For ages, peppermint and its extract (such as peppermint oil) have been used as an herbal remedy for nausea, vomiting, GI cramps, gas, colds, morning sickness, diarrhea, and small intestine bacteria overgrowth (SIBO). That being said, these claims have not been medically proven. What we do know though is that peppermint does have antioxidants and a fairly high amount, judging by its ORAC value.
ORAC Source
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010