Antioxidant Activity of Thebu (Costus speciosus) Rhizome and Leaves

Abstract

Thebu (Costus specious) is an important medicinal plant that is freely available in Sri Lanka. The rhizomes of Thebu plant is a rich source of antioxidant. But due to the damage cause to the plant, use of rhizomes in commercial production of antioxidants is limited. Thus, in the current study, use of tender and mature leaves to extract natural antioxidants was investigated. The antioxidant potential of hexane extracts of tender leaves, mature leaves and rhizomes were evaluated using DPPH radical scavenging and ferric reducing power assays. The total phenolic content and flavonoid contents of each extract were also measured. The total phenolic content of tender leaves, mature leaves and rhizomes from Galle & Colombo districts were more or less similar (0.02 - 0.03 mg gallic acid eq/g extract). On the other hand, the hexane extract of mature leaves from both districts showed significantly higher amount of flavonoid content (6.36 ± 2.66, 6.86 ±1.47 mg quercetin eq/g extraction Galle and Colombo respectively) than tender leaves. Compared to tender leaves and rhizomes, particularly higher amount of DPPH radical scavenging activity was exhibited by mature leaves from both Galle and Colombo districts with 1.37±0.38, 1.71±0.6 mg trolox eq/g extract respectively). The results indicate that mature leaves of C. specious are rich in total flavonoid and DPPH radical scavenging activity than the rhizomes. Thus mature leaves ofThebu plant can be used in commercial production of natural antioxidants.