Ésteres piridínicos de sacarose: síntese, caracterização e atividade antimicrobiana. Avaliação de parâmetros de síntese por cavitação acústica.
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Data
2019-05-29
Autores
Mora Vargas, Jorge Andrés
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O interesse pelos derivados de sacarose tem aumentado nos últimos anos devido suas diferentes aplicações em diversos setores industriais (farmacêutico, bioengenharia, química, agricultura e alimentos). A sacarose é o dissacarídeo natural de maior abundância, obtida em alto grau de pureza e economia que por meio de reações orgânica permite sintetizar uma série de compostos de maior valor agregado. Os ésteres de sacarose ou sucroésteres (SEs) são uma das possibilidades de derivados deste carboidrato, pois possuem aplicações como emulsificantes, controladores microbiológicos, anti-inflamatórios, antioxidantes, entre outros. Entretanto, a baixa estabilidade em condições ácidas, térmicas e a riqueza funcional da sacarose levam a pesquisa de novos métodos de síntese de sucroderivados por reações seletivas, as quais se controle o grau de esterificação (especificamente monoacilação) e a posição de acilação no mesmo processo. Por outro lado, os ácidos picolínico, nicotínico e isonicotínico (ácidos piridínicos) têm sido estudados como agentes antimicrobianos, anticancerígenos, suplementos dietéticos, o que os torna compostos químicos de interesse fármaco-biológico ainda pouco explorados como substituintes de carboidratos. Neste estudo, foram sintetizados ésteres piridínicos de sacarose por reação de transesterificação por catálise básica homogênea (metóxido de sódio) e catálise heterogênea (óxidos metálicos mistos derivados de hidrotalcitas) assistidas por cavitação acústica a 20 kHz. Uma vez determinado o melhor catalisador na síntese de SEs (metóxido de sódio), foi empregado um planejamento experimental 32 x 2 para identificar a influência de fatores como: i) tempo de irradiação com ultrassom, ii) razão molar dos reagentes de partida e iii) temperatura do sistema, avaliados mediante a determinação do consumo de éster metílico de partida. Foram obtidos consumos ≥ 75 % e elevadas porcentagens de SEs monossubstituídos (≥ 85 %). Os regioisómeros de maior abundância de cada SEs piridínico foram isolados, caracterizados e suas propriedades foram testadas como inibidores microbianos em bactéria Gram-positiva (Staphylococcus aureus ATCC 6538) e Gram-negativa (Pseudomonas aeruginosa ATCC 9027).
Interest in sucrose derivatives has increased in recent years due to their different applications in various industrial sectors (pharmaceutical, bioengineering, chemistry, agriculture and food). Sucrose is the most abundant naturally occurring disaccharide, obtained in a high degree of purity and economical, which by means of organic reactions allows to synthesize a series of higher added value compounds. Sucrose esters (SEs) are one of the possibilities of derivatives of this carbohydrate, have applications as emulsifiers, microbiological controllers, anti-inflammatories, antioxidants, among others. However, the low stability in acidic and thermal conditions and the sucrose functional richness lead to the search for new methods of synthesis of sucroderivatives by selective reactions where the degree of esterification (specifically monoacylation) and the acylation position in the same process are controlled. On the other hand, picolinic, nicotinic and isonicotinic acids (pyridinic acids) have been studied as antimicrobial agents, anticancer agents, dietary supplements, among others, which make them chemical compounds of biological and pharmaceutical interest still little explored as carbohydrate substituents. In this study, pyridine esters of sucrose were synthesized by transesterification reaction by homogeneous basic catalysis (sodium methoxide) and heterogeneous catalysis (mixed metal oxides derived from hydrotalcites) assisted by acoustic cavitation at 20 kHz. Once the best catalyst was determined in the synthesis of SEs, a 32 x 2 experimental design was used to identify the influence of factors such as: i) irradiation time with ultrasound, ii) molar ratio of starting reagents and iii) temperature of the system, evaluated by determining the consumption of the starting methyl ester. Consumption ≥ 75% and high percentages of monosubstituted SEs (≥ 85%) were obtained. The regioisomers of greatest abundance of each pyridine SEs are isolated, characterized and proved their properties as microbial inhibitors in Gram-positive (Staphylococcus aureus ATCC 6538) and Gramnegative bacteria (Pseudomonas aeruginosa ATCC 9027).
Interest in sucrose derivatives has increased in recent years due to their different applications in various industrial sectors (pharmaceutical, bioengineering, chemistry, agriculture and food). Sucrose is the most abundant naturally occurring disaccharide, obtained in a high degree of purity and economical, which by means of organic reactions allows to synthesize a series of higher added value compounds. Sucrose esters (SEs) are one of the possibilities of derivatives of this carbohydrate, have applications as emulsifiers, microbiological controllers, anti-inflammatories, antioxidants, among others. However, the low stability in acidic and thermal conditions and the sucrose functional richness lead to the search for new methods of synthesis of sucroderivatives by selective reactions where the degree of esterification (specifically monoacylation) and the acylation position in the same process are controlled. On the other hand, picolinic, nicotinic and isonicotinic acids (pyridinic acids) have been studied as antimicrobial agents, anticancer agents, dietary supplements, among others, which make them chemical compounds of biological and pharmaceutical interest still little explored as carbohydrate substituents. In this study, pyridine esters of sucrose were synthesized by transesterification reaction by homogeneous basic catalysis (sodium methoxide) and heterogeneous catalysis (mixed metal oxides derived from hydrotalcites) assisted by acoustic cavitation at 20 kHz. Once the best catalyst was determined in the synthesis of SEs, a 32 x 2 experimental design was used to identify the influence of factors such as: i) irradiation time with ultrasound, ii) molar ratio of starting reagents and iii) temperature of the system, evaluated by determining the consumption of the starting methyl ester. Consumption ≥ 75% and high percentages of monosubstituted SEs (≥ 85%) were obtained. The regioisomers of greatest abundance of each pyridine SEs are isolated, characterized and proved their properties as microbial inhibitors in Gram-positive (Staphylococcus aureus ATCC 6538) and Gramnegative bacteria (Pseudomonas aeruginosa ATCC 9027).
Descrição
Palavras-chave
Ésteres de sacarose, Ácidos piridínicos, Atividade antimicrobiana, Cavitação acústica, Sucrose esters, Pyridinic acid, Antimicrobial activity, Acoustic cavitation