Antioxidant potential of leaf extracts from Zingiber officinale Roscoe and Curcuma longa L.

Abstract

The rhizomes of the turmeric (Curcuma longa L.) and ginger (Zingiber officinale Roscoe) plant are commercialized for culinary and medicinal use, presenting antioxidant, anti-inflammatory and even antitumor activity. The leaves of these plants are considered post-harvest waste. The aim of this study was to evaluate the antioxidant potential of turmeric and ginger leaf extracts. After drying the leaves in an oven at 40ºC, cold extraction was performed by exhaustive maceration in methanol. The methanolic crude extract was partitioned in ascending order of polarity and the hexane, dichloromethane, ethyl acetate and hydromethanolic fractions were obtained. The antioxidant activity of the extracts and fractions was evaluated by the DPPH and ABTS methods and the results were expressed in μM of Trolox per g/extract. By the DPPH method, both in turmeric and ginger, the fraction that showed the highest antioxidant activity was ethyl acetate (752.18 and 393.32 μM Trolox/g, respectively). For ABTS, the highest antioxidant activity was in dichloromethane (935.54 and 704.31 μM Trolox/g, respectively), followed by ethyl acetate (393, 23 and 607.77 μM Trolox/g, respectively), indicating turmeric with higher antioxidant potential.