Prenylated coumaric acids

Other antimicrobial phenolic compounds from the Anthemideae tribe are coumarins, which are derivatives of benzo-a-pyrone. Feresin et al. [199] isolated eight / -coumaric acid derivatives from the Argentinian medicinal plant Baccharis grisebachii. Two of them, 3-prenyl-/ -coumaric acid, Fig. (38) and 3,5-diprenyl-p-coumaric acid were active towards Epidermophyton floccosum and Trichophyton rubrum, with MIC values of 50 and 100-125 ig/ml, respectively. 

From Bolivian Baccharis species, two prenylated coumaric acids, Fig. (50) were isolated from B. boliviensis [33], while B. grisebachii, an endemic species from Argentina, yielded 3-(3,3-dimethylallyl)-/ -coumaric acid [72],... 

Fig. (50). Structure of prenylated coumaric acids isolated from Baccharis boliviensis...

Hydroxylation of p-coumaric acid, followed by photocatalyzed isomerization of the double bond and lactonization, affords 7-hydroxy coumarin (umbel-liferone). Prenylation at the 6-position, epoxidation, cyclization, and a retro-aldol reaction afford the furanocoumarins (Fig. 14) some (psoralen, bergapten)... 

Fig. (38). Structure of 3-prenyl-p-coumaric acid isolated from Baccharis grisebachii...

Propolis from Europe is the best known type of propolis. In European regions with temperate climate bees obtain resin mainly from the buds of Poplus species and the main bioactive components are flavonoids (Greenaway et al., 1990). In tropical countries, the botanical resources are much more variable in respect to temperate zones, so bees find much more possibilities of collecting resins and hence the chemical composition of tropical propolis are more variable and distinct from European ones (Sawaya et al., 2011). Different compounds have been reported in tropical propolis such as terpenoids and prenylated derivatives of p-coumaric acids in Brazilian propolis (Marcucci, 1995), lignans in Chilean samples (Valcic et al, 1998), and polyisoprenylated benzophenones in Venezuelan, Brazilian, and Cuban propolis (Cuesta-Rubio et al., 1999 Marcucci, 1995). 

Coumarin, together with o-hydroxycinnamic acid and other compounds, has been reported in wood and barks of infected stems of Prunus yedoensis (60). The simple coumarins (Table 7.1.3.A) vary in their substitution of the aromatic ring. Prenylation (i.e., dimethylallyl substitution) also contributes to the great diversity. Umbelliferone (26), aesculetin (27), and scopoletin (28) corresponding in structure to j9-coumaric, caffeic, and ferulic acid - and various types of derivatives, are the three most common hydroxycoumarins in plants, including many species... 

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