Pepper owes its properties to an alkaloid, piperine, and to a volatile oil.
"Human Foods and Their Nutritive Value"
Harry Snyder
In the black pepper berries there is present ash to the extent of about 4.5 per cent, it ought not to be above 6.5 per cent; ether extract, including piperine and resin, not less than 6.5 per cent; crude fiber not more than 16 per cent; also some starch and nitrogenous material.
"Human Foods and Their Nutritive Value"
Harry Snyder