In vitro antioxidant and cytotoxic activity of Gunnera perpensa L. (Gunneraceae) from South Africa

Gunnera perpensa L. (Gunneraceae) is a medicinal plant used by Zulu traditional healers to induce labor, expel the placenta after birth and to relief menstrual pains. Phytochemical screening of the rhizomes revealed the presence of alkaloids, flavonoids, steroids, saponins, tannins and glycosides. Methanol extracts of G. perpensa exhibited strong scavenging of 2,2-Diphenyl-1-picryl-hydrazyl (DPPH) and 3-ethylbenzothiazoline-6-sulfonate (ABTS), but showed poor (< 50%) radical scavenging of nitric oxide, superoxide and hydroxyl radicals. At a concentration of 5 mg/100 ml, the extract was able to inhibit lipid peroxidation of the whole rat brain homogenate (71.13%) and lipoxygenase (30%) activity. The plant extract also contained reduced form of nicotinamide adenine dinucleotide (NADH, 3.8 ρm/g), total phenol (248.45 mg/g) and traces of sulfhydryl groups (SH). The total antioxidative capacity was 36% relative to ascorbic acid (AA) and 64% relative to butylated hydroxyl toluene (BHT). The cytotoxicity of the extract (LC ₅₀) to brine shrimp larvae was 137.62 mg/ml. It is apparent that the antioxidant activity of G. perpensa contributes to its effectiveness in folk medicine.