Plants for diabetes: Identification of plant extracts and metabolites as partial PPARγ agonists with potential anti-diabetic effects

Lifestyle-associated diseases like type 2 diabetes mellitus (T2D) have become one of the largest health problems worldwide. Treatment of T2D often includes the use of expensive drugs with severe side effects, like the thiazolidinediones (TZDs). This is by far an optimal situation, and alternative treatments that are more effective and more accessible are needed, as T2D and obesity is spreading like an epidemic throughout the world. More than 1200 plants have been used traditionally for the treatment of diabetes, although evidence for their effects is limited. Compounds derived from plants might prove to be a good alternative in the treatment of T2D if their effect can be documented. „Plants for diabetes“ is a 3-year EU Interreg IIIA project, which was initialized in 2005 with the ambition to identify plant candidates with potential anti-diabetic effects. Twenty-four plant species were selected for investigation of potential anti-diabetic effects in the project and a screening platform that enables identification of partial peroxisome proliferator-activated receptor (PPAR) γ agonists were used to assess the anti-diabetic potential of these. Sixty percent of the plant extracts screened were shown to contain compounds with effects similar to those of partial PPARγ agonists. Extracts of purple coneflower (Echinacea purpurea), savoury (Satureja sp.), and elderflowers (Sambucus nigra) were some of the best candidates and were selected for bioassay-guided fractionation. Bioassay-guided fractionation of these yielded several compounds with promising effects on PPARγ. The potential active compounds comprised different classes of natural products, including fatty acids and fatty acid derivatives, terpenes and flavonoids. The majority of these constituents have previously shown an effect in pure form but not as part of plant extracts. Hence, this project has revealed a large potential for future use of plant extracts and plants in the treatment of T2D.