3-Methoxy-4-hydroxybenzoic

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. 

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.)...

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... 

CAS 3943-74-6 EINECS/ELINCS 223-525-9 Synonyms Benzoic acid, 4-hydroxy-3-methoxy-, methyl ester 4-Hydroxy-3-methoxybenzoic acid methyl ester Methyl 4-hydroxy-3-methoxybenzoate Methyl 3-methoxy-4-hydroxybenzoate Vanillic acid, methyl ester Empirical C9H10O4... 

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. 

The IR (1690 cm ) and UV (257 nm) spectra, and the formation of a 2,4-dinitrophenylhydrazone supported the presence of an a,p-unsaturated carbonyl group in tomentellin (581). Hydrogenation of (581) which gave methyl 3-methoxy-4-hydroxybenzoate and tetrahydroderivative, and analysis of the H-NMR and mass spectra [m/z 181 +H (65%) and 151 (100%)] led to the conclusion that tomentellin was 3,7-dimethyl-5-keto-2,6-octadienyl 3,4-dimethoxybenzoate (581). The position of the carbonyl group was further confirmed by the bathochromic shift of the UV absorption band to 257 nm after addition of aq. NaOH. The geometry of the enone system was presumed to be s-cis from the observation that the IR absorption band of the double bond was more intense than that of a carbonyl group. 

Hydrolysis of the fourth isoprenyl benzoate (584) gave vanillic acid. Methylation of (584) afforded tomentellin (581). Thus, the structure of demethoxytomentellin was established to be 3,7-dimethyl-5-keto-2,6-octa-dienyl 3-methoxy-4-hydroxybenzoate (584). 

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-... 

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