Latest Research News on Antioxidant Activities: April 2021
The Relative Antioxidant Activities of Plant-Derived Polyphenolic Flavonoids
The relative antioxidant activities, against radicals generated in the aqueous phase, of a range of plant-derived polyphenolic flavonoids, constituents of fruit, vegetables, tea and wine, have been assessed. The results show that compounds such as quercetin and cyanidin, with 3′,4′ dihydroxy substituents in the B ring and conjugation between the A and B rings, have antioxidant potentials four times that of Trolox, the vitamin E analogue. Removing the ortho-dihydroxy substitution, as in kaempferol, or the potential for electron deloculisation by reducing the 2.3 double bond in the C ring, as in catechin and epicatechin, decreases the antioxidant activity by more than 50%. but these structures are still more effective than α-tocopherol or ascorbate. The relative significance of the positions and extents of hydroxylation of the A and B rings to the total antioxidant activity of these plant polyphenols is demonstrated. 
The Antioxidant Activities of the Some Commercial Teas
The antioxidant activities and their antioxidant compounds of a group of teas obtained in local markets were investigated. A total of 18 teas were tested for their antioxidant activities based on their ability to scavenge ABTS (2,2′-Azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) cation radical and DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical. The former was expressed as mg of ascorbic acid equivalents per 1 tea bag (L-ascorbic acid equivalent antioxidant capacity, AEAC) and the latter was expressed as percentage of electron donating activity (EDA%). A good correlation of AEAC and EDA was observed between the two methods. The concentrations of total polyphenolics and flavonoids in tea extracts were measured by spectrophotometric methods. Total ascorbic acid was determined via the 2,6-dicholoroindophenol titrimetric method. According to the AEAC value and EDA, black tea, brown rice green tea, green tea, herb tea and malva tea showed relatively high antioxidant activities. Polyphenolic compounds were the major naturally occurring antioxidant compounds found in teas and the high concentrations of polyphenolic compounds were observed in black tea, green tea and herb tea. Overall, six teas out of 18 teas tested in the study showed better antioxidant activities and higher amounts of total polyphenolic compounds. 
Antioxidant activities of buckwheat extracts
The antioxidant activities of buckwheat (Fagopyrum esculentum Möench) extracts were evaluated and compared with butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tertiary butylhydroquinone (TBHQ) using a β-carotene bleaching assay, a 2,2-diphenyl-β-picrylhydrazyl (DPPH) assay and the Rancimat method. Buckwheat was extracted with solvents of different polarities. The methanol extract showed the highest antioxidant activity coefficient (AAC) of 627 ± 40.0 at 200 mg/l by the β-carotene bleaching method and longest induction time of 7.0 ± 0.2 h by the Rancimat method. The acetone extract showed the highest total phenolics of 3.4 ± 0.1 g catechin equivalents/100 g and the highest scavenging activity of 78.6 ± 6.2% at 0.1 mg/ml by the DPPH method. The properties of the extracting solvents significantly affected the yield, total phenolics and antioxidant activity of buckwheat extract. 
Effect of Blanching Time on Total Phenolic, Antioxidant Activities and Mineral Content of Selected Green Leafy Vegetables
Effect of blanching time in hot water (0, 5, 10 and 15 min) was carried out on six green leafy vegetables popularly consumed in Nigeria namely; Cnidoscolus asconitifolius, Talinum triangular, Celosia argentea, Amaranthus hybridus, Vernomia anygdalina, and Telfaria occidentalis. The dry matter, total phenolic content, antioxidant activity and mineral content of the green leafy vegetables were analyzed. Blanching at temperature of 90°C and different times decreased the dry matter content of the vegetables; 5 min blanching significantly (p > 0.05) increased the total phenolic (280.6 – 980.6 mgGAE/100 g db) and antioxidant activity (25.1 – 95.1 mg/100 g Trolox equivalent) in all the vegetables. However, further increase in the blanching time caused a significant reduction in total phenolic content, antioxidant activities and mineral content of all the vegetables. With these results, it could be concluded that blanching time for these vegetables should range between 1 to 5 min to prevent the loss of health benefiting compound present in them. 
In vitro Screening of Antibacterial and Antioxidant Activities of Essential Oils from Four Moroccan Medicinal Plants
Aims: Evaluation of antibacterial and antioxidant activities of essential oils extracted from Salvia officinalis, Mentha viridis, Eucalyptus globulus and Myrtus communis from Ouezzane province.
Study Design: In vitro evaluation of antibacterial and antioxidant activities of medicinal plants essential oils (EOs).
Place and Duration of Study: Department of Biology (Faculty of Sciences), July, 2015 to September, 2016 (15 Months).
Methodology: Essential oils were extracted by hydrodistillation method, while agar well diffusion, microdilution and spectrophotometry methods were used to evaluate the antibacterial and antioxidant activities respectively.
Results: The yields of EOs are 0.9, 1.2, 2.5, and 2.1% for M. communis, E. globulus, M. viridis, and S. officinalis respectively. EOs showed significant antibacterial activities against test bacterial strains:Staphylococcus aureus CECT 976, Staphylococcus aureus CECT 994, Listeria monocytogenes serovar 4b CECT 4032, Proteus mirabilis, Staphylococcus aureus MBLA, Escherichia coli K12, Pseudomonas aeruginosa and Bacillus subtilis 6633. Salvia officinalis EO was more active than the rest EOs on the test bacteria and exhibited the highest zone of inhibition (23 mm) against B. subtilis bacterial, while P. aeruginosa was the most resistant bacterial strain. S. officinalis and M. communis EO showed minimum inhibitory concentration at MIC=0.5 % (v/v) against L. monocytogenes and P. mirabilis. The antioxidant results indicated that M. communis and S. officinalis posess the ability to scavenge DPPH radicals. Their IC50 Values of 0.24 and 0.46 mg/mL respectively, suggest their anatioxidant capacity compared to reference drugs IC50value (IC50=0.027 mg/mL for ascorbic acid and IC50=0.043 mg/mL for Trolox).
Conclusion: Our study showed that apart from the local uses of the plants extracts, the EOs of S. officinalis,M. viridis, E. globulus and M. communis plants poses strong antibacterial and antioxidant properties and may be useful as food preservatives. 
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 Choi, Y.M., Kim, M.H., Shin, J.J., Park, J.M. and Lee, J.S., 2003. The antioxidant activities of the some commercial teas. Journal of the Korean Society of Food Science and Nutrition, 32(5), pp.723-727.
 Sun, T. and Ho, C.T., 2005. Antioxidant activities of buckwheat extracts. Food chemistry, 90(4), pp.743-749.
 Bamidele, O.P., Fasogbon, M.B., Adebowale, O.J. and Adeyanju, A.A., 2017. Effect of blanching time on total phenolic, antioxidant activities and mineral content of selected green leafy vegetables. Current Journal of Applied Science and Technology.
 Bouyahya, A., Bakri, Y., Et-Touys, A., Khouchlaa, A., El Idrissi, A.E.Y., Abrini, J. and Dakka, N., 2017. In vitro screening of antibacterial and antioxidant activities of essential oils from four Moroccan medicinal plants. Microbiology Research Journal International, pp.1-10.