ANTIOXIDANT AND CYTOTOXIC ACTIVITIES OF TECTONA GRANDIS LINN. LEAVES

ABSTRACT

Cancer prevention and treatment have attracted increasing interest. Leaves of Tectona grandis Linn. (Verbenaceae) are widely used in the folklore to treat various types of diseases. This study characterizes the antioxidant activity, total phenolic content (TPC) and cytotoxic activity of different methanolic extracts as well as the derived subfractions (Pet. ether; CHCl₃, EtOAc and n-BuOH) from the 90% methanolic extract of T. grandis. The antioxidant activity was evaluated via three assays; 1,1'-diphenyl-2-picraylhydrazyl free radical (DPPH), phosphomolybdenum method (total antioxidant capacity; TAC and reducing power antioxidant assay (RPAA). Due to the high antioxidant activity of the tested fractions, their cytotoxic activity was evaluated via using preliminary brine shrimp lethality test and toward liver cancer cell line; HepG2 using Sulphorhodamine-B assay. The DPPH activity was ranged from (15.78, 10.63 and 19.58 µg/ml); TAC was ranged from (477.58, 589.50 and 400.30; mg AAE /g extract); RPAA (OD value) was ranged from (0.699, 0.783 and 0.423; 200 mg/ml) and TPC was ranged from (208.32, 400.56 and 295.67; mg GAE/g extract) all respectively for defatted 90% methanol, n-BuOH and EtOAc fractions. A positive linear relationship existed between antioxidant activity and TPC (all R² values > 0.91). The mortality of brine shrimp larvae (LC₅₀) against different dosage of defatted 90% methanol, n-BuOH and EtOAc respectively was (100, 15.84 and 125.89). The HepG2 results showed that defatted 90% MeOH and n-BuOH fractions have cytotoxic activity with IC₅₀ ≤ 20μg/ml which falls within the American Cancer Institute criteria. It was concluded that T. grandis extracts possess a powerful antioxidant and cytotoxic activities.

Key words: Tectona grandis, Antioxidant activity, Cytotoxic activity, Total phenolic content.