Guarana

Guarana is a stimulating tonic that is believed to improve physical stamina and endurance. Because its guaranine content is almost identical to caffeine in its actions, athletes have been known to take it to stimulate and improve their performance and increase their strength and endurance. It is also thought to reduce fatigue and exhaustion. The combination of guarinine, theobromine and theophyline act to stimulate the central nervous system and also act to enhance the metabolic rate, which may be helpful in weight loss programs. 
As a "nervine," Guarana is also said to strengthen functional activity of the nervous system. The alkaloids, theobromine, and theophylline act to stimulate the central nervous system and are thought to be useful in cases of neuralgia, paralysis, migraine and nervous headache (particularly popular in the U.S. and Europe) and the distress that sometimes accompanies menstruation.

Guarana is considered a gentle excitant that is said to be good for depression and mental exertion where there is fatigue or even exhaustion from hot weather. It is also thought to increase mental sharpness and concentration, which may also be a result of its guarinine content.

The tannins in Guarana act as an astringent and are said to help ease mild forms of leucorrhoea (vaginal discharge) and diarrhea.

As a mild diuretic, Guarana is thought to promote urine flow and act as febrifuge that helps to reduce mild fevers. It is also said to alleviate urinary tract irritation.