Development of a rapid HPLC-UV method for simultaneous quantification of protodioscin and rutin in white and green asparagus spears

Abstract: Asparagus (Asparagus officinalis L.) spears are rich in bioactive compounds such as protodioscin, a saponin, and rutin, a flavonoid. Protodioscin and rutin are routinely quantified separately, and an approach permitting simultaneous measurement would significantly improve speed of analysis. We have optimized an extraction procedure and modified a method of high-performance liquid chromatography by coupling to an ultraviolet detector to simultaneously analyze protodioscin and rutin in asparagus extracts. An acidic ethanol solvent was more efficient than methanol, acetonitrile, or water in coextraction of protodioscin and rutin. Protodioscin and rutin were detected at 210 nm, with retention times of 12.6 min and 7.9 min, respectively. The method was validated by high linear correlations between 3.13 and 1000.0 μg/mL for protodioscin (r²= 0.9999), and between 0.3 and 1087.5 μg/mL for rutin (r²= 0.9997). The limit(s) of detection and quantification for protodioscin were 1.6 μg/mL and 3.13 μg/mL, respectively, and for rutin 0.2 μg/mL and 0.3 μg/mL, respectively. White asparagus spears and the crown of the plants were revealed to be rich sources of protodioscin and contained 2.59 to 10.4 mg/g dry weight. Green asparagus spears, particularly the upper portion, were rich in rutin and contained between 1.51 and 7.29 mg/g dry weight.     

Effect of cultivars and deep freeze storage on saponin content of white asparagus spears (Asparagus officinalis L.)

A method was developed to prepare saponin samples of asparagus spears by Solid Phase Extraction (SPE) and to analyse these extracts by High Performance Thin Layer Chromatography (HPTLC). We chose six asparagus cultivars grown in Germany and measured total saponin contents of approximately 0.14–0.80 g kg⁻¹ fresh weight (fw). Among these six cultivars grown under eaqual conditions ‘Grolim’ showed the highest levels of saponins while ‘Huchels Alpha’ had the lowest contents. The other four cultivars gave intermediate levels. Asparagus stored at −18°C subsequently resulted in maintenance of saponins during 20 weeks of storage. Up to six saponins were found in the extracted samples, but three of them were the main compounds with approximately 90% of the total saponin content. Two main saponins (AS 1 and AS 2) were characterised by mass spectrometry as protodioscin and methyl-protodioscin.     

Constitutive Effects of Lead on Aryl Hydrocarbon Receptor Gene Battery and Protection by β‐carotene and Ascorbic Acid in Human HepG2 Cells

Lead (Pb) is an environmental pollutant that can get entry into human body through contaminated foods, drinks, and inhaled air leading to severe biological consequences, and has been responsible for many deaths worldwide. The objectives of this study were 1st to investigate the modulatory effects of environmentally relevant concentrations of Pb on AhR gene battery, which is controlling xenobiotics metabolism. 2nd, trials to reduce Pb‐induced adverse effects were done using some phytochemicals like β‐carotene or ascorbic acid. Human hepatoma (HepG2) cell lines were exposed to a wide range of Pb concentrations varying from physiological to toxic levels (0 to 10 mg/L) for 24 h. High Pb concentrations (1 to 10 mg/L) significantly reduced phase I (CYP1A1 and 1A2) and phase II (UGT1A6 and NQO1) xenobiotic metabolizing enzyme mRNA expression in a mechanistic manner through the AhR regulation pathway. Additionally, these Pb concentrations induced oxidative stress in HepG2 cells in terms of production of reactive oxygen species (ROS) and induced heme oxygenase‐1 mRNA expression in a concentration‐dependent phenomenon. Coexposure of HepG2 cells to physiological concentrations of some micronutrients, like β‐carotene (10 μM) or ascorbic acid (0.1 mM), along with Pb (1 mg/L) for 24 h significantly reduced the levels of ROS production and recovered AhR mRNA expression into the normal levels. Thus, consumption of foods rich in these micronutrients may help to reduce the adverse effects of lead in areas with high levels of pollution.     

Physical, chemical and microbiological changes in stored green asparagus spears as affected by coating of silver nanoparticles-PVP

Silver nanoparticles have recently gained increasing interests due to their antimicrobial activities in food processing applications. The aim of this study was to evaluate the effect of silver nanoparticles-PVP coating on weight loss, ascorbic acid, total chlorophyll, crude fiber, color, firmness and microbial qualities of asparagus spears stored at 2 and 10 °C. Asparagus samples were first sanitized with 100 mg l⁻¹ sodium hypochloride solution for 15 min. They were then immersed in coating solution containing silver nanoparticles for 3 min at room temperature. During 25-day storage at 2 or 10 °C, the coated asparagus demonstrated lower weight loss, greener color and tender texture compared with the control samples. The growth of microorganism was significantly hindered by the coating. Based on comprehensive comparison and evaluation, asparagus spears coated by silver nanoparticles could be kept in good quality for 25 days at 2 °C and for 20 days at 10 °C.     

Influence of Ca2+, K+ and NO3− fertilisation on nutritional quality of pepper

A study was conducted in order to assess the effect of different fertilisation levels of Ca²⁺, K⁺ and NO₃^? on the bioactive nutrient content in red pepper (Capsicum annuum L) fruits. The experiment was carried out in a greenhouse, under hydroponic culture. Lycopene, β‐carotene, vitamin C, total phenolic compound, sugar, nitrate and potassium contents and antioxidant activity were determined. Increasing Ca²⁺ and NO₃^? concentrations in the root medium increased the lycopene and β‐carotene contents in pepper. Antioxidant activity was determined in the hydrophilic (HAA) and lipophilic (LAA) fractions. HAA was increased by intermediate and high Ca²⁺ concentrations in the culture medium. However, LAA was raised only by NO₃^? treatments. Vitamin C, sugar and total phenolic acid contents were not affected by Ca²⁺ or NO₃^? treatments. K⁺ treatments had no effect on nutritional quality of pepper. An increased supply of Ca²⁺ and NO₃^? in the culture medium could constitute a useful practice for improving the nutritional attributes of pepper as well as its commercial quality. Copyright © 2004 Society of Chemical Industry     

Effect of low‐dose irradiation on shelf life and microbiological safety of sliced carrot

Minimally processed non‐irradiated carrots (sliced) exhibited diverse microflora at initial level. During storage, bacterial number increased with the presence of pathogenic bacteria accompanied by a loss of total solids. On the other hand γ‐irradiation at an optimal dose of 2 kGy offered a pathogen‐free, hygienic product with insignificant losses in nutrients such as in sucrose, total carotenes and ascorbic acid content in comparison to controls and 2‐ to 4‐fold increased in shelf‐life at refrigeration temperature. The D₁₀ values of pathogens like Escherichia coli and Yersinia enterocolitica in carrot paste were in a lower range (0.12–0.26 kGy) compared with that of Listeria monocytogenes (0.3–0.5 kGy). The validity of the processing treatment (2 kGy) was challenged by artificially inoculating Listeria monocytogenes in the product. Thus, minimally processed carrots (sliced) are amenable to radiation treatment for extended storage stability and microbial safety. Copyright © 2005 Society of Chemical Industry     

Enhanced bioaccessibility of β‐carotene from yellow‐orange vegetables and green leafy vegetables by domestic heat processing

Effect of heat treatment involved in domestic cooking on the bioaccessibility of β‐carotene from yellow‐orange as well as green leafy vegetables was evaluated. Heat treatment of these vegetables by pressure‐cooking, stir‐frying and open‐pan boiling had a beneficial influence on the bioaccessibility of β‐carotene. The extent of increase in the per cent bioaccessibility of β‐carotene as a result of pressure‐cooking was 21–84%. Stir‐frying in presence of a small quantity of oil brought about an enormous increase in the bioaccessibility of β‐carotene from these vegetables, the extent of increase being 67–191%. Open‐pan boiling of vegetables increased the bioaccessibility of β‐carotene in the range 23–36%. Thus, among the three domestic heat processing methods, stir‐frying results in maximum bioaccessibility of this provitamin. The use of suitably heat‐processed vegetable sources of β‐carotene could form a dietary strategy to derive this micronutrient maximally by the population dependent on plant foods.     

In vitro accessibility of β‐carotene from cooked Sri Lankan green leafy vegetables and their estimated contribution to vitamin A requirement

Vitamin A deficiency is an important issue for public health in Sri Lanka, where pro‐vitamin A carotenoids from green leafy vegetables provide most of the dietary vitamin A. The objective of this study was to analyse the β‐carotene content of seven types of green leafy vegetables and calculate the contribution of one traditionally cooked portion to the recommended daily allowance (RDA) of retinol. The total amount and in vitro accessibility of β‐carotene were determined using HPLC. The in vitro method simulates the conditions in the human intestinal tract. The all‐trans‐β‐carotene content in the fresh blanched vegetables ranged from 149 µg g^?1 dry weight (DW) in leaves of Alternanthera sessilis (mukunuwanna) to 565 µg g^?1 DW in Amaranthus caudatus (thampala). One portion (100 g) of green leaves cooked without fat (coconut) only contributed from 140 to 180 µg mg^?1 of the recommended daily allowance. A. sessilis, Centella asiatica (gotukola), Spinacea oleracea (nivithi) and A. caudatus, cooked with coconut fat contributed 140–680 µg mg^?1. However, stir‐fried or ‘malluma’ preparations (with coconut products) of Sesbania grandiflora (kathurumurunga) and Manihot esculenta (manioc) may provide more than 1.59–4.37 times the RDA of retinol. These results show that not only the choice of green leaves used but also the addition of fat while cooking is of great importance. Copyright © 2005 Society of Chemical Industry     

Changes in Phenolic Content and Antioxidant Activity of Italian Extra‐Virgin Olive Oils during Storage

ABSTRACT: Phenolic composition and antioxidant activity of extra‐virgin olive oils extracted from several Italian varieties were studied at production and during storage. The antioxidant activity was measured according to the following tests: in the aqueous phase, by radical scavenging of the 2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) (ABTS) radical cation; and in the lipid phase, using the β‐carotene bleaching method. The phenolic content was not correlated to the oxidation indices (peroxide value and spectrophotometric constants). The phenolic contents and profiles of the various cultivars showed remarkable differences. The phenolic content was strongly correlated with the antioxidant activity measured according to the β‐carotene test and weakly correlated with the radical scavenging ability.     

β‐Carotene as a Membrane Antioxidant Probed by Cholesterol‐Anchored Daidzein

β‐Carotene is found to be more effective as an antioxidant in phosphatidylcholine (PC) liposomes when protecting against hydrophilic radicals compared to lipophilic radicals, as measured by the rate of formation of conjugated dienes. Daidzein alone is without effect, but decreases the antioxidative effect of β‐carotene for hydrophilic initiation and increases the effect for lipophilic initiation. The newly synthesized 7‐cholesterylglycol daidzein has the opposite effect for β‐carotene as antioxidant, with a strong enhancement for hydrophilic initiation and a slight decrease for lipophilic initiation. Redistributing β‐carotene to membrane surfaces by cholesterol‐anchoring of daidzein enhances protection against aqueous radicals significantly at the expense of protection against lipid‐derived radicals. Anchoring of daidzein to cholesterol is concluded to be useful as a mechanistic tool for controlling antioxidant distribution in membranes sensitive to radical damage, as supported by quantum mechanical calculation within the density function theory and further supported by fluorescence probes and fluorescence polarization probes.     

Effect of low‐cost storage and packaging on quality and nutritive value of fresh and dehydrated carrots

Fresh carrots (Daucus carota L cv ‘Nantes’) were packed in Netlon and ventilated low‐density polyethylene bags and stored in ambient, cool chamber and cool store conditions. Blanching and drying conditions were standardised and the sliced carrots were dehydrated to 7–9% moisture content using the best blanching and drying combination. Dehydrated carrots were packed in single and double layers of high‐density polyethylene bags and stored in ambient and cool store conditions for 9 months. The shelf‐life of fresh carrots varied from 3 to 20 days depending on the packaging and storage condition. A reduction in β‐carotene and ascorbic acid content and an increase in electrolyte leakage were observed during storage of fresh carrots. Blanching and drying caused a significant reduction in β‐carotene and ascorbic acid content, which further decreased during storage of dried product. The storage study of dried product showed that retention of β‐carotene and ascorbic acid was better in double‐packed and cool‐stored samples, and it also showed minimum browning during storage. © 2000 Society of Chemical Industry     

Enzyme activities,dietary fibre components and rheological properties of wholemeal flours from rye cultivars grown in Finland

Total and soluble dietary fibre, total and soluble pentosan and β‐glucan contents, activities of α‐amylase (EC 3.2.1.1) and endo‐β‐xylanase (EC 3.2.1.8) and viscous properties of aqueous suspensions of wholemeal flours during heating were determined in nine winter rye cultivars (Secale cereale L) grown in Finland in 1998–2001. There was marked annual and varietal differences in grain quality. In the rainy summer 1998 the yield was low, grains were small and dietary fibre content of the grains was high. Xylanase activity of the grains was high, which corresponded to the high content of soluble pentosans. In the dry summer of 1999, the pentosan content of the grains was low and β‐glucan content high. The effect of weather conditions and cultivar were also apparent in the differences in falling numbers, amylogram and swelling curve results. The two hybrid rye cultivars Esprit and Picasso had consistently highest falling numbers and amylogram peak viscosities. The activities of α‐amylase and xylanase had a moderate positive correlation with total pentosan content and the content of soluble pentosan. Xylanase activity had better correlation with the viscous properties of flour–water suspensions than α‐amylase. Surprisingly, α‐amylase activity had only a moderate negative correlation with falling number. Copyright © 2005 Society of Chemical Industry     

Carotenoids in pungent and non‐pungent peppers at various developmental stages grown in the field and glasshouse

Carotenoids in edible portions of plants can provide health benefits to humans. How growing conditions affect levels of carotenoids in pepper fruits as they mature is not well known. Five cvs of bell pepper (Bell Captain, Melody, North Star, Ranger, Red Beauty) and five cvs of pungent‐type peppers (Anaheim, Ancho, Cayenne, Pimento, Red Cherry) were grown in a glasshouse and in the field. Fruits were harvested at the green, turning (50% green) and mature red stages and analysed for levels of the carotenoids β‐cryptoxanthin, α‐carotene, β‐carotene, capsanthin, lutein and zeaxanthin and totals of these carotenoids. Levels of provitamin A: retinol equivalents (RE) were derived from levels of β‐cryptoxanthin, α‐carotene and β‐carotene. Levels of most carotenoids and RE were significantly higher in glasshouse‐grown plants, and most were higher in fruits at the red stage. Fruits of Ancho type had the most β‐cryptoxanthin, α‐carotene, β‐carotene, total carotenoids and RE, while fruits of Red Cherry type had the most capsanthin and zeaxanthin, and fruits of Bell Captain had the most lutein. Interactions of the main effects variables, ie location of production (field vs glasshouse), stage of development and cultivar, indicated differences in patterns of carotenoid levels and RE. The data indicated that growing conditions influenced carotenoid levels. The more consistent and protected conditions in the glasshouse may have caused carotenoid levels to be increased, especially at the red stage. Published in 2002 for SCI by John Wiley & Sons, Ltd     

A Comparison of the Antioxidant Potential of Wine and Beer

The antioxidant properties of two beers (an ale and a lager) and of two wines (a red Cabernet Sauvignon, and a white Chardonnay) have been compared using a range of assays: the Trolox assay, superoxide scavenging, hydroxyl scavenging and β‐carotene bleaching. When compared on an ‘as is’ basis, the red wine was shown to contain much more antioxidant potential than the other beverages with all the assays except the β‐carotene bleaching assay, which compares the ability of agents to prevent lipid oxidation. In this assay, beer performed best. When the beverages were compared on an equivalence of polyphenol basis, the superior performance of red wine was not evident, indeed white wine was the most potent in the Trolox assay and the superoxide scavenging tests, with beer again proving its superiority in the β‐carotene bleaching test. The study highlights the pitfalls of simply assuming that the superior performance of one product in a single assay means that it is inherently preferable as a source of antioxidants and pertinent issues remain the ability of the anti‐oxidants to access the tissues where they can exert a beneficial effect and the mode in which a substance needs to act in order to have a desirable impact on bodily health.     

Antioxidant activity of Potentilla fruticosa

The molecular structures of the radical scavenging compounds present in extracts of Potentilla fruticosa blossoms were elucidated and the antioxidant activities of various extracts were determined. The activities of the different fractions were monitored by off‐line and on‐line RP‐HPLC DPPH^? and ABTS^?+ scavenging methods. Twelve compounds were isolated and identified, namely ellagic acid, catechin, quercetin‐3‐β‐glucopyranoside, quercetin‐3‐β‐galactopyranoside, quercetin‐3‐β‐rutinoside, quercetin‐3‐β‐glucuronopyranoside, quercetin‐3‐α‐arabinofuranoside, kaempferol‐3‐β‐rutinoside, kaempferol‐3‐O‐β‐(6″‐O‐(E)‐p‐coumaroyl)glucopyranoside, rhamnetin‐3‐β‐glucopyranoside and rhamnetin‐3‐β‐galactopyranoside. The radical scavenging activity of each isolated compound was measured using DPPH^? and ABTS^?+ assays and compared with the activity of rosmarinic acid. Catechin and ellagic acid were found to be the most active radical scavengers. The antioxidant properties of plant fractions were assessed in model systems by measuring superoxide anion and hydrogen peroxide scavenging, β‐carotene bleaching, hexanal production in edible oil, peroxide formation, and the increase in UV absorbance in the course of oxidation. Copyright © 2004 Society of Chemical Industry