Potency of extracts from selected Egyptian plants as inducers of the Nrf2-dependent chemopreventive enzyme NQO1.

Medicinal plants from the Egyptian Sinai Peninsula are widely used in traditional Bedouin medicine to treat a range of conditions including cancer, and as such are a promising resource for novel anti-cancer compounds. To achieve scientific justification of traditional use and/or to recommend the use of those plants as medicinal herbs for cancer chemoprevention, a group of 11 Sinai plants of different species that belong to 3 families (Asteraceae, Lamiaceae, and Euphorbiaceae) were biologically screened for cancer preventive activity using the chemoprevention marker enzyme NAD(P)H: quinone oxidoreductase 1 (NQO1). Among the fractions assayed, a solvent extract from Pulicaria incisa had potent NQO1 inducing activity. Further analysis of the mechanism of induction revealed the concentration-dependent stabilization of the transcription factor NF-E2 p45-related factor 2 (Nrf2) and a coordinate upregulation of the Nrf2-dependent enzymes NQO1, heme oxygenase 1 and glutathione S-transferase-Pi. These results establish P. incisa as a promising target for future phytochemical characterization for cancer preventive components.

NAD(P)H : quinone oxidoreductase 1 inducer activity of some Saudi Arabian medicinal plants.

Medicinal plants are a rich source of biologically-active phytochemicals and have been used in traditional medicine for centuries. Specific phytochemicals and extracts of their plant sources have the ability to reduce the risk for chronic degenerative diseases by induction of enzymes involved in xenobiotic metabolism, many of which also have antioxidant and anti-inflammatory functions. One such multifunctional cytoprotective enzyme is NAD(P)H : quinone oxidoreductase. In this study, we prepared extracts of 27 Saudi Arabian medicinal plants which belong to 18 different plant families and tested their ability to induce NAD(P)H : quinone oxidoreductase in murine hepatoma cells grown in microtiter plate wells. In addition to the Brassicaceae, a known source of NAD(P)H : quinone oxidoreductase inducer activity, we found substantial inducer activity in extracts from the Apiaceae, Apocynaceae, and the Asteraceae families. Five out of a total of eight active extracts are from plants which belong to the Asteraceae family. We further show that artemisinin, an agent which is used clinically for the treatment of malaria, contributes but does not fully account for the inducer activity of the extract of Artemisia monosperma. In contrast to artemisinin, deoxyartemisinin is inactive in this assay, demonstrating the critical role of the endoperoxide moiety of artemisinin for inducer activity. Thus, the NAD(P)H : quinone oxidoreductase inducer activity of extracts of some Saudi Arabian medicinal plants indicates the presence of specific phytochemicals which have the potential to protect against chronic degenerative diseases.