Synthesis and Antimicrobial Activity of Ursolic Acid Ester Derivatives.

Infections caused by microorganisms are a major cause of morbidity and mortality worldwide, and natural products continue to be important sources for the discovery of new antimicrobial agents. Ursolic acid is a triterpene with known antibacterial action, being naturally found in plants, such as Jaracanda oxyphylla and Jacaranda caroba (Bignoniaceae). Ursolic acid derivative esters have revealed potential biological activities, such as antitumor, antiviral, and antibacterial activity. In this study, sixteen esters (1-16) were synthesized from ursolic acid using DIC/DMAP and characterized by infrared (IR), nuclear magnetic resonance (1 H- and 13 C-NMR) and mass spectrometry. All ursolic acid esters were evaluated against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and the yeast Candida albicans. Six compounds are herein described for the first time (3, 9, 11, 13, 14 and 16) with yields up to 91.6 %. Compounds 11 (3ß-(3,4-dimethoxybenzoyl)ursolic acid) and 15 (3ß-nicotinoylursolic acid) displayed promising antifungal activity, with inhibition of C. albicans growth of 93.1 and 95.9 %, respectively.

Microwave-assisted synthesis of borneol esters and their antimicrobial activity.

Seventeen borneol esters (1-17) were synthesised by conventional and microwave-assisted methodology using DIC/DMAP, and seven are described for the first time (8, 9, 10, 12, 13, 16 and 17). The microwave-assisted methodology was carried out without use of solvents, displayed short reaction times, and showed equal or higher yields for all the long-chain esters and three aromatic compounds (11, 12 and 14) when compared to the conventional approach. All the borneol esters were evaluated against the bacteria Streptococcus sanguinis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and the fungus Candida albicans. Compounds 12, 13 and 14 displayed promising antibacterial activity with a MIC equal to ampicilin (62.5 mg mL-1) for some microorganisms. In fact, bornyl 3',4'-dimethoxybenzoate (13) was active against all tested bacteria and fungus.

Pentacyclic triterpenes and steroids from the stem bark of uchi (Sacoglottis uchi, Humiriaceae) / Triterpenos pentacíclicos e esteróides da casca do uchi (Sacoglottis uchi, Humiriaceae)

The ethanol extract from stem bark of Sacoglottis uchi Huber (popularly known as “uchi” in the Amazon Region) was submitted to chromatographic fractionation. The dichloromethane fractions provided the pentacyclic triterpene 3-oxo-friedelin (1). The dichloromethane:methanol fractions provided the pentacyclic triterpenes pseudotaraxasterol (2), lupeol (3), a-amyrin (4), betulin (5), and methyl 2ß,3ß-dihydroxy-urs-12-en-28-oate (6) and a mixture of the steroids sitosterol (7) and stigmasterol (8). Their chemical structures were determined by NMR spectroscopy and comparison with spectroscopic data from the literature. All compounds are described for the first time in this species.

O extrato etanólico da casca do caule de Sacoglottis uchi Huber (conhecida popularmente como “uchi” na Amazônia) foi submetido a fracionamento cromatográfico. As frações eluídas com diclorometano forneceram o triterpeno pentacíclico 3-oxo-friedelina (1). As frações em diclorometano:metanol forneceram os triterpenos pentacíclicos pseudotaraxasterol (2), lupeol (3), a-amirina (4), betulina (5) e 2ß,3ß-di-hidroxi-urs-12-en-28-oato de metila (6), além de uma mistura dos esteróides sitosterol (7) e estigmasterol (8). Suas estruturas químicas foram determinadas por espectroscopia de RMN e comparação com os dados espectroscópicos descritos na literatura. Todas as substâncias isoladas são descritas pela primeira vez nesta espécie.