Effects of time and extraction temperature on phenolic composition and functional properties of red rooibos (Aspalathus linearis)

Jânio Sousa Santos; Carolina Turnes Pasini Deolindo; Luis Antônio Esmerino; Maria Inés Genovese; Alice Fujita; Mariza Boscacci Marques; Neiva Deliberali Rosso; Heitor Daguer; Andressa Camargo Valese; Daniel Granato

doi:10.1016/j.foodres.2016.08.041

Effects of time and extraction temperature on phenolic composition and functional properties of red rooibos (Aspalathus linearis)

Food Res Int. 2016 Nov;89(Pt 1):476-487. doi: 10.1016/j.foodres.2016.08.041. Epub 2016 Aug 28.

Affiliations

¹ Food Science and Technology Graduate Program, State University of Ponta Grossa, Av. Carlos Cavalcanti, 4748, 84030-900, Ponta Grossa, Brazil.
² Department of Clinical Analysis, State University of Ponta Grossa, Av. Carlos Cavalcanti, 4748, 84030-900, Ponta Grossa, Brazil.
³ Laboratory of Food Bioactive Compounds, Department of Food and Experimental Nutrition, University of São Paulo, 05508-900, São Paulo, Brazil.
⁴ Department of Chemistry, State University of Ponta Grossa, Av. Carlos Cavalcanti, 4748, 84030-900, Ponta Grossa, Brazil.
⁵ Brazilian Ministry of Agriculture, Livestock and Food Supply (MAPA), National Agricultural Laboratory, 88102-600, Santa Catarina, Brazil.
⁶ Food Science and Technology Graduate Program, State University of Ponta Grossa, Av. Carlos Cavalcanti, 4748, 84030-900, Ponta Grossa, Brazil. Electronic address: dgranato@uepg.br.

PMID: 28460941
DOI: 10.1016/j.foodres.2016.08.041

Abstract

This work was aimed at assessing the time-temperature effects on the phenolic compounds and in vitro functional properties of aqueous extracts from red rooibos (Aspalathus linearis). The major phenolic composition (tannins, flavonoids, flavonols, ortho-diphenols, total phenolic content), antioxidant (ABTS and DPPH) and reducing capacities (FRAP and total reducing capacity), antimicrobial effects and inhibition of α-amylase/α-glucosidase were measured. Phenolic compounds were also determined by LC-ESI-MS/MS. Aqueous extracts did not inhibit the growth of Escherichia coli, Staphylococcus aureus, and Candida albicans between 7.81 and 1000mgL^-1. Rooibos extracted at 85°C for 10min showed a beneficial interaction with the human erythrocytes, reducing the hemolysis. The correlation analysis showed that the phenolic compounds responsible for the inhibition of α-amylase (IC₅₀) were isohrmanetin, isoquercitrin, luteolin, salicylic acid, and syringaldehyde, whereas the inhibition of α-glucosidase was correlated to syringaldehyde, isoquercitrin, and luteolin. Overall, rooibos extracted at 85°C had the highest antioxidant activity measured by all assays, higher contents of phenolic compounds (spectrophotometric and LC-ESI-MS/MS data), and lower IC₅₀ values for the digestive enzymes. On the other hand, rooibos extracted at 65°C had the opposite behavior, while rooibos extracted at 75°C presented mean intermediate values for the responses. This result clearly indicates that the extraction temperature is the main factor leading to a higher extraction of bioactive compounds from red rooibos.

Keywords: Antioxidants; Extraction temperature; Flavonoids; Functional foods; Organic food; Phenolic acids.