Polyisoprenylated benzophenone derivatives

CHEMISTRY AND BIOLOGICAL ACTIVITY OF POLYISOPRENYLATED BENZOPHENONE DERIVATIVES... 

Bronianone, a yellow pigment present in the stem wood of G. hombroniana was the first member of polyisoprenylated benzophenone derivatives isolated from Clusiaceae [2]. This compound contains maclurin moiety, the 2,4,6,3, 4 -pentahydroxy benzophenone (2). The structure proposed initially was revised and suggested as (1) finally. 

We proposed to group PBDs that present a bicyclo-[3.3.1]-nonane-2,4,9-trione system in accord with benzoyl moiety position type A if it is on C-l, type B if it is on C-3 and finally type C if it is on C-5, Fig.(5) [40]. The structures previously reported as type C, nemorosone and 7-epinemorosone, have been corrected and all polyisoprenylated benzophenones derivatives with a bicyclo-[3.3.1]-nonane-2,4,9-trione system isolated, therefore, are derivatives of type A or B [18,19]. 

Some PBDs show up to 6 isopentenyl groups although no complicated arrangements are observed in these structures. Many of them are true examples of polyisoprenylated benzophenones because the acetate derived ring shows aromatic properties. We shall consider this group as simple benzophenone derivatives and most of them are included in Table 1. 

Porto et al. methylated a Clusia floral resin extract, chromatographed the derived compounds over silica gel, rechromatographed using preparative argentation TLC (5% silver nitrate), and thereby isolated seven polyisoprenylated benzophenones [68], Lokvam et al. [74] and de Oliveira et al. [59] also methylated a crude extract before isolating chamones I, II (119, 116), and nemorosone 11 (89) from Clusia species. 

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). 

These include rhazinilam (15.4.6) 494), which inhibits the disassembly of microtubules but has a different mechanism of action than taxol, laulimalide (15.4.7) and isolaulimalide (15.4.8) 496), WS9885B (15.4.9) 497), and polyisoprenylated benzophenones such as guttiferone E (15.4.10) 497). The naturally occurring 3(2H)-furanone derivative geiparvin has been found to counteract the microtubule-assembly effects of taxol, suggesting that it is a competitive inhibitor at the taxol-binding site of tubulin 498). 

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