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. [1]
Antioxidant activities of carotenes and xanthophylls
The purpose of this study was to assess the relative antioxidant activities of a range of carotenes and xanthophylls through the extent of their abilities to scavenge the ABTS·+ radical cation. The results show that the relative abilities of the carotenoids to scavenge the ABTS·+ radical cation are influenced by the presence of functional groups with increasing polarities, such as carbonyl and hydroxyl groups, in the terminal rings, as well as by the number of conjugated double bonds. [2]
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. [3]
Anti-collagenase, Anti-elastase and Antioxidant Activities of Pueraria candollei var. mirifica root Extract and Coccinia grandis Fruit Juice Extract: An In vitro study
Aims: To determine the in vitro anti-elastase, anti-collagenase and antioxidant properties of two Asian herbs: Pueraria candollei Graham ex Benth. var. mirifica and Coccinia grandis (L.) Voigt that were selected for their anti-aging properties according to their ethnobotanical and chemotaxonomic information.
Place and Duration of Study: School of Agriculture, Food and Rural Development, Newcastle University, United Kingdom, between June and August 2014.
Methodology: The methanolic extract of the roots of P. candolleivar. mirifica (PMM) and the fruit juice extract of C. grandis (CGJ) were investigated by in vitro enzymatic assays to mimic the breakdown of elastin and collagen fibres. Total phenolic content was determined using the Folin-Ciocalteu method (gallic acid equivalent, GAE), while antioxidant capacity was determined as Trolox equivalents (TE) by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging assays.
Results: PMM significantly inhibited elastase activity with IC50 of 143.0±4.78 µg/mL, and its anti-collagenase activity was comparable with that of the positive control, epigallocatechin gallate (EGCG). Based on the same concentration, the elastase inhibitory activity of PMM was significantly higher compared with that of CGJ (P< .001), while the collagenase inhibitory activities of both extracts were comparable. Total phenolic content, DPPH and ABTS radical scavenging activities of 1.0 g equivalent of the dried roots of PMM were 0.6±0.04 mg of GAE, 16.4±6.20 and 9.3±1.38 µmole TE respectively. The antioxidant values of PMM were significantly higher compared with those of 1000 µg/mL of CGJ (GAE, P< .0001; DPPH radical scavenging activity, P< .05; ABTS radical scavenging activity, P< .001). The free radical scavenging activities of both plant extracts were positively correlated with their total GAE (P < .0001).
Conclusion: PMM may play a role in decelerating the skin ageing process and could be formulated for anti-wrinkle skincare products. Further research is required to examine anti-elastase, anti-collagenase and antioxidant activities of individual compounds contained in the roots of PMM and expand the investigation into such anti-ageing effects of the whole fruits of C. grandis, which might contain higher amounts of phytochemicals than the fruit juice. [4]
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. [5]
Reference
[1] Rice-evans, C.A., Miller, N.J., Bolwell, P.G., Bramley, P.M. and Pridham, J.B., 1995. The relative antioxidant activities of plant-derived polyphenolic flavonoids. Free radical research, 22(4), pp.375-383.
[2] Miller, N.J., Sampson, J., Candeias, L.P., Bramley, P.M. and Rice-Evans, C.A., 1996. Antioxidant activities of carotenes and xanthophylls. FEBS letters, 384(3), pp.240-242.
[3] Sun, T. and Ho, C.T., 2005. Antioxidant activities of buckwheat extracts. Food chemistry, 90(4), pp.743-749.
[4] Chattuwatthana, T. and Okello, E. (2014) “Anti-collagenase, Anti-elastase and Antioxidant Activities of Pueraria candollei var. mirifica root Extract and Coccinia grandis Fruit Juice Extract: An In vitro study”, European Journal of Medicinal Plants, 5(4), pp. 318-327. doi: 10.9734/EJMP/2015/14129.
[5] Bouyahya, A., Bakri, Y., Touys, A. E.-, Khouchlaa, A., Idrissi, A. E., 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, 18(4), pp. 1-10. doi: 10.9734/MRJI/2017/30073.
