Screening of herbal extracts for activation of the human peroxisome proliferator-activated receptor

The peroxisome proliferator-activated receptors play a pivotal role in metazoan lipid and glucose homeostasis. Synthetic activators of PPARalpha (fibrates) and PPARgamma (glitazones) are therefore widely used for treatment of dislipidemia and diabetes, respectively. There is growing evidence for herbal compounds to influence nuclear receptor signalling e.g. the PPARs. We recently reported carnosic acid and carnosol, both being diterpenes found in the labiate herbs sage and rosemary, to be activators of PPARgamma. The subsequent screening of a variety of ethanolic extracts, obtained from traditionally used herbs, for PPAR activation, led to an exceptionally high hit rate. Among 52 extracts nearly the half significantly activated PPARgamma and 14 activated PPARalpha in addition, whereas three of them were pan-PPAR activators, which also activated PPARdelta. The most active extracts, for which a concentration dependent effect could be shown, were the extracts of Alisma plantago aquatica (ze xie/european waterplantain), Catharanthus roseus (madagascar periwinkle), Acorus calamus (sweet calamus), Euphorbia balsamifera (balsam spurge), Jatropha curcas (barbados nut), Origanum majorana (marjoram), Zea mays (corn silk), Capsicum frutescens (chilli) and Urtica dioica (stinging nettle). The results of the present study provide a possible rationale for the traditional use of many herbs as antidiabetics.