In vitro liberation of carotenoids from spinach and Asia salads after different domestic kitchen procedures

Arid/semi-arid flora as a treasure trove of bioactives and bioenergy: the case for underutilized desert legumes towards environmental sustainability

As the spectre of climate change gains in strength with each passing moment, many of our mundane food crops like rice face the heat, leading to uncertain yields and unforeseen disease outbreaks. Subsequently, mankind is forced to look for alternative food choices that should primarily come from indigenous plants that are less demanding in terms of usage of water and application of chemical-based fertilizers/pesticides. There are plants growing in the wild in the arid and semi-arid zones of Rajasthan, India, that can come to the rescue, with an added potential for development into valuable functional foods-i.e., not only as source of carbohydrates, proteins, and micro-nutrients but also that of health benefiting nutraceuticals (like antioxidant flavonoids) and relevant enzymes. The other parts (non-edible) of these plants have often also been traditionally validated via diverse ethnomedicinal practices; these could also be useful bioenergy sources. Keeping in mind the broader aim of looking at future functional foods that are also required to be environmentally sustainable, the current report: (a) reviews the extant literature on underutilized legumes from arid/semi-arid zones, (b) discusses current status with respect to biological activities present therein, and (c) suggests pertinent research questions and solution paths in the domains of bioactives, bioenergy, and sustainable environment.

Enzymatic acylation improves the stability and bioactivity of lutein: Protective effects of acylated lutein derivatives on L-O2 cells upon H2O2-induced oxidative stress

The instability of lutein has limited its wide application especially in the food industry. In this study, enzymatic acylation of lutein with divinyl adipate was investigated. Three new acylated lutein derivatives, lutein-3-O-adipate (compound 1), lutein-3'-O-adipate (compound 2) and lutein-di-adipate (compound 3), were identified and their stabilities and bioactivates were evaluated. Notably, compounds 1-3 showed better thermal, light stability and stronger scavenging capacity to ABTS radical cation (ABTS⁺) and hydroxyl radical (OH). Most importantly, these acylated lutein derivatives exhibited excellent protective effects on L-O2 cells upon hydrogen peroxide (H₂O₂)-induced oxidative stress. In particular, the acylated lutein derivative termed compound 3 prevented cellular oxidative stress via restraining the overproduction of reactive oxygen species (ROS), thereby increasing related antioxidant enzymes activity and inhibiting apoptosis by mitochondria pathway. Our research provides important insights into the application of acylated lutein derivatives in food, cosmetic, and pharmaceutical products.

Oxidative stability of lutein on exposure to varied extrinsic factors

Pre-processing treatments performed on lutein sources can cause it to degrade, generating superfluous metabolites and lowering lutein's bioactivity. However, evidences suggesting extent of reduction in functional stability of lutein on exposure to such treatment conditions are nil. This study is first of its kind, where we attempted to gain clarity on the extent of degradation caused by the changes in temperature (40-100 °C), pH (2-8) and duration of such treatments. Increase (3.9 folds) in lutein loss within an hour at 40 °C occurred when pH was lowered from 8 to 2. Increase (1.7 folds) in lutein loss at neutral pH and 40 °C occurred when duration of exposure was increased from 1 to 4 h. Besides, lutein loss significantly increased on rising the temperature by every 10 °C. The functional stability of lutein in relation to its degradation was also studied by monitoring its radical scavenging activity. While lutein is highly unstable, lutein structure and its respective bioactivity can be significantly (p < 0.05) retained (< 12.44% and > 54.87% respectively) by maintaining the operating conditions at higher pH (7-8) and lower temperatures (40-50 °C) for a short period of time (< 1 h).

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05430-3.

Effect of Green Synthesized Iron Oxide Nanoparticles Using Spinach Extract on Triton X-100-Induced Atherosclerosis in Rats

The effect of iron oxide nanoparticles (FeONPs) synthesized using Spinacia oleracea leaf extract on Triton X-100-induced atherosclerosis in white Wistar rats was determined. FeONPs were characterized to determine their size, structure, composition, and shape. In vitro antioxidant activity of FeONPs against 2, 2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) was determined. Atherosclerosis was induced by intraperitoneal administration of 5% Triton X-100 (100 mg/kg body weight) for 14 days. Group 1 received standard rat chow and water. Group 2 received 100 mg/kg body weight of Triton X-100 and a standard diet. Group 3 received 100 mg/kg body weight of Triton X-100 followed by 20 mg/kg body weight of atorvastatin for 21 days. Groups 4, 5, and 6 received 100 mg/kg body weight Triton X-100 was followed by variable concentrations of 100, 300, and 500 µg/kg body weight FeONPs, respectively, for 21 days. Blood samples were analyzed for lipid, liver, antioxidant, and cardiovascular markers. Histopathology of the heart was also examined. Characterization revealed the amorphous nature, functional groups, and clustered topography of FeONPs. An upregulated antioxidant activity of FeONPs was observed in a dose-dependent manner. Administration of Triton X-100 showed elevated levels of lipid biomarkers except for high-density lipoprotein (HDL), which decreased in group 2 in comparison to group 1. Liver, antioxidant, and cardiovascular biomarkers all significantly increased. The structural alteration was observed in the heart tissue following histopathology examination. Administration of FeONPs significantly decreased all biomarkers and increased the level of HDL. Also, tissue architecture was restored. Our findings demonstrated that FeONPs were effective in ameliorating Triton X-100-induced atherosclerosis in rats.

Exploration of suitable in vitro simulated digestion model for lipid oxidation of flaxseed oil emulsion during digestion

BACKGROUND

The INFOGEST model is a standardized general in vitro digestion study, but it cannot accurately simulate the fatty acid release process of lipids in the stomach and small intestine. In this study, the internationally universal INFOGEST 2019 was used as the basic model and flaxseed oil emulsion was used as the research object. In various improvement models, the effect of fatty acid release rate on the oxidation stability of flaxseed oil was assessed by adding rabbit stomach extract and changing the order of bile salts addition.

RESULTS

With the presence of rabbit gastric extract, flaxseed oil emulsion flocculation and coalescence in stomach were reduced, and the absolute value of ζ-potential increased. Moreover, the release rate of fatty acids in the small intestine increased by 12.14%. The amount of lipid oxidation product (i.e. hexanal) in the gastric and intestinal phases increased by 0.08 ppb. In addition, the fatty acid release rate in the small intestine phase increased by 5.85% and the hexanal content increased by 0.011 ppb in the digestion model of adding bile salts before adjusting the pH in the small intestine phase compared with the model of adjusting the pH first and then adding bile salts.

CONCLUSION

The results obtained from this study will contribute to finding the most suitable static digestion model for simulating digestion and oxidation of lipid during lipid gastrointestinal digestion. © 2022 Society of Chemical Industry.

Loss or Gain of Lipophilic Bioactive Compounds in Vegetables after Domestic Cooking? Effect of Steaming and Boiling

Lipophilic antioxidants are essential components, which have been pointed as bioactive beneficial for human health. This study aimed at evaluating the effect of domestic cooking (boiling, steaming) on the main carotenoids (lutein and β-carotene) and tocols in four different green leafy vegetables: Sonchus asper L. Hill, Sonchus oleraceus L., Spinacia oleracea L. and Cichorium intybus L. The total content of the analyzed compounds was determined following the method of alkaline hydrolysis of the matrix and solvent extraction. The leaching of soluble solids after domestic cooking was found to determine a gain in the investigated bioactive compounds in the cooked vegetables, so to cause an apparent content increase in all leafy vegetables, when expressed as mg/100 g dry matter. Considering solid losses, all lipophilic compounds were not affected by boiling; on the contrary, steaming slightly significantly decreased the contents of lutein and β-carotene (on average 20 and 15%, respectively).

Addition of either gastric lipase or cholesterol esterase to improve both β-cryptoxanthin ester hydrolysis and micellarization during in vitro digestion of fruit pulps

Using the INFOGEST in vitro digestion protocol adapted to carotenoids, the impact of additional rabbit gastric lipase (RGL) on the hydrolysis extent of β-cryptoxanthin esters was evaluated for the first time, and compared with the addition of porcine cholesterol esterase (CEL). Both the modifications increased the hydrolysis of (all-E)-β-cryptoxanthin esters from mandarin and peach pulps, although the outcomes were different. Addition of RGL consistently increased the average hydrolysis extent from 55.2% to 59.5% in mandarin pulp and from 22.7% to 48.8% in peach pulp (p < 0.05). The addition of CEL produced lower hydrolysis extents, i.e., 58.5% in mandarin (not statistically significant) and 28.4% in peach (p < 0.05), compared to those obtained with RGL. The hydrolysis extent positively correlated with the carotenoid ester concentration in both matrices. Bioaccessibility values were higher in mandarin pulp (range 32-34%) compared to those in peach pulp (range 16-21%), and were associated with the hydrolysis extent of the carotenoid esters during digestion. Addition of RGL and CEL produced no significant (p < 0.05) effect on the overall carotenoid bioaccessibility values of mandarin, while positively affected those in peach. Altogether these results corroborate that the hydrolysis extent of xanthophyll esters limits bioaccessibility. Additionally, hydrophobicity of the carotenoid inversely correlates with micellarization, as free (all-E)-xanthophylls micellarized in a higher extent compared to (all-E)-β-carotene and xanthophyll esters. The new information of our results is that the addition of rabbit gastric lipase substantially contributes to the hydrolysis of β-cryptoxanthin esters from fruit pulps, and consequently, to increase carotenoid bioaccessibility, being even more effective than CEL.

Bile amount affects both the degree of micellarization and the hydrolysis extent of carotenoid esters during in vitro digestion

Carotenoid esters are present in considerable amounts in most fruits, such as in citrus. Although the bioavailability of carotenoid esters is similar or even higher compared to that of free carotenoids, these molecules are generally detected only in the free form in human plasma, suggesting that hydrolysis of carotenoid esters occurs in vivo. However, the available in vitro digestion methods were not able to achieve satisfactory carotenoid ester hydrolysis so far. As bile salts play an essential role in the hydrolytic action of lipolytic enzymes from pancreatin, we evaluated the effect of increasing the bile extract/food ratio from 0.045 to 0.12 (g g-1) on the hydrolysis of β-cryptoxanthin esters from mandarin pulp during in vitro digestion. Additionally, considering the positive effect of lipids on carotenoid bioavailability, the impact of soybean oil addition on carotenoid ester hydrolysis was studied. Finally, bioaccessibility and recovery of 33 carotenoids were assessed by LC-DAD-MS. The hydrolysis extent of β-cryptoxanthin esters enhanced from 29% to 55% by increasing the bile extract/food ratio, but reduced respectively to 28% and 11% by the addition of 1% and 10% oil (p < 0.05). The bioaccessibility of overall carotenoids improved from 19% to 35% by increasing the bile extract/food ratio, along with that of (all-E)-β-carotene (from 19 to 31%) and total (all-E)-β-cryptoxanthin (17% to 49%). Soybean oil addition reduced carotenoid micellarization, regardless of the concentration (p < 0.05). Irrespective of the bile extract amount and oil addition, the bioaccessibility of carotenoids was inversely related to its hydrophobicity, with respect to the following ranking: free xanthophylls > carotenes ≥ xanthophyll esters. Altogether, these results indicate that increasing the bile extract amount is a simple and inexpensive option to improve carotenoid ester hydrolysis in in vitro digestion protocols. Additionally, the constant amounts of bile (and possibly enzymes) of static methods, such as INFOGEST, should be further optimized for experiments involving lipid addition in which carotenoid bioaccessibility is evaluated.

The impact of galactooligosaccharides on the bioaccessibility of sterols in a plant sterol-enriched beverage: adaptation of the harmonized INFOGEST digestion method

The effect of the addition of galactooligosaccharides (GOS) on sterol bioaccessibility in three plant sterol (PS)-enriched milk-based fruit beverages (without GOS addition (MfB) and with 2.5 g (MfB-G2) and 5.0 g (MfB-G5) GOS per 250 mL) was evaluated after micellar gastrointestinal digestion. Cholesterol bioaccessibility was very similar among beverages, though a slight significant increase (from 80% to 85%) was observed by the addition of 5.0 g GOS. The addition of GOS did not affect total PS bioaccessibility (≈37%). Based on the results obtained after micellar digestion, it has been demonstrated that these beverages could be a suitable food matrix for simultaneous enrichment with PS and GOS. The harmonized in vitro digestion model INFOGEST was applied to the MfB beverage, but the cholesterol content could not be quantified due to its contribution of bile salts. Hence, it was proposed: (i) a change in porcine bile salt concentration from 10 mM to 1.4 mM (in order to compare with micellar digestion); or (ii) a change of bile salt origin (bovine instead of porcine), maintaining physiological concentration (10 mM, INFOGEST condition). Both options allowed cholesterol quantification, with bioaccessibilities of 62% (reduction of bile salts) and 38% (replacement of the bile salt source), whereas plant sterol bioaccessibilities were 22% and 14%, respectively. Therefore, the change of bile salt origin maintaining INFOGEST concentration is proposed as a method to evaluate sterol (cholesterol and PS) bioaccessibility in these beverages, demonstrating the need for the selection of appropriate conditions of the INFOGEST harmonized method according to the food matrix and compounds to be determined.

Effects of High Temperature Frying of Spinach Leaves in Sunflower Oil on Carotenoids, Chlorophylls, and Tocopherol Composition

Spinach is one of the highly consumed vegetable, with significant nutritional, and beneficial properties. This study revealed for the first time, the effects of high temperature frying on the carotenoids, chlorophylls, and tocopherol contents of spinach leaves. Spinach leaves were thermally processed in the sunflower oil for 15, 30, 45, and 60 min at 250°C. Reversed phase HPLC-DAD results revealed a total of eight carotenoids, four chlorophylls and α-tocopherol in the spinach leaves. Lutein, neoxanthin, violaxanthin, and β-carotene-5,6-epoxide were the major carotenoids, while chlorophyll a and b' were present in higher amounts. Frying of spinach leaves increased significantly the amount of α-tocopherol, β-carotene-5,6-epoxide, luteoxanthin, lutein, and its Z-isomers and chlorophyll b' isomer. There was significant decrease in the amounts of neoxanthin, violaxanthin, chlorophyll b, b' and chlorophyll a with increase of frying time. The increase of frying time increased the total phenolic contents in spinach leaves and fried sunflower oil samples. Chemical characteristics such as peroxide values, free fatty acids, conjugated dienes, conjugated trienes, and radical scavenging activity were significantly affected by frying, while spinach leaves increased the stability of the frying oil. This study can be used to improve the quality of fried vegetable leaves or their products at high temperature frying in food industries for increasing consumer acceptability.

Optimized, Fast-Throughput UHPLC-DAD Based Method for Carotenoid Quantification in Spinach, Serum, Chylomicrons, and Feces

An improved UHPLC-DAD-based method was developed and validated for quantification of major carotenoids present in spinach, serum, chylomicrons, and feces. Separation was achieved with gradient elution within 12.5 min for six dietary carotenoids and the internal standard, echinenone. The proposed method provides, for all standard components, resolution > 1.1, linearity covering the target range (R > 0.99), LOQ < 0.035 mg/L, and intraday and interday RSDs < 2 and 10%, respectively. Suitability of the method was tested on biological matrices. Method precision (RSD%) for carotenoid quantification in serum, chylomicrons, and feces was below 10% for intra- and interday analysis, except for lycopene. Method accuracy was consistent with mean recoveries ranging from 78.8 to 96.9% and from 57.2 to 96.9% for all carotenoids, except for lycopene, in serum and feces, respectively. Additionally, an interlaboratory validation study on spinach at two institutions showed no significant differences in lutein or β-carotene content, when evaluated on four occasions.