The major constituents in St. John’s wort include hypericin and other dianthrones, flavonoids, xanthones, and hyperforin. While it was previously thought the antidepressant actions of St. John’s wort were due to hypericin and the inhibition of the enzyme monoamine oxidase, current research has challenged this belief, focusing on other constituents, such as hyperforin, and flavonoids. Test tube studies suggest that St. John’s wort extracts may exert their antidepressant actions by inhibiting the reuptake of the neurotransmitters serotonin, norepinephrine, and dopamine. This action is possibly due to the constituent hyperforin. St. John’s wort is able to act as an antidepressant, by making more of these neurotransmitters available to the brain.