S. Rezai Erami; S.M. Jafari; M. Khomeiri; H. Bayat
Abstract
Recently, there is an increasing trend to use natural antioxidants due to undesirable effects of synthetic antioxidants. In this study, phenolic compounds of shahmirzadi variety of walnut leaf were extracted with traditional and microwave assisted extraction (MAE) methods. In traditional method, extraction ...
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Recently, there is an increasing trend to use natural antioxidants due to undesirable effects of synthetic antioxidants. In this study, phenolic compounds of shahmirzadi variety of walnut leaf were extracted with traditional and microwave assisted extraction (MAE) methods. In traditional method, extraction was performed with methanol 80%, ethanol 50% , boiling water and water at ambient temperature (6, 12, 18 and 24 hours) and in MAE it was done with methanol 80%, ethanol 50% (2, 4. 6 and 8 minutes) and boiling water (3, 6 and 9 minutes). Total phenolic content was determined by Folin-Ciocaltue reagent. In MAE, methanol extract of walnut leaf had the highest total phenolics with 130.16±0.19 mg/g. The antioxidant capacity of extracts was assessed through reducing power assay, DPPH radical-scavenging activity and total antioxidant activity. Extracts showed antioxidant activity in a concentration-dependent way. The ethanol extract of leaves in the reducing power assay and DPPH radical-scavenging activity and the methanol extract of leaves in the antioxidant activity assay presented the highest antioxidant activity. Finally, the influence of methanol extract in retarding the soy bean oxidation was examined. Our results showed that extracts could prevent formation of initial and secondary products of oxidation and an extract with 1000 ppm phenolic content could control oxidation of oil. Hence we can present shahmirzadi walnut leaves as a potential source of natural antioxidants.
Z. Rafiei; S.M. Jafari; M. Alami; M. Khomeiri
Abstract
The aim of the study was to investigate the effect of extraction through two methods of maceration and microwave-assisted extraction on phenolic compounds of olive leaves (Mishen cultivar) with solvents of water, 80% methanol and acetone. The highest total phenolic content (211.385±0.13 mg tannic ...
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The aim of the study was to investigate the effect of extraction through two methods of maceration and microwave-assisted extraction on phenolic compounds of olive leaves (Mishen cultivar) with solvents of water, 80% methanol and acetone. The highest total phenolic content (211.385±0.13 mg tannic acid/g extract) was related to the methanol extract produced by microwave-assisted extraction but acetone extracts gave the lowest amount for both methods. Comparing the extraction methods showed that MAE had higher extraction efficiency in all three tested solvents. Regarding antimicrobial activity of olive leaf extracts, we evaluated the bactericidal effects of different solvent extracts on Staphilococcus aureus, Salmonella typhi and Escherishia coli. In terms of S. aureus, the lowest minimum inhibitory concentration (MIC= 315 µg/ml) and. minimum bactericidal concentration (MBC= 2500 µg/ml) were observed with acetone extract in MAE and methanol extracts in both methods, respectively. As for E.coli the lowest MIC was 625 µg/ml and the lowest MBC (5000 µg/ml) was associated with water and methanol extracts in microwave-assisted extraction. In terms of S. typhi, the lowest MIC and MBC were 315 and 10000 µg/ml, respectively. To conclude, it was found that S. typhi was the most resistant bacteria against the extracts; in most cases MAE-produced extracts showed more antimicrobial activity compared to traditional-produced extracts.
