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In vitro Studies on Antibacterial, Thrombolytic and Antioxidant Activities of Green Tea or Camellia sinensis

This study examined the antibacterial, thrombolytic and antioxidant activity of crude water, ethanol and acetone extracts of Camellia sinensis (Fam: Theaceae) or green tea leaves in vitro. The pharmacological history of this plant inspired us to evaluate the possible antibacterial, thrombolytic and antioxidant potentials. A quick and rapid methodology (In vitro thrombolytic model) was applied to find out the clot lysis effect of aqueous, ethanol and acetone extracts of Camellia sinensis leaves where streptokinase and water were employed as a positive and negative controls, respectively. The percentage (%) clot lysis was statistically significant (p<0.0001) when compared with vehicle control. Using an in vitro thrombolytic model, water, ethanol and acetone extracts of Camellia sinensis leaves showed moderate clot lysis activity (45.60 ± 2.313%, 37.68 ± 2.211%, and 30.51% ± 2.551%, respectively) whereas standard streptokinase showed 87.15 ± 3.212 % clot lysis effect and the negative control water revealed 5.60 ± 2.131 % lysis of clot. In the case of antibacterial activities, the extracts of water, ethanol and acetone solvents were investigated by a simple agar diffusion method using ten pathogenic bacteria. Both aqueous and ethanol extracts showed moderate activity against seven pathogenic organisms, and acetone extracts showed activity against eight of the bacteria tested. All the activities were determined by measuring the zone of inhibition (in mm) compared with the standard antibiotic (Amoxicillin). Finally, Free radical scavenging activity was evaluated in vitro with the spectrophotometric method based on the reduction of the stable 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) free radical. The tested extracts showed variable antioxidant activities. The high antioxidant activity was achieved in water (88.32%) followed by ethanol (78.80%) and acetone (61.96%) extracts. The extracts were investigated regarding their total flavonoid content (TFC) by A1C13 reagent. The aqueous extracts of green tea leaves (TFC = 78.16 ± 1.90 μg/mg) and ethanol extracts (TFC = 65.99 ± 4.11 μg/mg) had the highest content of flavonoid in comparison to acetone extracts (TFC = 55.85 ± 1.43 μg/mg). Furthermore, the total phenolic content of the three extracts of green tea leaves showed large variations. The water extracts of green tea leaves contained the highest total phenol content (160.00 ± 0.62 mg GAE/g extract), followed by ethanol extracts (123.33 ± 2.32 mg GAE/g extract) and acetone extracts (95.37 ± 1.12 mg GAE/g extract).This study suggests that leaves of green tea are the possible sources of natural radical scavengers. Thus, green tea leaves could be used as natural antioxidants in the beverage, food and pharmaceutical industries that need further wide range in vivo studies.

Author(s): Mir Monir Hossain and Shahrin Mahmood

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