Comparison of phenolic content and antioxidant activity for fermented and unfermented rooibos samples extracted with water and methanol
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Date
2022
Journal Title
Journal ISSN
Volume Title
Publisher
MPDI
Abstract
Rooibos is brewed from the medicinal plant Aspalathus linearis. It has a well-established
wide spectrum of bio-activity properties, which in part may be attributed to the phenolic antioxidant
power. The antioxidant capacity (AOC) of rooibos is related to its total phenolic content (TPC).
The relation between TPC and AOC of randomly selected 51 fermented (FR) and 47 unfermented
(UFR) rooibos samples was studied after extraction using water and methanol separately. The
resulted extracts were assessed using two antioxidant assays, trolox equivalent antioxidant capacity
(TEAC) and ferric reducing antioxidant power (FRAP). The results were analyzed using both simple
statistical methods and machine learning. The analysis showed different trends of TPC and AOC
correlations of FR and UFR samples, depending on the solvent used for extraction. The results of the
water extracts showed similar TPC and higher AOC of FR than UFR samples, while the methanolic
extracted samples showed higher TPC and AOC of UFR than FR. As a result, the methanolic extracts
showed better agreement between TPC and AOC than water extracts.
Description
Keywords
Rooibos tea, Aspalathus linearis, Antioxidant, Water extract, Phenolics
Citation
Hussein, E. A. et al. (2022). Comparison of phenolic content and antioxidant activity for fermented and unfermented rooibos samples extracted with water and methanol. Plants, 11,16. https://doi.org/ 10.3390/plants11010016