Electrochemical and Spectrophotometric Methods for Polyphenol and Ascorbic Acid Determination in Fruit and Vegetable Extracts

Pozadina istraživanja. Svježe rezano voće i povrće smatra se dobrim izvorom antioksidacijskih spojeva. Međutim, njihova trajnost je ograničena zbog smanjenja kakvoće proizvoda, nutritivnih vrijednosti i sigurnosti. Stoga su u posljednje vrijeme razvijeni različiti postupci obrade i čuvanja hrane te određivanja antioksidacijskih spojeva koji nakon konzumacije imaju višestruko povoljan učinak na zdravlje. Svrha je ovoga rada bila usporediti rezultate analize sastava polifenola i askorbinske kiseline u ekstraktima voća (patlidžan), jestivog korijenja (mrkva) i lišća (radič, zelena salata i blitva) dobivene elektrokemijskom i spektrofotometrijskom metodom, te procijeniti njihovu mogućnost detekcije neznatne promjene sastava antioksidacijskih spojeva u ekstraktu ploda patlidžana izloženom UV-C svjetlosti različitog intenziteta. Eksperimentalni pristup. Polifenolni spojevi i askorbinska kiselina određeni su elektrokemijskom i spektrofotometrijskom metodom. Za određivanje polifenolnih spojeva elektrokemijskom metodom korišten je enzimski biosenzor, a za određivanje askorbinske kiseline nanokompozitni biosenzor. Za spektrofotometrijska mjerenja korištene su sljedeće metode: Folin-Ciocalteu i metoda koju su razvili Kampfenkel i suradnici. Rezultati i zaključci. Rezultati dobiveni pomoću ove dvije, različite metode usporedivi su i u skladu s očekivanjima. Obje metode mogu poslužiti za određivanje udjela askorbinske kiseline i polifenola u ekstraktima voća i povrća. Osim toga, obje su metode detektirale promjenu u koncentraciji analita u uzorcima izloženim različitom intenzitetu UV-C zraka i vremenu skladištenja. Naposljetku, opaženo je da antioksidacijski kapacitet ovisi o vrsti hrane, postupku obrade te vremenu skladištenja. Novina i znanstveni doprinos. Obje su metode prikladne za kvantifikaciju analita; međutim, elektrokemijski su senzori bili specifičniji i selektivniji, mogli su se primijeniti na različite uzorke voća i povrća, te su pomoću njih dobiveni precizniji rezultati u kraćem vremenskom razdoblju i manjem volumenu uzorka, što smanjuje troškove radi manje potrošnje reagensa.Research background. Fresh-cut fruits and vegetables are considered sources of antioxidant compounds. However, their shelf life is limited due to nutritional, quality and safety deterioration. Therefore, in recent decades, various methods have been reported for food processing and preservation, as well as for the determination of antioxidant compounds, due to their many benefits when consumed. The aim of the present work is to compare the performance of electrochemical and spectrophotometric methods in the analysis of the content of polyphenolic compounds and ascorbic acid in extracts from fruits (eggplant), edible roots (carrot) and leaves (rocket, lettuce and chard), and evaluate their capability to detect small changes in the antioxidant content in the eggplant extracts previously irradiated with different UV-C light intensities. Experimental approach. Polyphenolic compounds and ascorbic acid were determined by electrochemical and spectrophotometric methods. An enzymatic biosensor and a nanocomposite sensor were used for polyphenolic compounds and ascorbic acid, respectively, in electrochemical measurements, while Folin-Ciocalteu and Kampfenkel methods were used for spectrophotometric measurements. Results and conclusion. Results obtained through the different methodologies were comparable and consistent with each other. Both methods allowed determining the content of ascorbic acid and polyphenolic compounds in the fruit and vegetable extracts. Moreover, both techniques enable the detection of the analyte concentration changes in samples exposed to different UV-C intensities and storage days. Finally, it was observed that the antioxidant capacity depends on the type of food, treatment and storage period. Novelty and scientific contribution. Both methodologies were suitable for the quantification of analytes; however, the electrochemical sensors provided higher specificity and selectivity, applicable to different fruit and vegetable matrices, obtaining results with higher precision, in shorter time and with a smaller sample volume, minimizing the economic costs because of the lower consumption of reagents

Influence of Plant Diversity on the Numerical Response of Eriopis connexa (Coleoptera: Coccinellidae) to Changes in Cereal Aphid Density in Wheat Crops

Cereal aphids cause economic injury to wheat crops. In Argentina, Eriopis connexa is an indigenous ladybird. In the present study, the numerical response of E. connexa to changes in aphid density on wheat crops with high and low plant diversity was investigated. The study was carried out in Balcarce, Buenos Aires, Argentina, from September to December 2007 and 2008, on two wheat crops with either a higher plant diversity (HPD) with refuge strips or a lower plant diversity (LPD) without refuge strips. Crops were sampled every week and the abundance of aphids and E. connexa was recorded. The dominant aphid species were Schizaphis graminum, Metopolophium dirhodum, and Sitobion avenae. Eriopis connexa showed a linear increase in the numerical response to an increase in aphid density, which varied in space and time. The abundance of E. connexa increased in relation to the crop development and aphid population and was higher in the HPD than in the LPD system. This predator increased its reproductive numerical response only in 2008, with a significant liner response in the HPD system. This suggests that the potential of E. connexa as a predator of cereal aphids also increases directly in proportion to landscape vegetal diversity

Evolution over Time of Ventilatory Management and Outcome of Patients with Neurologic Disease∗

OBJECTIVES: To describe the changes in ventilator management over time in patients with neurologic disease at ICU admission and to estimate factors associated with 28-day hospital mortality. DESIGN: Secondary analysis of three prospective, observational, multicenter studies. SETTING: Cohort studies conducted in 2004, 2010, and 2016. PATIENTS: Adult patients who received mechanical ventilation for more than 12 hours. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among the 20,929 patients enrolled, we included 4,152 (20%) mechanically ventilated patients due to different neurologic diseases. Hemorrhagic stroke and brain trauma were the most common pathologies associated with the need for mechanical ventilation. Although volume-cycled ventilation remained the preferred ventilation mode, there was a significant (p < 0.001) increment in the use of pressure support ventilation. The proportion of patients receiving a protective lung ventilation strategy was increased over time: 47% in 2004, 63% in 2010, and 65% in 2016 (p < 0.001), as well as the duration of protective ventilation strategies: 406 days per 1,000 mechanical ventilation days in 2004, 523 days per 1,000 mechanical ventilation days in 2010, and 585 days per 1,000 mechanical ventilation days in 2016 (p < 0.001). There were no differences in the length of stay in the ICU, mortality in the ICU, and mortality in hospital from 2004 to 2016. Independent risk factors for 28-day mortality were age greater than 75 years, Simplified Acute Physiology Score II greater than 50, the occurrence of organ dysfunction within first 48 hours after brain injury, and specific neurologic diseases such as hemorrhagic stroke, ischemic stroke, and brain trauma. CONCLUSIONS: More lung-protective ventilatory strategies have been implemented over years in neurologic patients with no effect on pulmonary complications or on survival. We found several prognostic factors on mortality such as advanced age, the severity of the disease, organ dysfunctions, and the etiology of neurologic disease