effects of cassia obtusifolia sicklepod extracts and anthraquinones on muscle mitochondrial function naturally occurring quinones and quinonecontaining extracts of seeds of the toxic plant cassia obtusifolia sicklepod affected muscle mitochondrial function aqueous suspensions and organic extracts of c obtusifolia seeds slightly elevated plasma creatine kinase levels of spraguedawley rats these extracts were analyzed by fused silica capillary gas chromatography and found to contain nine anthraquinones and three anthrones urinary metabolites primarily consisted of betaglucuronide conjugates of the anthraquinones the three anthrones or conjugate analogues were not present in the urine in detectable amounts emodin doxorubicin and organic extracts of c obtusifolia inhibited nadhcytochrome c oxidoreductase activity of bovine heart mitochondrial particles and nadhcoq oxidoreductase activity of porcine heart mitochondrial nadh dehydrogenase whereas juglone was stimulatory relative quinone metabolism correlated with semiquinone formation rate and with redox potential a protective effect of coenzyme q against enzyme inhibition by anthraquinones was also observed