Antioxidant capacity and phenolic content of selected commercially available cruciferous vegetables

Antioxidant activity, free radical scavenging activity and phenolic content of red cabbage (Brassica oleracea var. capitata rubra), Chinese cabbage (Brassica rapa pekinensis var cylindrica), green cabbage (Brassica oleracea var capitata), mustard cabbage (Brassica juncea var rugosa) and Chinese white cabbage (Brassica rapa var chinensis), grown in Malaysia, were evaluated. Red cabbage had the highest antioxidant activity and phenolic content compared to the other cruciferous vegetables studied (p < 0.05). The contributions of all cruciferous vegetables to the antioxidant activity was >79%. The radical scavenging activity was in the order of Chinese white cabbage > red cabbage > mustard cabbage > Chinese cabbage > green cabbage. There was a significant difference (p < 0.05) in the means of scavenging activity observed between cabbage, Chinese cabbage and Chinese mustard. Phenolic content was significantly different (p < 0.05) among all the cruciferous vegetables studied, and was in the order of red cabbage > Chinese white cabbage > green cabbage > Chinese cabbage >mustard cabbage. The study indicated that red cabbage possessed the highest antioxidant capacity and phenolic compounds concentration among all the cruciferous vegetables studied.     

Nutritive value, antioxidant and antimicrobial properties of Struchium sparganophora leaves

Struchium sparganophora leaf is a green leafy vegetable popularly used in soup preparations in processed and unprocessed forms in Nigeria. Fresh leaves of S. sparganophora were soaked overnight to remove its bitterness, before determination of the nutrient and antinutrient content, while sun-dried S. sparganophora leaves were extracted with rectified spirit. The antioxidant and antimicrobial properties of the extracts were subsequently determined. The result of the study revealed that the fresh leaf has high nutrient (protein, fat, crude fiber, and mineral) but low antinutrient (tannin and phytate) content. However, processing of the S. sparganophora leaf caused a significant decrease (P < .05) in both the nutrient and antinutrient contents. The ethanolic extract of the leaf contains alkaloids, tannin, saponins, phlobatannin, anthraquinone, and glycosides; furthermore, the extract has high antioxidant activity as typified by its high total phenol (5.4 g/100 g) content, reducing power (2.50 OD(700)), and free radical scavenging ability (65.2%). In addition, the extract (1.0 mg/mL) inhibited the growth of some pathogenic bacteria [Shigella dysenteriae (zone of inhibition 17.0 mm), Staphylococcus aureus (11.0 mm)] and fungi [Candida albicans (18.0 mm), Penicillium sp. (14.0 mm), Saccharomyces cerevisiae (15.0 mm)]. The inhibition of the bacterial and fungal growth was dose dependent. However, the same concentration of the extract did not inhibit the growth of Escherichia coli, Proteus sp., Pseudomonas aeruginosa, and Klebsiella sp., as well as the growth of the following fungi: Aspergillus fumigatus, Fusarium solani, and Aspergillus flavus. It could therefore be inferred that the leaf of S. sparganophora is promising both nutritionally and medicinally because of its high nutrient content, low antinutrient content, and arrays of pharmaceutically active phytochemicals with high levels of antioxidant and antimicrobial activity.     

Antioxidant and free radical scavenging activities of some leafy vegetables

Some leafy vegetables were studied for their nutritional composition, antioxidant and free radical scavenging activities. The aerial parts of Coriandrum sativum, Spinacia oleracea, Trigonella corniculata and Trigonella foenum-graecum showed lower inhibitory concentration values (4.1-7.9 mg/ml), efficiency concentration values (178-321 mg/mg DPPH) and higher values of anti-radical power (0.31-0.51) as compared with their seeds. Thermal treatment reduced the total phenolic contents, antioxidant and free radical scavenging activities. The leaves of C. sativum were found with good amounts of caffeic acid, ferulic acid, gallic acid and chlorogenic acid.     

Customized cooking method improves total antioxidant activity in selected vegetables

The present study compares water-soluble phenolic content (WPC) and antioxidant activities in Chinese long bean (Vigna unguiculata), bitter gourd (Momordica charantia), water convolvulus (Ipomoea aquatica) and broccoli (Brassica olearacea) prior to and after subjecting to boiling, microwaving and pressure cooking. The total antioxidant activity was increased in cooked water convolvulus, broccoli and bitter gourd, estimated based on the ferric reducing antioxidant power, the Trolox equivalent antioxidant capacity and 2,2-diphenyl-1-picryl-hydrazyl radical scavenging activity. Pressure cooking did not cause any significant decline in the antioxidant property. Boiling generally improved the overall antioxidant activity in all the vegetables. Correlation analysis suggests that WPC contributed to significant antioxidant activities in these vegetables. Thus, prudence in selecting an appropriate cooking method for different vegetables may improve or preserve their nutritional value.     

Antioxidant and free radical scavenging activities of some leafy vegetables

Some leafy vegetables were studied for their nutritional composition, antioxidant and free radical scavenging activities. The aerial parts of Coriandrum sativum, Spinacia oleracea, Trigonella corniculata and Trigonella foenum-graecum showed lower inhibitory concentration values (4.1–7.9 mg/ml), efficiency concentration values (178–321 mg/mg DPPH) and higher values of anti-radical power (0.31–0.51) as compared with their seeds. Thermal treatment reduced the total phenolic contents, antioxidant and free radical scavenging activities. The leaves of C. sativum were found with good amounts of caffeic acid, ferulic acid, gallic acid and chlorogenic acid.     

Customized cooking method improves total antioxidant activity in selected vegetables

The present study compares water-soluble phenolic content (WPC) and antioxidant activities in Chinese long bean (Vigna unguiculata), bitter gourd (Momordica charantia), water convolvulus (Ipomoea aquatica) and broccoli (Brassica olearacea) prior to and after subjecting to boiling, microwaving and pressure cooking. The total antioxidant activity was increased in cooked water convolvulus, broccoli and bitter gourd, estimated based on the ferric reducing antioxidant power, the Trolox equivalent antioxidant capacity and 2,2-diphenyl-1-picryl-hydrazyl radical scavenging activity. Pressure cooking did not cause any significant decline in the antioxidant property. Boiling generally improved the overall antioxidant activity in all the vegetables. Correlation analysis suggests that WPC contributed to significant antioxidant activities in these vegetables. Thus, prudence in selecting an appropriate cooking method for different vegetables may improve or preserve their nutritional value.     

Antioxidant activity, ascorbic acid and total phenol of exotic fruits occurring in Brazil

The antioxidant activity, ascorbic acid and phenolic content were studied in 10 exotic fruits from Brazil: abiu, acerola, wax jambu, cashew, mamey sapote, carambola or star fruit, Surinam cherry, longan, sapodilla and jaboticaba. The ascorbic acid was determined by 2,6-dichloroindophenol titrimetic methods and total phenols were measured colorimetrically using the Folin-Ciocalteu reagent. The antioxidant activity was investigated with three different methods: hypochlorous acid scavenging activity, 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation decolorization assay, and 2,2-diphenyl-1-picrylhydrazyl radical scavenging method. The highest content of vitamin C (1,525.00 mg/100 g pulp) occurred in acerola. The total phenol content was higher in abiu, acerola, Surinam cherry and sapodilla. In relation to antioxidant activity, acerola has showed the great values in all three different methods tested. It was found that the fruits have a significant antioxidant effect when tested by each method, respectively, and these antioxidant capacities are promising. The sample concentration also influenced its antioxidant power.     

The ecology of famine: An overview†

In the Ghanaian diet, ascorbic acid may be derived from a number of plant sources. For the majority of the population the main sources are the starchy roots, tubers and starchy fruits and, when available, the leafy and other vegetables. Data are presented on the ascorbic acid content of 14 fruits, one nut, six starchy roots and tubers, one starchy fruit and 17 leafy and other vegetables. Investigations were also carried out on storage and cooking effects. Cooking losses showed a considerable degree of variation depending upon the class of foodstuff and cooking method employed. The starchy roots, tubers, and starchy fruits were found to retain some ascorbic acid after cooking, while the greatest losses occured in the leafy vegetables. The findings are discussed with respect to work reported by earlier workers and in relation to the Vitamin C status of the population.     

Antioxidant and antimicrobial properties of some lichens and their constituents

The aim of this study is to examine the in vitro antioxidant and antimicrobial activities of the acetone, methanol, and aqueous extracts of the lichens Cladonia furcata (many-forked Cladonia), Hypogymnia physodes (puffed lichen), and Umbilicaria polyphylla (manyleaf navel lichen) and the antimicrobial activity of fumarprotocetraric acid, gyrophoric acid, and physodic acid isolated from the respective lichen species. Antioxidant activity was evaluated by five different methods: free radical scavenging, superoxide anion radical scavenging, reducing power, determination of total phenolic compounds, and determination of total flavonoid content. U. polyphyla exhibited more powerful antioxidant activities than the other lichen species examined: methanol extracts of U. polyphyla showed 90.08% free radical scavenging activities (the ratio was greater than those of standard antioxidants). Moreover, the extracts tested had effective reducing power and superoxide anion radical scavenging. Total contents of phenol and flavonoid in extracts were determined as pyrocatechol equivalents and as rutin equivalents, respectively. A significant strong relationship between total phenolic and flavonoid contents and their antioxidative activities was observed. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method against six species of bacteria and 10 species of fungi. In general, the lichen extracts tested and their respective acids had relatively strong antimicrobial activity against the microorganisms tested. The present study shows that the lichen species tested demonstrated strong antioxidant and antimicrobial activities. The results suggest that lichens may be used as good sources of natural antioxidants and for pharmaceutical purposes in treating various diseases.     

Flavonoid content in ethanolic extracts of selected raw and traditionally processed indigenous foods consumed by vulnerable groups of Kenya: antioxidant and type II diabetes-related functional properties

The present study evaluated the flavonoid content, antioxidant as well as type II diabetes-related enzyme inhibition activities of ethanolic extract of certain raw and traditionally processed indigenous food ingredients including cereals, legumes, oil seeds, tubers, vegetables and leafy vegetables, which are commonly consumed by vulnerable groups in Kenya. The vegetables exhibited higher flavonoid content (50–703 mg/100 g) when compared with the grains (47–343 mg/100 g). The ethanolic extract of presently studied food ingredients revealed 33–93% DPPH radical scavenging capacity, 486–6,389 mmol Fe(II)/g reducing power, 19–43% α-amylase inhibition activity and 14–68% α-glucosidase inhibition activity. Among the different food-stuffs, the drumstick and amaranth leaves exhibited significantly higher flavonoid content with excellent functional properties. Roasting of grains and cooking of vegetables were found to be suitable processing methods in preserving the functional properties. Hence, such viable processing techniques for respective food samples will be considered in the formulation of functional supplementary foods for vulnerable groups in Kenya.     

The effect of the germination temperature on the phytochemical content of broccoli and rocket sprouts

This study investigates the effect of different germination temperatures (10, 20 and 30?°C) on the phytochemical content as well as reducing and antioxidant capacity of broccoli and rocket sprouts. In both seeds and sprouts, the total glucosinolates and ascorbic acid contents did not differ between vegetables, while broccoli exhibited exceptionally higher polyphenols and greater reducing and antioxidant capacity compared to rocket. In both species, an increase in germination temperature positively affected the glucosinolate content. Ascorbic acid increased during germination without a difference among the three tested temperatures. The phenol content in broccoli sprouts increased when they were grown at 30?°C, but the amount decreased at the highest temperatures in rocket. The reducing and antioxidant capacities increased with germination, and higher indexes were detected at 10?°C, particularly in rocket. Different germination temperatures differentiate the health-promoting phytochemical content and antioxidant properties in broccoli and rocket sprouts.     

Flavonoid content in ethanolic extracts of selected raw and traditionally processed indigenous foods consumed by vulnerable groups of Kenya: antioxidant and type II diabetes-related functional properties

The present study evaluated the flavonoid content, antioxidant as well as type II diabetes-related enzyme inhibition activities of ethanolic extract of certain raw and traditionally processed indigenous food ingredients including cereals, legumes, oil seeds, tubers, vegetables and leafy vegetables, which are commonly consumed by vulnerable groups in Kenya. The vegetables exhibited higher flavonoid content (50-703?mg/100?g) when compared with the grains (47-343?mg/100?g). The ethanolic extract of presently studied food ingredients revealed 33-93% DPPH radical scavenging capacity, 486-6,389?mmol Fe(II)/g reducing power, 19-43% α-amylase inhibition activity and 14-68% α-glucosidase inhibition activity. Among the different food-stuffs, the drumstick and amaranth leaves exhibited significantly higher flavonoid content with excellent functional properties. Roasting of grains and cooking of vegetables were found to be suitable processing methods in preserving the functional properties. Hence, such viable processing techniques for respective food samples will be considered in the formulation of functional supplementary foods for vulnerable groups in Kenya.     

Multifunctional in vitro antioxidant evaluation of strawberry (Fragaria virginiana Dutch.)

Berries have shown the highest potential antioxidant activity among fruits using a unique antioxidant method. The antioxidant activity of aqueous-organic extracts of strawberry (Fragaria virginiana Dutch., var. camarosa) were determined using three methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH*) radical scavenging, antioxidant ferric-reducing power (FRAP), and inhibition of Cu(II)-catalysed in vitro human low-density lipoprotein (LDL) oxidation. A serving (100 g) of strawberry had a DPPH* activity equivalent to that of 183 mg vitamin C and to that of 483 mg vitamin E. In addition, strawberry extracts showed high efficiency in the FRAP assay and in the in vitro inhibition of LDL oxidation. Regression linear analysis between radical scavenging activity (EC50 parameter) and total phenol content from strawberry extracts gave a statistically significant correlation (r = 0.984, P < 0.05). In conclusion, strawberry showed significant antioxidant capacity in both aqueous and lipophilic models.     

Total phenolics and antioxidant capacity of indigenous vegetables in the southeast United States: Alabama Collaboration for Cardiovascular Equality Project

Collard greens, mustard greens, kale, okra, green onion, butter beans, butter peas, purple hull peas, rutabagas, and eggplant are frequently consumed by African Americans in the southeast United States. Sweet potato greens and purslane are two novel vegetables in this region. The objective of this study was to analyze total phenolics and antioxidant capacity in these indigenous vegetables. The total phenolic content was analyzed using the Folin-Ciocalteu method and ranged from 7.4 to 53.5 mg gallic acid equivalents per gram of dried sample. The antioxidant capacity was analyzed using the radical DPPH(?) scavenging capacity assay and oxygen radical absorbance capacity assay (ORAC). At a concentration of 10.0 mg dried vegetable equivalent/ml, the extract of these vegetables was able to quench 13.2-88.5% DPPH(?) radical in 30 min. The ORAC value ranged from 2.5 to 100.7 μmoles of trolox equivalents per gram of dried sample. The antioxidant capacity of the vegetable samples was highly related to their total phenolic content. The results suggest that these indigenous vegetables consumed by African Americans in the southeastern United States are good sources of the phenolic compounds, which might provide anti-oxidative protection against free radicals in the human body. Consumption of these vegetables might reduce the risk of chronic diseases.     

Antioxidant properties of palm fruit extracts

Phenolic compounds have been shown to exhibit bioactive properties, and in particular antioxidant effects. A phenolic-rich fraction has been isolated from the aqueous by-product obtained during the milling of oil palm fruits. The objectives of the study were to determine the phenolic content of the crude and ethanolic extracts of oil palm fruits and to evaluate the antioxidant properties of these extracts. The total phenolics content of the crude and ethanol extracts as determined by the Folin-Ciocalteu method were found to be 40.3 +/- 0.5 and 49.6 +/- 0.6 mg GAE/g extract (dry basis), respectively. The radical scavenging activity of the extracts determined using 2,2 diphenyl-1-picrylhydrazyl radical (DPPH.) indicated that both crude and ethanol extracts exhibit hydrogen-donating capacity, and have antiradical power (ARP) comparable to ascorbic acid. The DPPH radical scavenging activity of the extracts were less than that of gallic acid, but the time-course variations of the scavenging curves suggest that the extracts acted by a mechanism similar to that of gallic acid. The electron-donating potentials of the extracts were inferred from the hydrogen peroxide scavenging and reducing power assays. The reducing power of crude and ethanol extracts at 1 mM GAE were found to be comparable to that of 0.3 mM gallic acid. The extracts indicated complete scavenging of hydrogen peroxide at concentrations above 0.4 mM GAE. These findings suggest that the crude and ethanol extracts are able to scavenge free radicals, by either hydrogen or electron donating mechanisms, and can therefore act as primary antioxidants.     

Antihepatotoxic nature of Ulva reticulata (Chlorophyceae) on acetaminophen-induced hepatoxicity in experimental rats

Ulva reticulata, a marine edible green alga, is a known source of proteins, vitamins, and sulfated polysaccharides. Though there are many reports in the literature regarding the composition and antiviral property of Ulva sp., studies of the antihepatotoxic property of green seaweeds in animal model are scarce. We have studied the antihepatotoxic nature of this marine green edible alga, U. reticulata, in a hot water extract (150 mg/kg of body weight for a period of 15 days) against acetaminophen- induced hepatotoxicity in experimental albino rats. The acetaminophen-induced rats showed significant elevation in levels of the serum marker enzymes aspartate transaminase and alanine transaminase and of lipid peroxides in liver tissue with decreased levels of antioxidant enzymes such as superoxide dismutase and catalase. The levels of reduced glutathione and vitamins (E and C) were also decreased in the liver tissue of acetaminophen-intoxicated rats. The oral pretreatment with a hot water extract of U. reticulata reduced the hepatotoxicity triggered by acetaminophen considerably by improving the antioxidant status in experimental animals with depleted levels of lipid peroxides. These results indicate that the oral pretreatment with a hot water extract of U. reticulata in rats is effective in reducing the hepatic oxidative stress via free radical scavenging properties, suggesting an antihepatotoxic activity.     

Total phenolics and antioxidant capacity of indigenous vegetables in the southeast United States: Alabama Collaboration for Cardiovascular Equality Project

Collard greens, mustard greens, kale, okra, green onion, butter beans, butter peas, purple hull peas, rutabagas, and eggplant are frequently consumed by African Americans in the southeast United States. Sweet potato greens and purslane are two novel vegetables in this region. The objective of this study was to analyze total phenolics and antioxidant capacity in these indigenous vegetables. The total phenolic content was analyzed using the Folin–Ciocalteu method and ranged from 7.4 to 53.5 mg gallic acid equivalents per gram of dried sample. The antioxidant capacity was analyzed using the radical DPPH^? scavenging capacity assay and oxygen radical absorbance capacity assay (ORAC). At a concentration of 10.0 mg dried vegetable equivalent/ml, the extract of these vegetables was able to quench 13.2–88.5% DPPH^? radical in 30 min. The ORAC value ranged from 2.5 to 100.7 µmoles of trolox equivalents per gram of dried sample. The antioxidant capacity of the vegetable samples was highly related to their total phenolic content. The results suggest that these indigenous vegetables consumed by African Americans in the southeastern United States are good sources of the phenolic compounds, which might provide anti-oxidative protection against free radicals in the human body. Consumption of these vegetables might reduce the risk of chronic diseases.     

Physicochemical characterization and antioxidant activity of 17 commercial Moroccan honeys

In this study, 17 commercial honey samples from Morocco were analyzed. Four samples did not meet the international physicochemical standards due to high hydroxymethylfurfural content and low diastase activity. Phenol content varied from 163.82?mg gallic acid equivalent (GAE)/kg in citrus honey to 923.70?mg (GAE)/kg in thyme honey from Rachidia; flavonoid content ranged from 4.26?mg quercetin equivalent (QE)/kg in citrus honey to 139.62?mg QE/kg in black cumin honey. Black cumin honey had the highest peroxyl scavenging activity; oregano (from Zaraphyt) and thyme honeys (from Rachidia) had the highest ABTS (2,2′-azino-bis[3-ethylbenzothiazoline-6-sulphonic acid]) scavenging activity; and thyme honey (Saouira) had the highest NO scavenging capacity. The antioxidant activity of Moroccan honeys was correlated with the phenol, flavonoid, and melanoidin contents. Dark honeys had higher antioxidant activity than light honeys. Samples with high sodium levels had lower free radical scavenging activity. On the other hand, calcium and magnesium increased the ABTS and peroxyl scavenging capacity, respectively, of honey samples. According to cluster and discriminant analyses, the honey samples were grouped in three clusters with respect to the phenol, flavonoid, melanoidin, proline, mineral and sugar contents, and free radical scavenging capacity.     

Tropical green leafy vegetables prevent garlic-induced hepatotoxicity in the rat

Garlic (Allium sativum) is popularly consumed because of its role in the treatment and management of several diseases. However, unregulated and chronic intake of garlic can cause damage to cells through the production of free radicals. This study was carried out in order to assess the ability of some tropical green leafy vegetables (Telfairia occidentalis, Solanum macrocapon, Corchorus olitorius, Baselia alba, Cnidoscolus acontifolus, Amarantus cruentus, and Ocimum gratissimum) to prevent garlic-induced hepatotoxicity in rats. Wistar strain albino rats were fed diet containing 4% garlic along with or without 40% green leafy vegetable supplement for 14 days. Thereafter, the feeding trial was terminated, the serum of the blood was prepared, and the liver, spleen, intestine, and organ were isolated for gross pathological investigation. The results of the study revealed that there was a significant increase (P < .05) in serum glutamate-oxaloacetate transaminase (SGOT) and glutamate-pyruvate transaminase (SGPT) of the albino rats fed diet containing 4% garlic supplement when compared with the rats fed the basal diet without garlic and vegetable (40%) supplement. However, there was a significant decrease (P < .05) in the serum total protein and albumin levels in those rats. Conversely, there was a consistent significant decrease (P < .05) in the SGOT and SGPT of the rats fed diet containing garlic (4%) and T. occidentalis (40%) and C. acontifolus (40%) supplement compared with those rats fed diet containing garlic (4%) supplement, while there were no consistent significant decrease in those rats fed diet with garlic (4%) alongside with 40% of other leafy vegetables (S. macrocanum, C. olitorius, B. alba, A. cruentus, and O. gratissimum). An increase in serum level of total protein and albumin was also observed in the rats fed T. occidentalis and C. acontifolus. Thus, T. occidentalis and C. acontifolus proved to be better vegetables in preventing garlic-induced hepatotoxicity compared with the other vegetables used in this study.     

Phylloquinone as a biochemical marker for the dietary intake of green leafy vegetables by the K'ekchi people of Alta Verapaz,Guatemala

Vitamin K₁ (phylloquinone) was examined as a potential biochemical marker of indigenous leafy green vegetable intake. Phylloquinone content for 13 species of indigenous leafy green vegetables currently consumed by the K'ekchi‐speaking people of Alta Verapaz, Guatemala, ranged from 0.20–1.14 mg/100 g fresh weight for raw samples (n = 25), and from 0.27–1.51 mg/100 g fresh weight for cooked samples (n = 14) as determined by reversed‐phase high‐performance liquid chromatog‐raphy. Fasting plasma phylloquinone concentrations in a sample of K'ekchi‐speaking women (n = 26) who participated in a dietary survey that estimated the frequency of intake of leafy green vegetables ranged from 0.19–2.01 nmol/L (x = 0.79 nmol/L). When ranked plasma phylloquinone values were compared to the ranked average 7‐day intake of indigenous greens, there was no correlation between the two ranks (p = 0.2157).