Antioxidant capacity, phenolic, flavonoid, and ascorbic acid contents of Gunnera perpensa from Lesotho, Southern Africa
Poloko Stephen Kheoane and Mokonyana Mohale
Background: Antioxidants play a vital role in oxidizing some harmful reactive oxygen species (ROS) that develop in human bodies due to several body physiological functions and the materials which are ingested into the body. Plant materials provide a good source of natural antioxidants. The known antioxidants from plant sources include phenolics, flavonoids, and vitamin C. Gunnera perpensa had been traditionally used for several decades in the Southern African region to cure several diseases. Its use as an antioxidant could alleviate disease burdens that are caused by the presence of ROS in the human body.
Methods:Gunnera perpensa was extracted in methanol and the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity of extracts was investigated against the ascorbic acid positive control. The estimation of phenolic content was determined using the Folin-Ciocalteu reagent colorimetric method against garlic acid positive control while the flavonoid content was investigated using the aluminium chloride colorimetric method against quercetin as a positive control. The amount of ascorbic acid in the aqueous extract was determined using the iodine titration colorimetric method.
Results:Gunnera perpensa extracts showed a significant free radical scavenging effect (p< 0.05) with an inhibitory concentration (IC50) of 396.82 ± 1.05 µg/mL. The total phenolic content was 146.40 ± 1.94 mg/g gallic acid equivalent (GAE), and its antioxidant activity was mainly due to the presence of phenolics in large amounts as compared to the contents of flavonoids and ascorbic acid. The total flavonoid content was 26.54 ± 2.07 mg/g quercetin equivalent (QE) while ascorbic acid content was 1.56 ± 1.54 mg/100 g of crude plant sample.
Conclusion: Gunnera perpensa could be an alternative natural source of phenols which could be used as antioxidant for eradicating ROS in the human body.