Flavonoids are metabolites occurring in all plant tissues and present different biological activities. They occur in a mixture of similar polarity with laborious separation and purification processes, usually furnishing low yields. Semi-preparative chromatographic methods are universally employed procedures for their isolation. This paper discusses the state-of-the-art in new non-chromatographic techniques for the separation and purification of flavonoids. In the last decades, novel methods for flavonoids purification have been developed to decrease time extraction, reduction of costs, and organic solvent. Herein, we present the state-of-the-art development of ionic liquids, eutectic solvents, chelating agents, and molecular imprinted polymers in greener extractions, enrichments, and the purification of flavonoids. As the main advantage, these proceedings permitted good yields of bioactive flavonoids and biflavonoids, and they are improved when ultrasound, microwave, and mechanical extractors are used in the extraction step. Nevertheless, most of these techniques are not specific to a single molecule’s purification, except MIPs mainly used for analytical purposes. These examples indicate that the development of efficient and straightforward methods for the obtention of different bioactive flavonoids is still incipient but with potential for discovering specific and greener procedures for isolating the target compounds in good yields.

Resumo São conhecidos vários métodos de extração que podem ser aplicados para a quantificação de compostos fenólicos e, portanto, cabe ao pesquisador aperfeiçoar o processo que melhor se aplica à amostra em questão. Diferentes solventes de extração (extração líquido-líquido) foram comparados a fim de avaliar a sua eficácia para a análise de fenóis totais em extrato de polpa de jambolão ( Syzygium cumini Lamark), usando metodologia convencional de Folin-Ciocalteau. Três DCCRs (Delineamento composto central rotacional) foram realizados para avaliar os fatores que influenciam as condições de processo de extração. As variáveis estudadas foram a concentração de solvente (etanol e metanol, diluído em água) e o tempo de mistura no processo de extração de compostos. Das condições estudadas, foi demonstrado que um solvente de extração 60% de etanol em água, com um tempo de mistura de 10 minutos, além de extrair uma maior concentração de compostos fenólicos, apresenta grande vantagem de custo-benefício, uma vez que o etanol é mais barato e menos tóxico do que o metanol.

Abstract There are various known extraction methods that can be applied to the quantification of phenolic compounds, and thus it is up to the researcher to perfect the process that best applies to the sample in question. Different extraction solvents (liquid-liquid extraction) were compared in order to assess their effectiveness for the analysis of total phenols in jambolan ( Syzygium cumini Lamark) pulp extract using the conventional Folin-Ciocalteau methodology. Three CCRDs (Central Composite Rotational Designs) were carried out to evaluate the factors influencing the extraction process conditions. The variables studied were the solvent concentration (ethanol and methanol, diluted in water) and the mixing time in the compound extraction process. Of the conditions studied, it was shown that a 60% ethanol in water extraction solvent with a mixing time of 10 minutes, in addition to extracting a greater concentration of phenolic compounds, showed the greatest cost benefit advantage, since ethanol is cheaper and less toxic than methanol.

Propolis is a complex mixture composed by salivary secretions of bees and a resinous and balsamic material collected by them from different part of plants. This material is well employed by people due its antimicrobial, antioxidant, anti-inflammatory, antiviral properties beside others. However, the chemical composition varies according the habitat and season. This work describes the identification of saturated hydrocarbons, methyl cinnamate, sitosterol cinnamate and ananixanthone isolated from the brown propolis produced in Bahia, Brazil, classified as Propolis Type 6. Besides, antioxidant activities and cytotoxicity of the extracts were evaluated by the DPPH quenching and Brine Shrimp Test. The extracts showed weak antioxidant activities and high cytotoxicity, especially the methanol and chloroformic extracts.

This paper describes the chemical composition and acetylcholinesterase inhibition of an active chromatographic fraction of the EtOAc extract of Citrus limon leaves. The composition of the active fraction presented a mixture of two coumarins, 5,8-dimethoxy-psoralen and 5,7- dimethoxycoumarin, identified by ¹H and ¹³C NMR data analysis, including DEPT, COSY, HMBC and HSQC experiments. It was also demonstrated that this mixture presents qualitative and quantitative AChE inhibition. In vitro studies indicated a CE50 value of 340 µg/mL with 95% of confidence. In vivo studies (10 and 25 mg/kg) revealed inhibition of 30.09 and 30.06% of AChE activity in relation to neostigmine, respectively.

This work describes the isolation of an active flavonoid fraction and identification of isorhamnetin 3-O-β-D-(6''-acetyl)-galactopyranoside from flowers of B. perennis, and also the evaluation of anticholinesterase (AChE) activity of ethanolic extract from flowers (EEF) and the active fraction. The chemical structure of the flavonoid was defined on the basis of spectroscopic ¹H NMR, IR and UV data. EEF or flavonoid reduces AChE activity in vivo, while flavonoid also reduces AChE activity in vitro, showing a value of 1.49 mM for 50% inhibitory concentration (IC50), suggesting potential use as an insecticide or in the treatment of neurodegenerative diseases such as Alzheimer's disease.