Caffeine in Citrus flowers

The allocation of purine alkaloids within citrus flowers was studied and fo und to be linked to anthesis, with 99% of the total flower caffeine confine d to the androecium. The main alkaloid is caffeine accompanied by considera ble (up to 30% of caffeine) concentrations of theophylline. In the anther, these purine alkaloids reach altogether a concentration of 0.9% dry wt whic h is close to the caffeine content of the Arabica coffee bean. The pollen a lkaloid concentration is in the same range. Much lower but still marked con centrations were found in the nectar. A considerable breakdown of alkaloids during honey production is assumed. The biological significance of this pa rticular secondary compound allocation as well as possible effects on the k ey pollinator, the honey-bee, are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.