Cancer has emerged as an important health problem in the developed and the developing countries. In the present investigation, 12 medicinal plants were evaluated against human cancer cell lines from different origins and most significant results were displayed by Apium graveolens, Holarrhena antidysenterica, Mallotus philippinensis and Nardostachys jatamansi. Further, an active ingredient namely Mallotoxin was isolated from the fruit part of Mallotus philippinensis. This drug suppressed the proliferation of eight human cancer cells from six different tissues and proved its exceptionally remarkable in vitro anticancer efficiency.