Obtenção e caracterização de frações purificadas de saponinas de chenopodium quinoa e avaliação da formação de complexos do tipo iscom : atividades biológicas das frações e dos complexos formados

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

2011

RESUMO

Chenopodium quinoa (quinoa) seeds are a rich protein source and well-known for their high saponin content. Chemically, quinoa saponins are triterpene glycosides being phytolaccagenic, hederagenin, oleanolic and serjanic acids the most common aglycones found in seeds. Its immunoadjuvant properties have been examined and the results obtained were conflicting. Mixed micelles composed of saponin, cholesterol and phospholipids, either containing antigen (ISCOM) or not (ISCOM matrix), have been under intensive development in recent years due to their ability to act as antigen presenting-carriers with remarkable immunostimulating properties. The formation of ISCOM or other clearly defined micellar structures with quinoa saponins remained uncorroborated. The objectives of this study were the chemical structure characterization of main saponins present in C. quinoa seeds and the evaluation of antifungal and immunoadjuvant properties related to them. Also, micellar aggregates formed by self-association in aqueous solutions by quinoa saponins as well as nanostructures formed after their complexation with cholesterol (CHOL) and phosphatidylcholine (PC) were evaluated. The separation method of quinoa saponins using a polyaromatic resin allowed the preparation of two purified and enriched fractions, FQ70 and FQ90. Ten triterpenic saponins were chemically characterized by UPLC/Q-TOF-MS in quinoa saponin fractions. A LC-method was developed and validated aiming the saponin content assay in quinoa saponin fractions. The antifungal activity of quinoa fractions was evaluated by broth microdilution method for the determination of the minimal inhibitory concentration (MIC). Both fractions were inactive against all yeasts tested. However all dermatophyte fungi were susceptible to quinoa saponin fractions. The aggregates formed by self-association in aqueous solutions by two quinoa saponin fractions, as well as several distinctive nanostructures formed after their complexation with cholesterol and phosphatidylcholine at different ratios were studied. Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) showed novel nanosized spherical vesicles formed by self-association and worm-like micelles in quinoa saponin fractions. When experimental conditions, similar to those reported for the preparation of Quillaja saponaria ISCOM matrices, tubular and ring-like micelles arose from quinoa saponin fractions. The saponin composition of quinoa fractions seems determines the nanosized structures viewed by TEM. The toxicity of quinoa fractions were assayed by haemolytic, toxicity to brine shrimps, and acute toxicity in mice tests. FQ70 was almost atoxic however, for FQ90 presented toxicity against shrimps. The quinoa saponin fractions were less haemolytic than Quil A (purified extract from Q. saponaria). To evaluate immunoadjuvant activity, mice were immunized subcutaneously with ovoalbumin (OVA) alone or adjuvanted with Quil A (adjuvant control), FQ70 or FQ90. Delayed-Type Hypersensitivity (DTH) were assayed 28 days post-priming and Concanavalin A (Con A)-, Lipopolysaccharide-, and OVA-stimulated splenocyte proliferation were also measured 28 days post-priming. The results suggested that the two quinoa saponin fractions enhanced significantly the production of humoral and cellular immune responses to OVA in mice.

ASSUNTO(S)

chenopodium quinoa chenopodium quinoa quinoa saponins antifungal saponinas atividade imunoadjuvante uplc/q-tof-ms atividade antifúngica cholesterol chenopodiaceae phosphatidylcholine immunoadjuvant toxicity

ACESSO AO ARTIGO

Documentos Relacionados