Antioxidant, cytotoxic, antibacterial and thrombolytic activities of Centella asiatica L.: possible role of phenolics and flavonoids

Background Centella asiatica L. (Apiaceae), a green leafy vegetable, has been used as a popular folk medicine in Bangladesh in the treatment of various ailments. The plant is reported to contain phenolics and flavonoids, but their bioactive potentials are not yet completely known. The present study was designed to investigate the role of the phenolic and flavonoids in the antioxidant, cytotoxicity, antibacterial and thrombolytic activities. Methods Four solvent fractions viz. methanol (MSF), ethyl acetate (ESF), chloroform (CSF) and petroleum ether (PSF) were prepared from the dried powder of the whole plant by the modified Kupchan method. Total phenolic content and flavonoid content were determined by Folin Ciocalteu method and aluminum chloride colorimetric method, respectively. The antioxidant activity was assessed by the DPPH radical scavenging and total antioxidant capacity assays. The antibacterial activity was determined by the disc diffusion method and cytotoxicity was evaluated by the brine shrimp lethality bioassay. Thrombolytic activity was assayed using streptokinase as standard. Results Qualitative analysis of phytochemical revealed the presence of phenolics and flavonoids along with other bioactive constituents. Among the extractives, CSF contained the highest content of phenolics (155.46 ± 0.52 mg GAE/g) and flavonoids (345.17 ± 1.12 mg QE/g) and exhibited the most potent antioxidant activity in terms of total antioxidant capacity (179.01 ± 0.89 mg AAE/g) and DPPH scavenging ability (IC 50 ; 15.31 ± 0.32 µg/mL). Similarly, CSF showed the highest cytotoxicity with LC 50 values of 13.80 ± 0.23 µg/mL, and thrombolytic activity with 43.94 ± 0.62% clot lysis. The fraction also exhibited broad spectrum antibacterial activity. A significant correlation was observed between the flavonoid content and total antioxidant activity (r 2 = 0.894, p < 0.05), while high correlation was seen between phenolic and flavonoid content and DPPH radical scavenging, total antioxidant capacity and cytotoxicity (r 2 = 0.612–0.928). Similarly, a positive correlation was found between phenolic and flavonoid content with thrombolytic and antibacterial activities. Conclusion These results revealed that C. asiatica is a rich source of phenolics and flavonoids and correlated with antioxidant, cytotoxicity, antibacterial and thrombolytic activities. Hence isolation of phenolics and flavonoids from this plant may offer potential candidates which may be effective in the prevention of many chronic diseases.