Bitter Orange Peel comes from Seville orange and sour orange which grow on trees originally native to Asia and the Mediterranean but now it is grown in warmer places like California and Hawaii (1). It has been used for centuries as a medicinal supplement for digestive system issues, but it also contains an alkaloid called synephrine which has been used and proven effective in multiple weight loss studies (1). 

1. Rohmann, Riana. “Bitter Orange for Weight Loss.” LIVESTRONG.COM, Leaf Group, www.livestrong.com/article/279652-bitter-orange-for-weight-loss/.