Sichuan pepper or Szechuan pepper is a common spice used in Asian cuisine. The plant belongs to the rue or citrus family, which is not closely related to either black pepper or chili peppers, despite its name.
Sichuan pepper has a unique aroma and flavour that is not hot or pungent like black, white or chili peppers. Instead, it has slight lemony overtones and creates a tingly numbness in the mouth (caused by its 3% of hydroxy-alpha-sanshool) that sets the stage for hot spices. According to Harold McGee in On Food and Cooking, second edition, p429 they are not simply pungent; "they produce a strange, tingling, buzzing, numbing sensation that is something like the effect of carbonated drinks or of a mild electrical current (touching the terminals of a nine-volt battery to the tongue). Sanshools appear to act on several different kinds of nerve endings at once, induce sensitivity to touch and cold in nerves that are ordinarily nonsensitive, and so perhaps cause a kind of general neurological confusion." [Source: Wikipedia]
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