Awraris Derbie Assefa

Metabolite profiling of green, green/red, and red lettuce cultivars: Variation in health beneficial compounds and antioxidant potential

Salad vegetables, commonly consumed at baby-leaf stages, are the most appropriate and emerging dietary source of antioxidant compounds. Screening and identification of nutrient-rich cultivars can be potentially useful to obtain a nutrient-dense diet. Thus, in this study, we explored the genetic potential of baby leaves of 23 diverse lettuce cultivars for the health-beneficial metabolites. The results showed that the composition and contents of the studied metabolites in lettuces varied significantly between cultivars and were principally dependent on leaf color. All red-leaf cultivars were rich in carotenoids, cyanidin, polyunsaturated fatty acids (PUFAs, primarily in the form of α-linolenic and linoleic acid,) total phenolic contents (TPC), and antioxidant potential. Among carotenoids, all-E-lutein was found in highest amount, followed by all-E-violaxanthin and all-E-lactucaxanthin, accounting for an average of 30%, 28% and 15% of total carotenoids, respectively. The content of total folate was recorded in the range of 6.51 (cv. Caesar Green) to 9.73μg/g (DW) (cv. Asia Heuk Romaine). The principal component analysis (PCA) showed that the cyanidin and other phenolic compounds are the most potent scavengers of ABTS and DPPH radicals. The overall results suggested that all red-leaf lettuce cultivars have a distinct profile of phytoconstituents, which can be used as a nutrient-dense food.

Comparison of Flavonoid Contents and Antioxidant Activity of Yuzu (Citrus junos Sieb. ex Tanaka) Based on Harvest Time

The aim of this study was to evaluate the changes of fruit quality, flavonoid contents and antioxidant activity of Yuzu (Citrus junos Sieb. ex Tanaka) from Go-heung and Jeju according to harvest time. Samples were harvested from August to December on the 1 st of every month. August and September samples were green colored, whereas November and December samples were yellow. The fruit shape index decreased, changing from globular to elliptical, whereas the °birx increased with ripening stage. The yuzu from Jeju was larger than that from Go-heung in each month of cultivation. August samples exhibited the highest amounts of phenolic compounds. In addition, samples from Jeju had higher total phenolic content than those from Go-heung. The content of phenolic compounds decreased with ripening until October and then increased subsequently. Antioxidant activity of the yuzu was evaluated by FRAP and DPPH methods. The antioxidant activity showed a similar trend as total phenolic content. Immature yuzu fruit was found to exhibit the highest amount of flavonoids such as naringin and hesperidin. November and December samples showed almost the same contents of flavonoids. The flavonoid content of yuzu fruit harvested from Jeju was higher than that from Go-heung. Overall, the samples harvested at the early stage, in the month of August, exhibited the highest flavonoid content, phenolic content and antioxidant activity. As the health benefits of these compounds has been demonstrated in various studies, the immature yuzu appears to be preferable for use as a raw material for formulation of pharmaceutical products as well as for functional food production after a proper in-vivo and in-vitro medical tests.

A comparative study of anaerobic and aerobic decomposition of quercetin glucosides and sugars in onion at an ambient temperature

The purpose of the study was to investigate the decomposition of onions under anaerobic and aerobic conditions. The main aim was to determine the changes in composition of quercetin-related compounds and sugars, with simultaneous analysis of total phenolics, total flavonoids and antioxidant activity. The results indicate that anaerobic conditions lead to the deterioration of onions, along with a gradual decrease in quercetin glucoside content. However, the quercetin aglycone increased simultaneously to 0.64 µmol g−1 fresh weight (FW) during the 10th week, while the fresh onions contained 0.06 µmol g−1 FW. The total sugar content decreased incessantly, while the total phenolics and flavonoids increased to 7080.67 ± 1248.20 µg gallic acid equivalents g−1 FW and 2340.10 ± 203.47 µg quercetin equivalents g−1 FW, respectively, during the 10th week. Under the aerobic condition, the total quercetin content was found to increase slowly but had a tendency to decrease during storage. The sugar content increased up to 6 weeks, followed by its gradual decrease. In addition, the total phenolics, flavonoids and antioxidant activity exhibited a decline during 1 month, with their highest content being observed during the 8th week.

Extraction of Antioxidants from Aloe vera Leaf Gel: a Response Surface Methodology Study

Extraction of antioxidants from aloe gel powder with water–ethanol solvents was studied using response surface methodology. The independent variables were solvent composition, temperature, extraction time, and the liquid-to-solid (L/S) ratio. The concentrations of potentially antioxidant compounds (aloin A and B, aloesin, total phenolics, and total carbohydrates) and a few indicators of antioxidant capacity (DPPH, FRAP, CUPRAC) served as the response functions. It was found that aloe gel contains both phenolic and non-phenolic antioxidants, and it was supposed that the phenolic fraction consists almost exclusively of chromones and anthrones. Different approaches to the optimization of extraction procedures are discussed, and here, the maximum recovery yield of antioxidants is achieved with 34 % ethanol at 60 °С and a L/S ratio of 46 in 1 h. The use of 90 % ethanol results in a higher antioxidant capacity of the product, but also results in a much lower extraction yield, decreasing the overall productivity of the process.

Effect of extraction solvent and various drying methods on polyphenol content and antioxidant activities of yuzu (Citrus junos Sieb ex Tanaka)

The effects of different extraction solvents (water, EtOH, MeOH, acetone, DMSO, and their mixture) and various drying methods (air, oven, microwave, and freeze drying) were investigated on total polyphenol content (TPC), total flavonoid content (TFC) and antioxidant activity of peel, pulp, and seeds of yuzu fruit. Mixed solvents exhibited better results compared to the absolute solvents. 50 % acetone exhibited the highest FRAP and CUPRAC value in peel and pulp and TPC in seeds of yuzu fruits. 80 % acetone which also gave nearly similar results with 50 % acetone (p > 0.05) showed the highest TPC in peels and pulp and highest CUPRAC values in seeds. Absolute acetone was the least desirable solvent employed for extraction in most of the samples. Drying methods also significantly affected the total polyphenols content, total flavonoid content and antioxidant potential of yuzu fruits. Oven drying resulted in declines of the TPC, TFC, FRAP, DPPH, and CUPRAC from 0.2 to 33.0 % relative to fresh samples while air drying resulted a decrease in the range between 2.5 and 30.6 %. Freeze dried samples showed the highest percent retentions of polyphenols content, flavonoid content, and antioxidants (70.6–122.1 %). Drying methods caused the highest loss of TPC, TFC, FRAP, and CUPRAC in pulp samples except DPPH radical scavenging activity. In overall, the extraction of secondary metabolites and antioxidants was highly dependent on the extraction solvent, type of sample and sample processing methods.

Assessing phenolic content and antioxidant potential diversity in Allium plants using multivariate data analysis

The genus Allium includes hundreds of plant species and is regarded as one of the most cultivated vegetables. It is an important source of novel therapeutic compounds known for their beneficial effects on human health; however, there could be differences in content, composition, type, and bioactivity of the phytochemicals found among the Allium plants. The main purpose of this study was to acquire insights on the variation in antioxidant profiles and phenolic content between Allium accessions in different species, as well as between similar species of several varieties. We collected 112 accessions from more than 20 countries, and grew them under similar agronomic conditions. The antioxidant potential was evaluated by using 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS), 1,1-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and reducing power (RP) assays. The total phenolic content (TPC) was studied using the Folin–Ciocalteu method. TPC varied from 3.43 (accession 199897) to 22.19 (accession 273483) µg gallic acid equivalent/mg dry weight (DW) of the aerial organs of Allium. The antioxidant activity of Allium samples ranged from 4.37 (accession 806595) to 57.46 (accession number 711971) µg Trolox equivalent/mg DW; 0.35 (accession 117246) to 9.53 (accession 711971) µg ascorbic acid equivalents/mg DW; 2.92 (accession 199890) to 21.20 (accession 803493) µgAAE/mg DW; and 0.80 (accession 117260) to 31.13 (accession 803527) µgAAE/mg DW using ABTS, DPPH, FRAP, and RP assays, respectively. Accessions 273483 (A. cepa), 283346 (A. cepa ‘cepa’), and 803527 (unknown species) had the highest TPC, FRAP, and RP values among those tested, while the highest ABTS and DPPH radical scavenging activities were recorded in accession 711971 (A. ramosum). Pearson’s coefficient of correlations indicated that variables (TPC, ABTS, DPPH, FRAP, and RP values) correlated significantly each other, with r-values between 0.585 and 0.894. Principal component analysis plots and hierarchical cluster analysis indicated significant variability in antioxidant activity and phenolic content among all the accessions studied, as well as within similar species. Based on our results from principal component and hierarchical cluster analysis, accession 283346 (A. cepa ‘cepa’), K139348 (A. fistulosum), and 711971 (A. ramosum) are potential sources of phenolics and natural antioxidants. The variability in total phenolic and antioxidant activity among the Allium accessions can be used by breeders, food technologists, nutritionist, and researchers for assessing breeding lines for genetic selection and for monitoring levels of these factors during food storage and processing.