Trifoliate Orange, Poncirus trifoliata (syn. Citrus trifoliata), is a member of the family Rutaceae, closely related to Citrus, and sometimes included in that genus, being sufficiently closely related to allow it to be used as a rootstock for Citrus. It differs from Citrus in having deciduous, compound leaves, and pubescent (downy) fruit. It is native to northern China and Korea, and is also known as the Chinese Bitter Orange. Poncirus trifoliata is recognisable by the large 3–5 cm thorns on the shoots, and its deciduous leaves with three (or rarely, five) leaflets, typically with the middle leaflet 3–5 cm long, and the two side leaflets 2–3 cm long. β-Sitosterol and 2-hydroxy-1,2,3-propane tricarboxylic acid 2-methyl ester (HPCME) were isolated and identified from Poncirus trifoliata for the first time. These compounds have been tested for their antioxidant capacity and inhibition of cancer cell proliferation and apoptosis using human colon cancer cell line (HT-29).