Of ginkgolic acid

Satyan KS, Jaiswal AK, Ghosal S, Bhattacharya SK. (1998). Anxiolytic activity of ginkgolic acid conjugates from Indian Ginkgo biloba. Psychopharmacology (Berlin). 136(2) 148-52. 

Hausen BM. The sensitizing capacity of ginkgolic acids in guinea pigs. Am J Contact Derm 1998 9 146-148. 

Fuzzati N, Pace R, Villa F. A simple HPLC-UV method for the assay of ginkgolic acid in ginkgo biliba extract. Fitoterapia 2003 74 247-256. 

Alkylation routes have been used for the monoenes in this group. Thus, ethyl 2-methoxy-6-methylbenzoate as the carbanion (formed from lithium di-isopropylamide) has been alkylated with (Z) 1-bromotetradec-7-ene in the presence of hexamethylphosphoric triamide. Demethylation with lithium t-butytthiolate yielded (15 1)-anacardic acid (ref. 114). A more activated benzyl group having an adjacent sulphur atom was used for a synthesis of the 10(Z)-isomer of ginkgolic acid in the following way (ref. 8). 

Figure 1 Structures of (A) ginkgolide A, ginkgolide B, bilobalide, (B) flavonolgly-cosides (R=H kaempferol-3-O-rutinoside R=OH quercetin-3-O-rutinoside R=0CH3 isorhamnetin-3-O-rutinoside) and (C) ginkgolic acids (R=Ci3H27, C15H31, C15H29, C15H33).

The isomer of Fig (2)-2, anacardic acid 8(E)-monoene has been synthesised by a Xrans elimination reaction as depicted in Scheme 2 [234], which also depicts the route used for the (Z)- isomer, ginkgolic acid. [235],... 

In addition to the above substances, a large variety of polysaccharides, long-chain hydrocarbons, alcohols, and acids have been isolated, as well as (Z,Z)-4,4 -(1, 4-pentadiene-l, 5-diyl) diphenol and 6-hydroxykynurenic acid [1, 2]. The cytotoxic, mutagenic, and allergenic potential of some constituents, especially anacardic or ginkgolic acids, limits the use of a crude leaf extract for therapeutical... 

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. 

Apart from cardanol (Fig. 1-1,2,4, and 5) which collectively is a minor natural component in Anacardium occidentale, the first 3-substituted monohydric phenols isolated were, ginkgol (identical with cardanol monene), (depicted in Fig. 1-2), from Ginkgo biloba, and camnospermanol, (Fig. 1-6), from Camnospermum auriculata. More recently a number of 4-substituted monohydric phenols, (depicted in Fig.l), have been obtained from natural sources including, elenic acid, R-2,4-dimethyl-22-(4-hydroxyphenyl)-docos-3(E)-enoic acid, 7, navenone,... 

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