Identificação de pigmentos naturais de espécies vegetais utilizando-se cromatografia em papel

The use of natural dyes to demonstrate principles of paper chromatography is proposed. Extraction of the coloring compounds were performed in order to obtain the aglycone form of the anthocyanins present in the crude extracts. Separations were carried out on chromatographic paper with BAW (butanol/acetic acid/water) as mobile phase and the results compared with literature data. The crude extracts were obtained from Tibouchina granulosa, Rododhendron simsii, Impatiens walleriana flowers which are wildely found in Brazil and Phaseolus vulgaris L. grains skin which is the principal ingredient of the world famous "feijoada". Such species were chosen in order to attract the students attention since they are present in their quotidian, in agreement with the new proposals for Brazilian education.

Análise de imagem em química analítica: empregando metodologias simples e didáticas para entender e prevenir o escurecimento de tecidos vegetais

A simple and didactic experiment was developed for image monitoring of the browning of fruit tissues caused by the enzyme polyphenol oxidase. The procedure, easy and inexpensive, is a valuable tool to teach and demonstrate the redox reaction between the enzyme and the natural polyphenols. To obtain the browning percentage for apple, pear and banana, digital photographs were employed, and the images were analyzed by means of Monte Carlo methods and digital analysis programs. The effects of several experimental conditions were studied, such as pH, light, temperature and the presence of oxygen or anti-oxidants. It was observed that each fruit presented a different condition that better minimized the oxidation process. The absence of oxygen and the application of a bissulphite solution were sufficient to keep the quality of all fruits tested.

Lipases de látex vegetais: propriedades e aplicações industriais

Biocatalysts have innumerous advantages with respect to classical chemical processes, such as high specificity. Lipases (EC 3.1.1.3) are biocatalysts with large application in synthesis and hydrolysis reactions of triacylglycerols. The search for new sources of lipases has been intensified in the last years due to the high cost of microbial and animal lipases, wich restricts their use on an industrial scale. Lipases obtained from the latex of Carica papaya, Carica pentagona, Euphorbia characias, E. wulfenii, known for their proteolytic properties, are a good alternative source. In this review, we describe the well-known sources of vegetal lipases extracted from the latex and present some of their industrial applications.

Transesterificação de óleos vegetais: caracterização por cromatografia em camada delgada e densidade

We studied the transesterification of two vegetable oils: soybean and waste frying oil. The main problem of transesterification is related to the measurement of the ethyl ester content. In this work we used a quick analytical method for assessing the ethyl ester fraction of the purified fuel-grade transesterification products by applying a simple correlation with density. If the ester content is higher than 85% by weight the correlation allows the determination by a single density measurement. This method is suitable for control and determines the ethyl ester quickly and simply.

Estudo comparativo de técnicas de screening para avaliação da atividade anti-bacteriana de extratos brutos de espécies vegetais e de substâncias puras

In this work, the effectiveness of four screening techniques (three techniques of the diffusion method and one microdilution broth method) were compared. Evaluated were the ethanolic and dichloromethanic extracts of Miconia rubiginosa (Melastomataceae) against six standard bacteria (ATCC). The results showed statistical disagreement among the three diffusion techniques. Among the diffusion techniques, the well technique displayed the best result. However the microdilution broth method demonstrated to be the most adequate method to evaluate the antibacterial activity of plant crude extracts and pure compounds when compared to the other methodologies.

Otimização de método para determinação de flavonóis e flavonas em frutas por cromatografia líquida de alta eficiência utilizando delineamento estatístico e análise de superfície de resposta

This work optimized the HPLC conditions for the simultaneous determination of luteolin, apigenin, myricetin, quercetin and kaempferol in aglycone form, as well defined the best conditions for hydrolysis/extraction of these flavonoids in fruits, using the statistical central composite design and response surface analysis. A reverse phase method was developed using a gradient of methanol/water acidified with 0.3% formic acid as mobile phase and a photodiode array detector. The samples were extracted with methanol/water (50:50 v/v) at 90 ºC. The optimum time and HCl concentration varied for the different fruits investigated, demonstrating the necessity of optimizing these conditions for each fruit analyzed. Good recovery (87.1 to 96.3%), repeatability and linearity were obtained.

Co-produção de lipase e biossurfactante em estado sólido para utilização em biorremediação de óleos vegetais e hidrocarbonetos

Recently lipases have been increasing in prominence due to its wide industrial application. The lipase production can be influenced by different variables such as the producing microorganism, carbon sources, aeration and agitation conditions, inductor type and the geometry of the reactor. Biosurfactants are composites of surface active produced by microbial cells which reduce superficial and interfacial tensions. The objective of this study was to verify the influence of different process variables in the lipase production during a fermentative process. The results showed that the concomitant production of lipases and biosurfactant was possible in different cultivation conditions.

Determinação eletroquímica da capacidade antioxidante de sucos de frutas industrializados usando o CRAC assay

Fruits juices are natural sources of several compounds that present antioxidant action. Together with the fruits, they contribute with almost 40% of the antioxidant capacity in a healthy diet avoiding and preventing diseases deriving from oxidative stress. The present study determined the antioxidant capacity of seven samples of industrialized fruits juices applying CRAC (Ceric Reducing/Antioxidant Capacity) assay, a new electrochemistry assay that evaluates, by means of chronoamperometric measurements, the ability of a sample in reducing species Ce4+ in acid media. At the end of the assay was obtained the following classification: cashew > guava > grape > mango > apple > orange > passion fruit.

Fontes vegetais naturais de antioxidantes

Growing knowledge on the health-promoting impact of antioxidants in everyday foods, combined with the assumption that a number of common synthetic preservatives may have hazardous side effects has led to increased investigations in the field of natural antioxidants, principally those found in plants. Food industries normally discard plant residues that could benefit the human health and diminish undesirable environmental impact. Once estimated the content of antioxidants in these residues, advantageous economical and social alternatives to the discard are possible, for example, their use for preparation of nutraceuticals to be offered to low-income populations. We present here a broad, although not complete, account of the continuously growing knowledge on the antioxidant capacity of whole fruits, seeds and peels, cereals, vegetal oils and aromatic plants, at several physical forms, as well as a description of the usual methods for evaluating their antioxidant capacity and examples of agroindustrial processes that could be harnessed for the production of antioxidant supplement food, along with research perspectives in the area.

Validação de metodologia para a determinação simultânea dos antioxidantes sintéticos em óleos vegetais, margarinas e gorduras hidrogenadas por CLAE/UV

The use of antioxidants either to prevent or retard food's lipids oxidation was approved after inquires that verified their security within a daily intake limit. In this study, the methodology was developed and validated for the analysis of synthetic antioxidants: propylgallate (PG), tert-butylhydroquinone (TBHQ), butylhydroxyanisole (BHA), octylgallate (OG) and butylhydroxytoluene (BHT) in vegetables oils, margarine and hydrogenated fats by high performance liquid chromatographic. The methodology revealed itself efficient, with recovery rates above 90% for all antioxidant substances, besides good linearity in concentration range of 40-240 mg kg-1 (r = 0,999), repeatability with CV < 3,7% and limit of quantification 16.55, 10.32, 1.40, 3.76 and 9.30 mg/kg for BHT, BHA, PG, OG and TBHQ, respectively.

Tocoferois e tocotrienois em óleos vegetais e ovos

The distribution and content of vitamin E isomers was investigated in vegetable oils and raw and cooked egg yolk in commercial restaurants. The analysis of the eight vitamin E isomers was carried out by High Performance Liquid Chromatography (HPLC) with fluorescence detection. The tocopherol and tocotrienol composition of foods varied considerably. Tocopherols were detected in greater quantity and frequency. The α-tocopherol predominated in egg yolks and olive oil while γ-tocopherol was found in high quantities in soybean and canola oils. Cooking did not cause major losses for most of the vitamin E isomers in egg yolks.

Determinación de vitamina C, compuestos fenólicos totales y actividad antioxidante de frutas de guayaba (Psidium guajava L.) cultivadas en Colombia

Some physicochemical parameters, vitamin C, total phenolic compounds and antioxidant activity (AA) measured by ABTS, FRAP and DPPH methods were determinated in four different varieties of ripe guava produced in Colombia. Samples were statistically similar in their titratable acidity. Soluble solids were statistically similar and higher in "Pear", "Pink Regional", and "White Regional", but lower in "Apple" guavas. Vitamin C was statistically lower in "Pear" guava. Phenolics, ABTS-, FRAP-, and DPPH-AA were statistically lower in "Apple" guava if compared in wet basis. "Pink Regional" and "White Regional" contained the highest levels in vitamin C, phenolics and antioxidant activity.

Determinação de enxofre em amostras vegetais por oxidação via seca em meio alcalino com detecção espectrofométrica

The sulphur take an essential role in plants and it is one of the main nutrients in several metabolic processes. The dry ash oxidation, using alkaline oxidizers agent, is the simplest and most economical form for the oxidation of Organic S to sulfate in plants. The objective of this work is to propose a method for sulfur determination in plants samples using dry ash oxidation and agent oxidizers alkaline. The quantification of S-SO4(2-) in samples was accomplished by turbidimetric method. The results demonstrated that the proposed method for oxidation alkaline was appropriate.

Experimento didático de quimiometria para análise exploratória de óleos vegetais comestíveis por espectroscopia no infravermelho médio e análise de componentes principais: um tutorial, parte I

This manuscript aims to show the basic concepts and practical application of Principal Component Analysis (PCA) as a tutorial, using Matlab or Octave computing environment for beginners, undergraduate and graduate students. As a practical example it is shown the exploratory analysis of edible vegetable oils by mid infrared spectroscopy.

Quantificação dos isômeros ácido L-ascórbico e ácido D-iso-ascórbico em geleias de frutas por cromatografia líquida de alta eficiência

Ascorbic acid has important nutritional characteristics such as high antioxidant potential, preventing diverse damage and diseases in the tissues and the process of aging. Different isomeric forms of the ascorbic acid can be found in nature and each one have different potential antioxidant and different activity pro-vitamin C. This work examined a method to detect and quantify the isomers L-ascorbic acid (LAA) and D-iso-ascorbic acid (DIAA) in jelly fruit. The method showed acceptable selectivity, linearity, repeatability and recovery. DIAA was not found in the analyzed samples, but LAA was found up to 605 mg in 100 g of sample.