Optimization of an Extraction Process to Obtain a Food-Grade Sulforaphane-Rich Extract from Broccoli (Brassica oleracea var. italica)

Sulforaphane (SFN) is a powerful health-promoting compound found in broccoli in the form of its inactive precursor, glucoraphanin (GFN). SFN formation occurs through the enzymatic hydrolysis of glucoraphanin by myrosinase under specific chemical conditions. Its incorporation in food formulations has been hindered by the thermal instability of SFN and low concentration in Brassicaceae. Then, extracting SFN from broccoli at a temperature below 40 °C appears as an option to recover and stabilize SFN, aiming at delivering it as a nutraceutical. We studied an eco-friendly extraction process to obtain an SFN-rich extract from broccoli. The effect of the broccoli mass/solvent ratio, ethanol concentration in the extractant solution, and extraction time on the recovery of SFN, GFN, phenolic compounds, and antioxidant activity were studied through a Box–Behnken design. The regression models explained more than 70% of the variability in the responses, adequately representing the system. The experimental factors differently affected the bioactive compound recovery and antioxidant activity of the extracts. The extraction conditions that allowed the highest recovery of bioactive compounds and antioxidant activity were identified and experimentally validated. The results may provide the basis for the design of a process to produce a sulforaphane-rich food supplement or nutraceutical by using a GRAS extractant.

Effects of FeEDDS and EDDS on Peat-based Substrate pH and Cu, Fe, Mn, and Zn Solubility

Common chelating agents used in horticultural fertilizers like ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA) are not readily biodegradable and may persist in the environment, maintaining the capacity to solubilize heavy metals. For this reason, biodegradable chelating agents like ethylenediaminedisuccinic acid (EDDS) are being evaluated for use in horticultural crop production. Therefore, the objectives of the study were to determine the effects of FeEDDS and EDDS on substrate pH and copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) solubility in peat-based substrate compared with various Fe and chelate-ligand sources. Extractions were performed using the 1:2 by volume substrate analysis method with an incubation period of 24 hours. The control was distilled deionized water extractions. Iron-source (FS) extractants consisted of 1 mg·L−1 Fe solutions derived from FeEDDS, FeEDTA, FeDTPA, FeEDDHA, and FeSO4. Iron-source extractant solution pH ranged from 7.1 (FeEDDS) to 5.4 (FeSO4). The extract pH for all Fe-source treatments was similar at pH 6.7, demonstrating the buffering capacity of the peat-based substrate. Iron recovery rates for FS treatments were determined after subtracting Fe that was freely extracted with distilled-deionized water: FeSO4 (13%), FeEDDHA (68%), FeEDDS (73%), FeEDTA (102%), and FeDTPA (121%). Iron-source treatments were not different for Mn, averaging 0.03 mg·L−1, and Cu (0.04 mg·L−1) and Zn (0.24 mg·L−1) were greatest in the FeEDDS treatment. Chelate-ligand (CL) extractants consisted of 5 mm solutions of EDDS, EDTA, and DTPA. Chelate-ligand extractant solution pH ranged from 9.7 (EDDS) to 2.3 (DTPA), and extract solution pH ranged from 7.2 (EDDS) to 4.7 (DTPA). Extractant solutions of EDDS and DTPA resulted in the lowest and highest levels of Cu (0.06 and 0.14 mg·L−1, respectively) and Fe (4.3 and 13.1 mg·L−1, respectively) in extract solutions. Overall, these results suggest that there are no negative implications for the use of FeEDDS with peat-based substrate in terms of horticultural crop production based on substrate Fe solubility, which was not different from FeEDTA.

Organic acid mediated nutrient extraction efficiency in three calcareous soils

This study was conducted to evaluate the effects of organic acids on the concentrations of metals and anions in soil solution. Three soils with contrasting CaCO3 contents were extracted with organic acid solutions (citrate and oxalate) of different concentrations for different time periods and analysed for Fe, Mn, Zn, Cu, P, and Ca. The soils showed a significant change after the addition of the organic acids to the soil. The mobilisation of metals from the solid phase was dependent on concentration and ionic form of organic acid. High concentrations of citric acid were more effective than oxalate in mobilising Ca, Fe, Mn, and Zn. Overall; oxalate was slightly more effective than citrate in mobilising P. Generally, the higher the organic acid concentration of the extractant solution, the greater was the amount of elements extracted from the soil. Citrate tended to be more effective than oxalate at mobilising elements from the soil. All pH changes were dependent on organic acid concentration.

Kinetics of K release from soils of Brazilian coffee regions: effect of organic acids

Kinetic studies on soil potassium release can contribute to a better understanding of K availability to plants. This study was conducted to evaluate K release rates from the whole soil, clay, silt, and sand fractions of B-horizon samples of a basalt-derived Oxisol and a sienite-derived Ultisol, both representative soils from coffee regions of Minas Gerais State, Brazil. Potassium was extracted from each fraction after eight different shaking time periods (0-665 h) with either 0.001 mol L-1 citrate or oxalate at a 1:10 solid:solution ratio. First-order, Elovich, zero-order, and parabolic diffusion equations were used to parameterize the time dependence of K release. For the Oxisol, the first-order equation fitted best to the experimental data of K release, with similar rates for all fractions and independent of the presence of citrate or oxalate in the extractant solution. For all studied Ultisol fractions, in which K release rates increased when extractions were performed with citrate solution, the Elovich model described K release kinetics most adequately. The highest potassium release rate of the Ultisol silt fraction was probably due to the transference of "non-exchangeable" K to the extractant solution, whereas in the Oxisol exchangeable potassium represented the main K source in all studied fractions.

A field test method for soluble (0.02 M CaCl2 extractable) aluminum in soils

A field test is described for determination of 0.02 M CaC12 extractable ('soluble') aluminium in soils. The method uses a 5 min extraction (2 min shaking followed by 3 min settling period). An aliquot of extract is then added to the metallochromic reagent chrome azurol S, CAS (amber). Aluminium reacts rapidly with CAS in hexamine buffer (pH 4.9) to form a 1 : 1 complex, Al(CAS) (purple). Intermediate colours arise in solutions where CAS is partly converted to the aluminium complex. The developed colour may be compared visually (or spectrophotometricaliy in the laboratory) with standards. Alternatively the CAS concentration may be selected to give the purple colour at a predetermined concentration of aluminium in the extractant solution, corresponding to the toxicity threshold for a specific crop and soil. CAS-reactive Al (5 min extraction) was correlated with total Al (1 h extraction; AAS) soluble in 0.02 M CaCl2, by Alt = 1.62[CAS-Al]+0.5 for soils with Alt < 60 mg kg-1 (n = 22; r2 = 0.99).

Extraction of iron with dibenzyl sulfoxide solution sorbed on silica gel

The amount of dibenzyl sulfoxide (DBSO) sorbed on silica gel from toluene solutions was measured for different silica gel hydrophobization procedures and in dependence on the initial DBSO concentration in the solution. From silica gel impregnated with DBSO solution, the sulfoxide is washed out by hydrochloric acid even if the acid has been saturated by shaking with 0.05M solution of DBSO in toluene. The effect of HCl and DBSO concentrations on the recovery of iron was investigated both for liquid-liquid extraction and for extraction with the extractant solution sorbed on silica gel. The recoveries for the two cases are equal, which implies that the ratios of the activity coefficients of the reagent and of the extracted complex for the liquid-liquid extraction and for the extraction with the extractant sorbed on hydrophobized silica gel are the same.