Allelopathic effects of paraxanthine on some phytochemical parameters of Lettuce

Paraxanthine is classified as secondary metabolites derived from purine nucleotides with molecular formula of C7H8N4O2. It occur in green tea, coffee, cocoa and a number of other plant. In this article, the effect of different concentration of paraxanthine was studied on lettuce plant (Lactuca Sativa cv. Siahoo ) as a model plant. In order to show the effect paraxanthine on amount of free amino acids, content sugar, anthocyanines, flavonoides, tannins, alkaloids and phenolic compounds some experiments were performed in a completely randomized design. The lettuce seedlings were cultured in pots containing peat and were irrigated with hoagland nutrient solution containing paraxanthine (with the concentration of 10, 50 and 100µg/ml). three replicated were maintained for each treatment and also for control groups. After of twenty eight days of applying the treatments, the plants were harvested for performing the experiments. Amount of anthosyanines, flavonoid, alkaloids, tannins and phenolic compounds in treated plants were increased compared to the control. the content sugar and total free amino in treated plants were increased compared to the control group. It could be concluded that paraxanthine found in dregs of tea, coffee and cocoa, can be used as a food supplement in the culture of lettuce. Therefore, it increases effective compounds and medicinal benefits of this plant.