Antioxidant potential of mint (Mentha spicata L.) in radiation-processed lamb meat

The effectiveness of mint leaves, a common herb used in Indian cuisine, as a natural antioxidant for radiation-processed lamb meat was investigated. Mint extract (ME) had good total phenolic and flavonoid contents. It exhibited excellent antioxidant activity, as measured by β-carotene bleaching and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. It also showed a high superoxide- and hydroxyl-scavenging activity but low iron-chelating ability. A positive correlation was found between the reducing power and the antioxidant activity. The antioxidant activity of ME was found to be comparable to the synthetic antioxidant, butylated hydroxytoluene (BHT). The suitability of ME as an antioxidant was determined during radiation processing of lamb meat. ME retarded lipid oxidation, monitored as thiobarbituric acid-reactive substances (TBARS), in radiation-processed lamb meat. TBARS values of ME containing irradiated meat stored at chilled temperatures were significantly lower (p < 0.05) than samples without ME. After 4 weeks of chilled storage, TBARS in irradiated meat containing ME (0.1%) was half of that in untreated irradiated meat.     

Antioxidant activity of various extracts of old tea leaves and black tea wastes (Camellia sinensis L.)

The antioxidant activity of various extracts of old tea leaves (OTL) and black tea wastes (BTW) in comparison with that of green tea leaves (GTL) was evaluated. The highest extraction yield and antioxidant activity were found in hot water extracts of GTL. Hot water extracts of OTL and BTW showed the same statistically significant antioxidant activities (P < 0.05). Also, there was no statistically significant difference between the antioxidant activities of OTL and BTW extracts obtained by the other two extraction methods (ethyl acetate and methanolic methods) and, in some cases, BTW extracts acted even better than OTL extracts. The antioxidant activity of tea extracts was not concomitant with the development of their reducing power. This suggested that the antioxidant activity of tea extracts likely involves other mechanisms in addition to those of reductones. Totally, BTW extracts had antioxidant activities comparable with or even better than those of OTL extracts. Hence, OTL and BTW, which are often considered as agricultural wastes, can be used as potent natural antioxidative sources.     

Enzyme assisted extraction of luteolin and apigenin from pigeonpea [Cajanuscajan (L.) Millsp.] leaves

Luteolin and apigenin are naturally occurring flavones with a wide spectrum of pharmacological properties. In the present study, enzyme assisted extraction of luteolin and apigenin from pigeonpea leaves using commercial plant cell wall degrading enzyme preparations including cellulase, beta-glucosidase and pectinase were examined. We found that pectinase offered a better performance in enhancement of the extraction yields of luteolin and apigenin than cellulase and beta-glucosidase. The pectinase assisted extraction process was further optimized by varying different parameters such as pectinase concentration, time of incubation, pH of pectinase solution, and incubation temperature. The optimum parameters were obtained as follows: 0.4 mg/ml pectinase, incubation for 18 h at 30–35 °C, pH of pectinase solution 3.5–4. Under the optimum conditions, the extraction yields of luteolin and apigenin achieved 0.268 and 0.132 mg/g in pectinase treated sample, which increased 248% and 239%, respectively, compared with the untreated ones.     

Antioxidant potential of curry (Murraya koenigii L.) and mint (Mentha spicata) leaf extracts and their effect on colour and oxidative stability of raw ground pork meat during refrigeration storage

The aim of this study was to investigate the antioxidant activity of different solvent extracts of curry and mint leaf and their effect on colour and oxidative stability of raw ground pork meat stored at 4 ± 1 °C. The results indicated that among the two individual leaf categories, the ethanol extract of curry leaf (EHEC) and the water extract of mint leaf (WEM) showed higher DPPH and ABTS⁺ activity. EHEC also exhibited the highest total phenolic contents while these were the lowest for WEM. WEM showed the highest superoxide anionic scavenging activity (%). The pork meat samples treated with EHEC and WEM showed a decrease in the Hunter L- and a-values and a increase in b-value during storage at 4 °C. However, the pH and TBARS values were higher in control samples irrespective of storage periods. In conclusion, EHEC and WEM have the potential to be used as natural antioxidants to minimise lipid oxidation of pork products.     

Ultrasound-assisted extraction of polyphenols (flavanone glycosides) from orange (Citrus sinensis L.) peel

The present study reports on the extraction of polyphenols especially flavanones from orange (Citrus sinensis L.) peel by using ethanol as a food grade solvent. After a preliminary study showing that the best yield of extraction was reached for a particle size of 2 cm², a response surface methodology (RSM) was launched to investigate the influence of process variables on the ultrasound-assisted extraction (UAE) followed by a central composite design (CCD) approach. The statistical analysis revealed that the optimised conditions were a temperature of 40 °C, a sonication power of 150 W and a 4:1 (v/v) ethanol:water ratio. The high total phenolic content (275.8 mg of gallic acid equivalent/100 g FW), flavanone concentrations (70.3 mg of naringin and 205.2 mg of hesperidin/100 g FW) and extraction yield (10.9 %) obtained from optimised UAE proved its efficiency when compared with the conventional method. Furthermore, the antioxidant activity determined by the DPPH and ORAC tests confirmed the suitability of UAE for the preparation of antioxidant-rich plant extracts.     

Antioxidant properties of various solvent extracts of mulberry (Morus indica L.) leaves

The antioxidant properties and total phenolic contents of methanol, acetone and water extracts of mulberry (Morus indica L.) leaves were examined. Various experimental models including iron (III) reducing capacity, total antioxidant capacity, DPPH radical scavenging activity and in vitro inhibition of ferrous sulphate-induced oxidation of lipid system were used for characterization of antioxidant activity of extracts. The three extracts showed varying degrees of efficacy in each assay in a dose-dependent manner. Methanolic extract with the highest amount of total phenolics, was the most potent antioxidant in all the assays used. In addition, the effect of temperature (50 °C and 100 °C), pH (3, 5, 7, 9 and 11) and storage (5 °C) on the antioxidant activity of methanolic extract was investigated. The antioxidant activity of the extract remained unchanged at 50 °C and was maximum at neutral pH. The extract stored at 5 °C in the dark was stable for 30 days after which the antioxidant activity decreased (p ? 0.05) gradually. On the basis of the results obtained, mulberry leaves were found to serve as a potential source of natural antioxidants due to their marked antioxidant activity.     

Optimisation of the extraction and processing conditions of chamomile (Matricaria chamomilla L.) for incorporation into a beverage

The total phenols, apigenin 7-glucoside, turbidity and colour of extracts from dried chamomile flowers were studied with a view to develop chamomile extracts with potential anti-inflammatory properties for incorporation into beverages. The extraction of all constituents followed pseudo first-order kinetics. In general, the rate constant (k) increased as the temperature increased from 57 to 100 °C. The turbidity only increased significantly between 90 and 100 °C. Therefore, aqueous chamomile extracts had maximum total phenol concentration and minimum turbidity when extracted at 90 °C for 20 min. The effect of drying conditions on chamomile extracted using these conditions was determined. A significant reduction in phenol concentration, from 19.7 ± 0.5 mg/g GAE in fresh chamomile to 13 ± 1 mg/g GAE, was found only in the plant material oven-dried at 80 °C (p ? 0.05). The biggest colour change was between fresh chamomile and that oven-dried at 80 °C, followed by samples air-dried. There was no significant difference in colour of material freeze-dried and oven-dried at 40 °C.     

Optimisation of the aqueous extraction conditions of phenols from meadowsweet (Filipendula ulmaria L.) for incorporation into beverages

Meadowsweet was extracted in water at a range of temperatures (60–100 °C), and the total phenols, tannins, quercetin, salicylic acid content and colour were analysed. The extraction of total phenols followed pseudo first-order kinetics, the rate constant (k) increased from 0.09 ± 0.02 min⁻¹ to 0.44 ± 0.09 min⁻¹, as the temperature increased from 60 to 100 °C. An increase in temperature from 60 to 100 °C increased the concentration of total phenols extracted from 39 ± 2 to 63 ± 3 mg g⁻¹ gallic acid equivalents, although it did not significantly affect the proportion of tannin and non-tannin fractions. The extraction of quercetin and salicyclic acid from meadowsweet also followed pseudo first-order kinetics, the rate constant of both compounds increasing with an increase in temperature up until 90 °C. Therefore, the aqueous extraction of meadowsweet at temperatures at or above 90 °C for 15 min yields extracts high in phenols, which may be added to beverages.     

Retention of aroma compounds from Mentha piperita essential oil by cyclodextrins and crosslinked cyclodextrin polymers

In this paper, the controlled release of aroma compounds from cyclodextrins (CDs) and CD polymers was studied by multiple headspace extraction (MHE) experiments. Mentha piperita essential oil was obtained by Soxhlet extraction and identification of the major compounds was performed by GC–MS analysis. Menthol, menthone, pulegone and eucalyptol were identified as the major components. Retention of standard compounds in the presence of different CDs and CD polymers has been realised by static headspace gas chromatography (SH-GC) at 25 °C in the aqueous or gaseous phase. Stability constants for standard compounds and for compounds in essential oil have been also determined with monomeric CD derivatives. The obtained results indicated the formation of a 1:1 inclusion complex for all the studied compounds. Molecular modelling was used to investigate the complementarities between host and guest. This study showed that β-CDs were the most versatile CDs and that β-CD polymers could perform the controlled release of aroma compounds.     

Preventive effects of guava (Psidium guajava L.) leaves and its active compounds against α-dicarbonyl compounds-induced blood coagulation

Diabetes is associated with a hypercoagulable state which may accelerate atherosclerosis, thrombosis and the diabetic microvascular complication. Endogenously produced α-dicarbonyl compounds are linked to the pathophysiology of diabetic complications. The effects of α-dicarbonyl compounds on coagulation parameters in vitro and the anticoagulant activities of aqueous extracts from guava leaves were examined. Incubation of plasma with glyoxal or methylglyoxal at 0.1 mM showed a significant decrease in thrombin clotting time (TT) (P < 0.05). However, they exhibited slight prolongation of the prothrombin time (PT) at 0.5 mM and no effect on the activated partial thromboplastin time (APTT). In order to define the action mechanism of the hypercoagulant activity, coagulation factors such as fibrinogen and antithrombin III activity were evaluated. The fibrinogen contents in plasma were decreased slightly with increasing concentrations of glyoxal and methylglyoxal. Moreover, methylglyoxal inhibited antithrombin III activity and over 80% of the activity was lost at 1.2 mM methylglyoxal. In contrast, guava leaf extracts exhibited significant inhibition of TT shortening induced by methylglyoxal. Guava leaf extracts and its active phenolic compounds including ferulic acid, gallic acid and quercetin also displayed a protective effect against methylglyoxal-induced loss of activity of antithrombin III. Thus, guava leaf extracts are a potent antiglycative agent and anticoagulant, which can be of great value in the preventive glycation-associated cardiovascular diseases in diabetes.     

Optimisation of novel method for the extraction of steviosides from Stevia rebaudiana leaves

Stevioside, a diterpene glycoside, is well known for its intense sweetness and is used as a non-caloric sweetener. Its potential widespread use requires an easy and effective extraction method. Enzymatic extraction of stevioside from Stevia rebaudiana leaves with cellulase, pectinase and hemicellulase, using various parameters, such as concentration of enzyme, incubation time and temperature, was optimised. Hemicellulase was observed to give the highest stevioside yield (369.23 ± 0.11 μg) in 1 h in comparison to cellulase (359 ± 0.30 μg) and pectinases (333 ± 0.55 μg). Extraction from leaves under optimised conditions showed a remarkable increase in the yield (35 times) compared with a control experiment. The extraction conditions were further optimised using response surface methodology (RSM). A central composite design (CCD) was used for experimental design and analysis of the results to obtain optimal extraction conditions. Based on RSM analysis, temperature of 51-54 °C, time of 36-45 min and the cocktail of pectinase, cellulase and hemicellulase, set at 2% each, gave the best results. Under the optimised conditions, the experimental values were in close agreement with the prediction model and resulted in a three times yield enhancement of stevioside. The isolated stevioside was characterised through ¹H-NMR spectroscopy, by comparison with a stevioside standard.     

Hollow fibre-based liquid phase microextraction combined with high-performance liquid chromatography for the analysis of flavonoids in Echinophora platyloba DC. and Mentha piperita

A simple, inexpensive and efficient three phase hollow fibre liquid phase microextraction (HF-LPME) technique combined with HPLC was used for the simultaneous determination of flavonoids in Echinophora platyloba DC. and Mentha piperita. Different factors affecting the HF-LPME procedure were investigated and optimised. The optimised extraction conditions were as follows: 1-octanol as an organic solvent, pH_donor = 2, pH_acceptor = 9.75, stirring rate of 1000 rpm, extraction time of 80 min, without addition of salt. Under these conditions, the enrichment factors ranged between 146 and 311. The values of intra and inter-day relative standard deviations (RSD) were in the range of 3.18–6.00% and 7.25–11.00%, respectively. The limits of detection (LODs) ranged between 0.5 and 7.0 ng mL⁻¹. Among the investigated flavonoids quercetin was found in E. platyloba DC. and luteolin was found in M. piperita. Concentration of quercetin and luteolin was 0.015 and 0.025 mg g⁻¹ respectively.     

Insecticidal activities of constituents identified in the essential oil from leaves of Chamaecyparis obtusa against Callosobruchus chinensis (L.) and Sitophilus oryzae (L.)

Analysis by gas chromatography-mass spectrometry led to the identification of 20 volatiles from the steam distilled oil of the leaves from Chamaecyparis obtusa Siebold et Zuccarni. Seven constituents of the oil were tested for contact and fumigant activity against adults of Callosobruchus chinensis (L.) and Sitophilus oryzae (L.). Responses varied with compound and dose rather than increasing exposure time beyond 1 or 2 days. In the impregnated-paper test with the constituents [bornyl acetate, (+)-limonene, myrcene, α-phellandrene, α-pinene, sabinene and terpinolene], at 0.1 mg/cm², bornyl acetate, α-phellandrene and terpinolene caused 97%, 97% and 87% mortality, respectively, against C. chinensis adults 1 day after treatment. At 0.05 mg/cm², moderate activity was achieved with bornyl acetate (56% mortality), α-phellandrene (75%) and terpinolene (55%). Against S. oryzae adults, at 0.26 mg/cm², terpinolene caused 93% mortality 2 days after treatment, whereas 80% mortality 4 days after treatment was observed with bornyl acetate and α-phellandrene. The toxicity of these compounds was significantly decreased at 0.18 mg/cm². In a fumigation test with S. oryzae adults, bornyl acetate and terpinolene were much more effective in sealed containers than in open ones, indicating that the insecticidal activity of these compounds was largely attributable to fumigant action. These naturally occurring materials derived from leaves of Chamaecyparis could be useful for managing populations of C. chinensis and S. oryzae.     

Chicoric acid found in basil (Ocimum basilicum L.) leaves

This is the first report to identify the presence of chicoric acid (cichoric acid; also known as dicaffeoyltartaric acid, which is a caffeic acid derivatized with tartaric acid) in basil leaves. Rosmarinic acid, chicoric acid and caftaric acid (in the order of most abundant to least; all derivatives of caffeic acid) were identified in fresh basil leaves. Rosmarinic acid was the main phenolic compound found in both leaves and stems. Chicoric acid was not detected in sweet basil stems, although a small amount was present in Thai basil stems. Other cinnamic acid monomers, dimers and trimers were also found in minor quantities in both stems and leaves. Basil polyphenolic contents were determined by blanched methanol extraction, followed by HPLC/DAD analysis. The characterization of the polyphenolics found in the basil extracts were performed by HPLC/DAD/ESI–MS/MS and co-chromatographed with purchased standard. The influence of inoculation with an arbuscular mycorrhizal fungus (AMF), Glomus intraradices, on plant phenolic composition was studied on two basil cultivars,‘Genovese Italian’ and ‘Purple Petra’. Inoculation with AMF increased total anthocyanin concentration of ‘Purple Petra’ but did not alter polyphenolic content or profile of leaves and stems, of either cultivar, compared to non-inoculated plants. In the US diet, basil presents a more accessible source of chicoric acid than does Echinacea purpurea, in which it is the major phenolic compound.     

Phytosterol content of sea buckthorn (Hippophae rhamnoides L.) seed oil: Extraction and identification

Phytosterols in sea buckthorn (Hippophae rhamnoides L.) seed oil extracted by cold pressing, hexane, and supercritical carbon dioxide were identified by GC–MS and FID. Compounds identified were campesterol, clerosterol, lanosterol, sitosterol, β-amyrin, sitostanol, Δ⁵-avenasterol, Δ²⁴⁽²⁸⁾-stigmasta-en-ol, α-amyrin, Δ^5,24(25)-stigmastadienol, lupeol, gramisterol, Δ⁷-sitosterol, cycloartenol, cycloeucalenol, Δ⁷-avenasterol, 28-methylobtusifoliol, 24-methylenecycloartanol, erythrodiol, citrostadienol, uvaol, and oleanol aldehyde. Sitosterol and Δ⁵-avenasterol were, quantitatively, the most important phytosterols. Total sterols and most individual sterols differed significantly (P ? 0.05) among all three extraction methods with supercritical carbon dioxide extracting the highest total sterol levels (1640 mg/100 g oil) and cold pressed the lowest levels (879 mg/100 g oil).     

Enzyme-assisted extraction of volatiles from cumin (Cuminum cyminum L.) seeds

The effect of various enzymes on the extraction of the volatile oil of cumin (Cuminum cyminum L.) is reported in the present study. The oil yield, after pre-treatment of cumin seeds with cellulase, pectinase, protease and Viscozyme, was in the range 3.2–3.3% compared to 2.7% in a control sample. Profiling of the cumin oil by GC–MS showed that the total hydrocarbon content was 63.7%, 66.1% and 70.1% in control, cellulase and Viscozyme treated samples, respectively. However, there was no change in the content of cuminaldehyde, the principal flavour-impact constituent, in any of the volatile oils. The study demonstrated that enzymes facilitated the extraction of cumin oil with increase in oil yield, with little change in either flavour profile or physicochemical properties of the oil.     

Functional lupin seeds (Lupinus albus L. and Lupinus luteus L.) after extraction of α-galactosides

Functional lupin seeds from two different cultivars of white (Lupinus albus L.) and yellow lupin (Lupinus luteus L.) each, were obtained by extraction of α-galactosides. The effect of extraction of α-galactosides from lupin seeds on different nutritional parameters (protein, fat, ash, dietary fibre, starch, sucrose, and vitamins B₁, B₂, E and C) and antinutritional factors (α-galactosides, trypsin inhibitor activity and inositol phosphates) were studied. In lupin seeds, α-galactosides were effectively removed and processed seeds contained very low amounts of flatulence causing factors (∼0.5–1%). Protein, fat and starch contents showed high retention in processed seeds (up to ∼130%). Sucrose and soluble dietary fibre, however, decreased significantly as a result of processing and retentions ranged from 10% to 60%, depending on the variety studied. Vitamins B₁, B₂, E and C were also reduced. Trypsin inhibitor activity was detected only in yellow lupin cultivars and inositol phosphate content was modified slightly after extraction. In summary, the functional lupin seeds, with low contents of α-galactosides, are a product of nutritional importance due to their high protein content, dietary fibre and fat contents as well as acceptable levels of thiamin, riboflavin and vitamin E. They can be incorporated as a proteic source, not only in animal feeding but also in a wide range of foods.     

Optimisation of accelerated solvent extraction of antioxidant compounds from rosemary (Rosmarinus officinalis L.), marjoram (Origanum majorana L.) and oregano (Origanum vulgare L.) using response surface methodology

The present study optimised the accelerated solvent extraction (ASE) conditions (Dionex ASE® 200, USA) to maximise the antioxidant capacity of the extracts from three spices of Lamiaceae family; rosemary, oregano and marjoram. Optimised conditions with regard to extraction temperature (66–129 °C) and solvent concentration (32–88% methanol) were identified using response surface methodology (RSM). For all three spices results showed that 129 °C was the optimum temperature in order to obtain extracts with high antioxidant activity. Optimal methanol concentrations with respect to the antioxidant activity of rosemary and marjoram extracts were 56% and 57% respectively. Oregano showed a different response to the effect of methanol concentration and was optimally extracted at 33%. The antioxidant activity yields of the optimal ASE extracts were significantly (p < 0.05) higher than solid/liquid extracts. The predicted models were highly significant (p < 0.05) for both total phenol (TP) and ferric reducing antioxidant property (FRAP) values in all the spices with high regression coefficients (R²) ranging from 0.952 to 0.999.     

Hazel (Corylus avellana L.) leaves as source of antimicrobial and antioxidative compounds

Aqueous extracts of leaves of different hazel (Corylus avellana L.) cultivars (Cv. M. Bollwiller, Fertille de Coutard and Daviana), were analysed by reversed-phase HPLC/DAD for the definition of their phenolic composition. Antioxidant potential was assessed by the reducing power assay, and the scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and β-carotene linoleate model system. Their antimicrobial capacity was also tested against Gram positive (Bacillus cereus, Bacillus subtilis, Staphylococcus aureus) and Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae) and fungi (Candida albicans, Cryptococcus neoformans). Eight phenolic compounds were identified: 3-, 4- and 5-caffeoylquinic acids, caffeoyltartaric acid, p-coumaroyltartaric acid, myricetin-rhamnoside, quercetin 3-rhamnoside and kaempferol 3-rhamnoside. A p-coumaric acid, three myricetin and one quercetin derivatives were also detected. The hazel leaves extract presented high antioxidant activity in a concentration-dependent way, in general with similar behaviour of all cultivars. Gram positive bacteria revealed to be very sensitive to hazel leaf extract (MIC 0.1 mg/ml for B. cereus and S. aureus and 1 mg/ml for B. subtilis). However, Gram negative and the fungi displayed much lower sensitivity, being P. aeruginosa and C. albicans resistant at 100 mg/ml. Cv. M. Bollwiller exhibited the most potent antimicrobial activity.     

Isolation and viscometric characterization of hydrocolloids from mulberry (Morus alba L.) leaves

Hydrocolloid in mulberry leaves was extracted with water or sodium bicarbonate, and characterized rheologically in a highly dilute to a semi-dilute regime. Mulberry leaf hydrocolloid was composed of mainly carbohydrate with high levels of uronic acid. The hydrodynamic behavior of mulberry leaf hydrocolloid in deionized water demonstrated a typical polyelectrolyte behavior in the dilute domain, as indicated by a nonlinear Huggins' plot. Intrinsic viscosity value for alkaline-extracted (Alk) and water-extracted (Hw) hydrocolloid was around 7.25 dL/g and 3.61 dL/g, respectively. The specific viscosity versus concentration plot for both Alk and Hw exhibited a power-law dependence on concentration, with an onset of molecular entanglement occurring at a concentration of around 0.6 g/dL and 1.8 g/dL, respectively. Coil-overlap parameter for Alk and Hw was in the range of 4.35–6.61. The relative chain stiffness parameter (B) for Alk and Hw was in the range of 0.004–0.013, indicating a stiff backbone.