Emodin is moderately cytotoxic and can inhibit the growth of many cell types by interfering with the cell cycle, possibly by stimulating the expression of p53 and p21. Alternatively, it may do this by creating DNA strand breaks and/or non-covalently binding to DNA and inhibiting the catalytic activity of topoisomerase II. It may also induce apoptosis by inhibiting the electron transport chain, producing reactive oxygen species. Emodin is a strong inhibitor of tyrosine-protein kinase Lck and other tyrosine kinase receptors, which likely contributes to its growth suppressing activity. It may act as a chemopreventive agent by activating DNA repair machinery.

Emodin can also inhibit metastasis by interfering with the activity of matrix metalloproteinases, either directly or through through inhibition of focal adhesion kinase, mitogen-activated protein kinase, and RAC-alpha serine/threonine-protein kinase activation, and partial inhibition of transcription factor AP-1 and nuclear factor NF-kappa-B (NF-kB) transcriptional activities.

Emodin exerts its purgative effects by acting directly or indirectly on colon epithelial cells. This activates the underlying smooth muscle cells, leading to muscle contractility. Possible mechanisms for this effect includes enhancing the hormone motilin, activating muscarinic receptors by triggering the release of acetylcholine, stimulating the protein kinase C-alpha pathway for increased calcium sensibility, inhibiting the secretion of the hormone somatostatin, increasing fluid electrolyte accumulation in the distal ileum and colon, and inhibiting the activity of Na+/K+-ATPase and/or potassium channels. 

Emodin's antiinflammatory action is due to its specific inhibition of the transcription factor NF-kB. It also regulates angiogenesis by inhibiting the enzymes casein kinase II and nitric oxide synthase and has shown potent estrogen receptor binding affinity. Emodin can induce the microsomal enzyme cytochrome P-450 1A1, perpetuating its own metabolic activation. (A3043, A3044, A3045, A3046, A3047, A3048, A3049, A3050, A3051, A3052, A3053, A3054)