Please use this identifier to cite or link to this item:
DC FieldValueLanguage
dc.contributor.authorHussein, Eslam A.en_US
dc.contributor.authorThron, Christopheren_US
dc.contributor.authorGhaziasgar, Mehrdaden_US
dc.contributor.authorVaccari, Mattiaen_US
dc.contributor.authorMarnewick, Jeanine Len_US
dc.contributor.authorHussein, Ahmed A.en_US
dc.identifier.citationHussein, E. A., Thron, C., Ghaziasgar, M. et al. 2022. Comparison of phenolic content and antioxidant activity for fermented and unfermented rooibos samples extracted with water and methanol. Plants, 11: 16. [ 10.3390/plants11010016]en_US
dc.description.abstractRooibos 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. Possible explanations are given for these observed results. Although, the current literature demonstrates direct correlations of the TPC and AOC of rooibos water extracts. This study showed deviation and highlighted the importance of solvent selection and analysis methodology as an important factor in determining the TPC/AOC correlation and subsequently the expectation of the actual health benefits of rooibos herbal tea. In particular, unfermented and fermented samples can be accurately identified on the basis of a combination of assays (any two of TPC, FRAP and TEAC), especially if methanol is the solvent used. Machine learning analysis of assay data provides nearly identical results with classical statistical analytical methods. This is the first report on machine learning analysis and comparison of the TPC and AOC of rooibos herbal tea extracted with methanol and water, and highlights the importance of using methanol as a solvent to evaluate its AOC.en_US
dc.subjectRooibos teaen_US
dc.subjectAspalathus linearisen_US
dc.subjectsmall dataen_US
dc.subjectmachine learningen_US
dc.subjectwater extracten_US
dc.subjectmethanol extracten_US
dc.subjectuncertainty quantificationen_US
dc.titleComparison of phenolic content and antioxidant activity for fermented and unfermented rooibos samples extracted with water and methanolen_US
dc.identifier.doi 10.3390/plants11010016-
Appears in Collections:Appsc - Journal Articles (DHET subsidised)
Files in This Item:
File Description SizeFormat 
Comparison_of_phenolic_content_and_antioxidant.pdfArticle682.76 kBAdobe PDFView/Open
Show simple item record

Google ScholarTM



Items in Digital Knowledge are protected by copyright, with all rights reserved, unless otherwise indicated.