There is abundant evidence that
reactive oxygen species are implicated in several physiological and
pathological processes. To protect
biological targets from oxidative damage,
antioxidants must react with radicals and other reactive species faster than
biological substrates do. The aim of the present study was to determine the in vitro
antioxidant activity of aqueous extracts from leaves of Bauhinia forficata Link (Fabaceae-Caesalpinioideae) and Cissus sicyoides L. (Vitaceae) (two medicinal plants used popularly in the control of
diabetes mellitus), using several different assay systems, namely,
2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (
ABTS) decolorization,
superoxide anion radical (O2(.-)) scavenging and
myeloperoxidase (MPO) activity. In the
ABTS assay for total
antioxidant activity, B. forficata showed IC50 = 8.00+/-0.07 microg/mL, while C. sicyoides showed IC50 = 13.0+/-0.2 microg/mL. However, the extract of C. sicyoides had a stronger effect on O2(.-) (IC50 = 60.0+/-2.3 microg/mL) than the extract of B. forficata (IC50 = 90.0+/-4.4 microg/mL). B. forficata also had a stronger inhibitory effect on MPO activity, as measured by
guaiacol oxidation, than C. sicyoides. These results indicate that aqueous extracts of leaves of B. forficata and C. sicyoides are a potential source of natural
antioxidants and may be helpful in the prevention of
diabetic complications associated with oxidative stress.