Journal
MOLECULES
Volume 27, Issue 11, Pages -Publisher
MDPI
DOI: 10.3390/molecules27113556
Keywords
green rooibos; beta-cyclodextrin extraction; antioxidant activity; polyphenolic content; encapsulation
Funding
- National Research foundation (NRF) Black Academics Advancement Programme (BAAP) [120639]
- Cape Peninsula University of Technology International-PICT 2012 Argentina-South Africa ASACEN [3070]
- Argentine-South African Nanotechnology Center-National Research Foundation, Department of Science & Technology, Pretoria, South Africa
- Agencia Nacional de Promocion Cientifica y Tecnologica [PICT 2013-1331]
- Centro Argentino-Sudafricano en Nanotecnologia [PICT-ASACEN 2012-3070]
- Universidad de Buenos Aires [UBACYT 20020170100459BA]
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This study optimized the beta-cyclodextrin-assisted extraction of crude green rooibos, finding that the optimal conditions were 15 mM beta-CD: 40 degrees C: 60 min, resulting in high polyphenolic content and antioxidant activity. Aspalathin, hyperoside, and orientin were identified as the major active compounds.
Antioxidant activity associated with green rooibos infusions is attributed to the activity of polyphenols, particularly aspalathin and nothofagin. This study aimed to optimise beta-cyclodextrin (beta-CD)-assisted extraction of crude green rooibos (CGRE) via total polyphenolic content (TPC) and antioxidant activity assays. Response surface methodology (RSM) permitted optimisation of beta-CD concentration (0-15 mM), temperature (40-90 degrees C) and time (15-60 min). Optimal extraction conditions were: 15 mM beta-CD: 40 degrees C: 60 min with a desirability of 0.985 yielding TPC of 398.25 mg GAE.g(-1), metal chelation (MTC) of 93%, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging of 1689.7 p.mol TE.g(-1), ferric reducing antioxidant power (FRAP) of 2097.53 p.mol AAE.g(-1) and oxygen radical absorbance capacity (ORAC) of 11,162.82 TE.g(-1). Aspalathin, hyperoside and orientin were the major flavonoids, with quercetin, luteolin and chrysoeriol detected in trace quantities. Differences (p < 0.05) between aqueous and 13-CD assisted CGRE was only observed for aspalathin reporting the highest content of 172.25 mg.g(-1) of dry matter for extracts produced at optimal extraction conditions. Positive, strong correlations between TPC and antioxidant assays were observed and exhibited regression coefficient (R-2) between 0.929-0.978 at p < 0.001. These results demonstrated the capacity of beta-CD in increasing polyphenol content of green rooibos.
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