Bipolar is a sodium shift in the brain neurons, not a neurotransmitter imbalance. So most standard antidepressants, including natural ones will not work. The reason lithium is used is because it is more reactive than sodium. Potassium is also more reactive, but high doses can lead to heart arrhythmias or stoppage. So lithium is used instead, which just destroys the liver.
A few recommendations:
Magnesium malate 300mg twice daily. DO NOT take it with calcium.
TMG (Trimethylglycine) 1000mg 3 times daily.
GABA (gamma amino butyric acid) 750-1000mg 3 times daily on an empty stomach at least 30 minutes before meals.