In the intervention phase we will administer 500 mg luteolin (2x250 mg capsules, e.g. every morning and evening) per day formulated for oral administration for 14.5 days.

Placebo control intervention consists of identical looking placebo capsules containing mannitol formulated for oral administration to be taken twice daily (e.g. every morning and evening) for 14.5 days.

Luteolin extracted from Chrysanthemum Ramat 98% HPLC by Scyherb® food grade certified according to Safe Quality Foods (SQF) - Level 3 Comprehensive Food Safety and Quality Management System Certification by the Safe Quality Food Institute (SQFI).

Performance in a visual memory test (Rey-Osterrieth complex figure test (Rey 1941) and (Osterrieth 1944)). As parallel version we will use the modified complex Taylor figure test (Hubley 2002).

Participants will have to copy the complex figure. After a short delay of 5 minutes, they will be asked to redraw the figure from memory. A long-delayed recall test will be administered 2 weeks after the learning phase.

Performance is calculated by scoring for accuracy and relative position of the 18 units in the whole of the design. Maximal score is 36 points.

Verbal memory task (de Quervain, Roozendaal et al. 2000). A parallel version will be used for the second study phase.

Subjects are given explicit instructions to learn 60 unrelated German nouns for immediate and delayed recall. For all free-recall tests (immediate recall, short delay and long delay), subjects will be asked to write down all the words they remember. The number of correctly recalled words (hits) will be the relevant output.

Delayed recall of all 60 words will be tested about 10 min (short delay) and 2 weeks (long delay) after presentation.