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The influence of the extraction time on the amounts of umbelliferone derivatives in methanolic (a), methanol/water (75/25 v/v; b), methanol/water (50/50 v/v; c), methanol/water (25/75 v/v; d), methanol/phosphoric buffer (pH 5; 75/25 v/v; e), methanol/phosphoric buffer (pH 9; 75/25 v/v; f) extracts from chamomile, all heated under reflux. Numbers under bars correspond to compound numbers reported in Supplementary Scheme 1
