mechanisms of non-enzymatic antioxidant defense system of different organs of catharanthus roseus for protective of cell membrane

background & aim: when the level of free radicals is increased and also when both the enzymatic systems and low molecular antioxidants are not sufficient to protect the organism, it seems necessary to get antioxidants from external sources. this study aimed to evaluate the antioxidant potential of different parts of catharantus roseus experimental: the antioxidant potential of ethanol extracts of roots, stems, leaves, flowers, seed pods and seeds of c. roseus  plant were measured based on 1,1-diphenyl-2-picrylhydrazyl (dpph) free radical scavenging, inhibition of linoleic acid peroxidation by ferric thiocyanate (ftc), and malondialdehyde inhibition by thiobarbituric acid method (tba) against the standards: butylated hydroxytoluene (bht), butylated hydroxyanisole (bha) and ascorbic acid.   results & discussion: the phenolic content in the root (61.61 ± 2.58 µg of gallic acid per mg of dried weight extract) according to folin–ciocalteu method were more than any other organs. in scavenging a half of dpph• free radicals (ic50), the extract of root, seed, and leaf (238.9 ± 2.02, 253.78 ± 1.42, 277.95 ± 2.56 µg ml-1),respectively, had the best performance.  in the inhibition of linoleic acid peroxidation, the root extract had the best inhibitory power after ascorbic acid and bht, and the leaf and seed extract had the performance similar to bha. the root (78.68 ± 0.54%), and seed (77.44 ± 0.66%) had the best performance in the inhibition of mda compared with other extracts. pearson correlation coefficients between the phenolic content and antioxidant capacity of extracts were high and equal to -0.838, 0.895, and 0.740, respectively, according to dpph, ftc and tba methods. industrial and practical recommendations: the results of this study can be promising in the potential of other applications of the plant organ especially in the inhibition of free radicals and lipids' peroxidation.