Analysis of oxidative stress and wound-inducible dinor isoprostanes F-1 (phytoprostanes F-1) in plants

Isoprostanes F-2 are arachidonate autoxidation products in mammals that hav e been shown to be induced during several human disorders associated with e nhanced free-radical generation. Isoprostanes F-2 represent not only extrem ely reliable markers of oxidative stress in vivo, but they also exert poten t biological effects. Therefore, it has been postulated that isoprostanoids are mediators of oxidant injury in vivo. Higher plants, however, do not sy nthesize arachidonic acid or isoprostanes. Here we show that a series of is oprostane F-2 analogs termed phytoprostanes F-1 (previously diner isoprosta nes F-1) are formed by an analogous pathway from alpha -linolenate in plant s. High-performance liquid chromatography and gas chromatography-mass spect rometry methods using [O-18](3)phytoprosranes F-1 as internal standard have been developed to quantify phytoprostanes F-1. In fresh peppermint (Mentha piperita) leaves, phytoprostanes F-1 were found in free form (76 ng/g of d ry weight) and at about 150-fold higher levels esterified in lipids. It is notable that these levels of phytoprostanes F-1 are more than two orders of magnitude higher than the basal levels of isoprostanes F-2 in mammalian ti ssues. Furthermore, wounding, as well as butyl hydroperoxide or cupric acet ate stress triggered a dramatic increase of free and esterified phytoyrosta nes F-1. Thus Fhytoprostanes F-1 may represent a sensitive measure of oxida tive damage in plants similar to isoprostanes in mammals. However, one of t he most exciting issues to be clarified is the possibility that linolenate- derived phytoprostanes F-1 exert biological activities in plants and/or ani mals.