05-0 EINECS/ELINCS 210-503-9 Synonyms m-Anisic acid, 4-hydroxy-, ethyl ester Benzoic acid, 4-hydroxy-3-methoxy-, ethyl ester Ethyl 4-hydroxy-3-methoxybenzoate Ethyl 3-methoxy-4-hydroxybenzoate 3-Methoxy-4-hydroxybenzoic acid, ethyl ester... 

Ginkgolic acid is a mixture of several 2-hydroxy-6-alkyIbenzoic acids, two of which (alkyl = 1-octene or 3-decene) were baseline resolved on a 45 C Cjg column (A = 308nm) with a 92/7/1 acetonitrile/water/acetic acid mobile phase [1053]. Elution was complete in 6 min and peaks of interest were well resolved from all extracted material. In a separate study, Pietta et al. [1054] isolated six metabolites (hippuric acid, 4-hydroxy- and 3-methoxy-4-hydroxyhippuric acid, 4-hydroxy-, 3,4-dihydroxy-, and 3-methoxy-4-hydroxybenzoic acid) of Ginkgo biloba leaf extracts from urine and blood samples and analyzed on a Cjg column (photodiode array detector). An 88/5/5/2 water/acetonitrile/methanol/acetic acid mobile phase generated good resolution and complete elution in 15 min. The standard used was at the 1 mg/mL level. 

The hydroxybenzoic acids that are found in various fruits and occur mostly as esters include salicylic acid (2-hydroxybenzoic acid), 4-hydroxybenzoic acid, gentisic acid (2,4-di-hydroxybenzoic acid), protocatechuic acid (3,4-dihydroxybenzoic acid), gallic acid (3,4,5-trihydroxybenzoic acid), vanillic acid (3-methoxy-4-hydroxybenzoic acid) and ellagic acid (IX, Formula 18.13), the dilactone of hexahydroxydiphenic acid (Table 18.19). Table 18.19 shows the most important sources of 4-hydroxybenzoic acid, protocatechuic acid and gallic acid. Strawberries (0.2-0.5), raspberries (1.2) and blackberries (1.9-2.0) contain higher concentrations of free and bound ellagic acid (g/kg). 

Reduction of the benzoic acid carboxyl groups yields the corresponding aldehydes and alcohols, as for instance vanilhn and vanillyl alcohol (XVII and XVIII respectively in Formula 18.18) from 3-methoxy-4-hydroxybenzoic acid and coniferyl alcohol from ferulic acid. 

Tea catechins are also degraded in the intestine by microflora. Several microbial metabolites, including 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3-methoxy-4-hydroxy-hippuric acid, and 3-methoxy-4-hydroxybenzoic acid, were observed in human urine samples 19), 5-(3, 4 -Dihydroxyphenyl)-y-... 

Phenolic acids Benzoic acid derivatives OH Caffeic acid 1 Gentisic acid Benzoic acid 1 1 Vanllic acid Protocatechuic acid 1 /7-Hydroxybenzoic acid COOH Syringic acid Hydroxy-isochromans HO. l-phenyh6,7- dihydroxy-isochroman l-(3 -methoxy-4- hydroxyphenyh6,7- dihydroxydsochroman R1... 

Figure 9.13 The determination of m- and p-O-methylated products (c,d) on a LiChro-sorb 5 RP 18 column. Also shown are 4, hydroxybenzoic acid (a) and 3-methoxy-4-hydroxybenzoic add (MHBA) (b). (From Pennings and Van Kempen, 1979.)...

Thus while the phenolic ester, methyl p-hydroxybenzoate does not react with NaHCOs/ the carboxylic acid p-methoxy-benzoic acid will and this is the basis of their separation. 

Hydroxy-l-naphthoic acid 1-Naphthoic acid 3- Hydroxy-2-naphthoic acid 3- Methoxy-2-naphthoic acid 6-Ethoxy-2-naphthoic acid 4- Hydroxybenzoic acid 1- Hydroxy-2-naphthoic acid 2- Naphthoic acid 6-Hydroxy-2-naphthoic acid 6-Methoxy-2-naphthoic acid 6-Propoxy-2-naphthoic acid 2,6-Naphthalene dicarboxylic acid... 

Dalton et al. (1989b) utilizing Mehlich 111, a mild chelating extractant, also observed that the recovery of available phenolic acids (femlic acid, vanillic acid, p-coumaric acid, p-hydroxybenzoic acid) from sterile soil (Cecil, Portsmouth and White Store) varied with soil type, horizon, time, and the type of phenolic acid added. When they allowed phenolic acids added to soil to equilibrate for 2 min before extraction, they noted a significant reduction in recovery of phenolic acids. Recovery declined with time up to 32 days. The decline was most rapid over the first 2 days. The presence of methoxy groups and acrylic side chains increased... 

Iso-rhizonic acid, 2-Methoxy-3,6-dimethyl-4-hydroxybenzoic acid (Iso-rhizoninsaure, 2-Methoxy-3,6-dimethyl-4-hydroxybenzoesaure)... 

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