title: Occurrence and sensory perception of Z-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic acid in rooibos (Aspalathus linearis).
abstract: Z-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic acid (PPAG), a compound postulated to contribute to the taste and mouthfeel of fermented rooibos tea (Aspalathus linearis), was isolated from unfermented rooibos plant material. Its structure was unequivocally confirmed by LC-MS, -MS(2), FT-IR and NMR of the underivatised natural product, and optical rotation measurements of the hydrolysed sugar moiety. A similar compound, postulated to be E-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic acid, was also detected. Analysis of the leaves of a large number of rooibos plants (n=54), sampled at commercial plantations, showed that PPAG is not ubiquitously present in detectable quantities in the leaves of different plants. This leads to large variation in the fermented plant material, infusions and food-grade extracts. PPAG was shown to have a slightly bitter to astringent taste and a detection threshold of 0.4 mg/l in water.
authors.affiliation: Post-Harvest and Wine Technology Division, Agricultural Research Council (ARC) Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa. joubertl@arc.agric.za
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Joubert
authors.forename: Dalene
authors.initials: D
authors.lastname: de Beer
authors.forename: Christiaan J
authors.initials: CJ
authors.lastname: Malherbe
authors.forename: Nina
authors.initials: N
authors.lastname: Muller
authors.forename: Susan L
authors.initials: SL
authors.lastname: Bonnet
authors.forename: Jan H
authors.initials: JH
authors.lastname: van der Westhuizen
authors.forename: Daneel
authors.initials: D
authors.lastname: Ferreira
mesh_terms: D036903:Aspalathus / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry*; D006801:Humans; D010666:Phenylpropionates; D010936:Plant Extracts / Q000737:chemistry*; D055697:Taste Perception
chemical_list: D005419:Flavonoids; D010666:Phenylpropionates; D010936:Plant Extracts; C019521:phenylpropiolic acid