ABSTRACT
Flavonoids are constituents of the human diet (they are present in many beverages and food), and in organisms they are responsible for several biological functions, including that of antioxidant. Because of the increasing interest in these molecules, methods for their synthesis and structural modification are of great importance; studies on the biological activities of many of these compounds are insufficient because of their scarcity and/or high cost. We have developed an expeditious synthesis of polyoxygenated flavones, starting from available and inexpensive flavanones, using a bromination-methoxylation procedure. A series of flavonoids that are not otherwise accessible can be prepared using this method. As an example, 3'-demethoxysudachitin, a limited flavone possessing antimicrobial activity against methicillin-resistant Staphylococcus aureus and Helicobacter pylori and acting as a 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenger, was prepared in fairly satisfactory yield.
Subject(s)
Antioxidants/chemical synthesis , Flavanones/chemistry , Flavones/chemical synthesis , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Antioxidants/chemistry , Chemistry, Pharmaceutical/methods , Flavones/chemistry , Flavonoids/chemical synthesis , Flavonoids/chemistry , Glycosides/chemical synthesis , Glycosides/chemistry , Models, Chemical , Molecular StructureABSTRACT
Quercetin-3-O-acyl esters (I-VI) were synthesized and their usefulness as quercetin topical prodrugs was evaluated. Quercetin esters were assayed to determine their water stability and solubility, their susceptibility to undergoing enzymatic hydrolysis and their permeation through excised human skin. Quercetin ethyl (I) and hexyl (IV) esters proved poorly stable in aqueous media and they were not assayed further. Among the derivatives tested, quercetin propyl (II) and butyl (III) esters were more water-soluble than the parent drug. Esters II, III and V were readily hydrolyzed by human plasma and esters II and III penetrated excised human skin better than quercetin from aqueous saturated solutions. On the basis of the results obtained, esters II and III could be regarded as promising quercetin topical prodrugs.
Subject(s)
Esters/chemistry , Flavonoids/chemistry , Prodrugs/chemistry , Quercetin/chemistry , Administration, Cutaneous , Chromatography, High Pressure Liquid , Drug Stability , Esters/chemical synthesis , Flavonoids/chemical synthesis , Half-Life , Humans , Hydrolysis , Hydrophobic and Hydrophilic Interactions , Permeability , Prodrugs/chemical synthesis , Prodrugs/pharmacokinetics , Quercetin/pharmacokinetics , Skin/metabolism , Skin Absorption , Solubility , Structure-Activity RelationshipABSTRACT
Neither quercetin (Q), nor 3-O-acylquercetines, up to 100 microg/mL, had any significant activity on selected gram-positive strains (Staphylococcus aureus, Bacillus subtilis, Listeria ivanovi, Listeria monocytogenes, Listeria serligeri), gram-negative strains (Escherichia coli, Shigella flexneri, Shigella sonnei, Salmonella enteritidis, Salmonella tiphymurium) and yeasts (Candida albicans and Candida glabrata). In addition, we confirmed the known anti-HIV activity of Q (80% inhibition at 40 microM), which might depend on the free hydroxyl in the C-3 position, as suggested by the lack of activity of the 3-O-acylquercetines. Finally, we described an interesting inhibitory activity on Candida rugosa lipase by Q (IC(16)=10(-4) M) and its esters (3-O-acylquercetines) which, in vivo, could play an important role against lipase producing microorganisms. In particular, 3-O-acyl-quercetines, being more active (IC(16)=10(-4)-10(-6) M) and more lipophilic, could be more effective than Q when applied to the skin or mucosae, and deserve to be studied further.
