In Vitro Studies of the Effects of Purple Tea (Camellia Sinensis) Extracts on Selected Human Cancer Cell Lines and Multi-drug Resistant Bacteria

Abstract

The objective of this study was to determine the anti-proliferative properties of crude extracts of purple tea on breast cancer (JIMT1), cervical cancer (HeLa), prostate cancer (PC3), liver cancer (HepG2) and ovarian cancer (A2780 cisplatin sensitive and resistant) cell lines; and to determine the anti-bacterial properties on multi-drug resistant strains of Klebsiella pneumonia DSM 26371, Pseudomonas aeruginosa DSM 102274, Escherichia coli DSM 22311, Shigella sonnei DSM 25715, Staphylococcus aureus DSM 102265 and Acinetobacter baumannii DSM 105126. Purple tea (Camellia sinensis) leaf samples were obtained from Tumoi Tea farm in Nandi County. Specific phytochemical tests were performed to screen aqueous and organic extracts of purple Camellia sinensis leaves for the presence of various bioactive compounds. The phytochemical screening revealed the presence of phenols, alkaloids, steroids, flavonoids and tannins in all extracts except those of ethyl acetate. Aqueous and ethanol extracts contained the highest number of bioactive compounds and were therefore selected for further studies. Anti-proliferative assay performed indicated that aqueous extract inhibited 50% of the total cancer cells in the following decreasing order: A2780s, JIMT1, A2780cp, HeLa, PC3 and HepG2. Ethanol extracts also showed inhibitory effects in the decreasing order: A2780s, A2780cp, JIMT1, PC3, HeLa and HepG2. Both aqueous and ethanol extracts exhibited highest anti-proliferative activity against A2780s ovarian cancer cell line with IC50 values of 36.84μg/ml and 56.54μg/ml, respectively. Both aqueous and ethanol extracts also showed higher activities against A2780cp ovarian cancer cell and JIMT1 breast cancer cell with IC50 values of 75.97μg/ml and 93.52μg/ml; and 72.09μg/ml and 116.73μg/ml, respectively. Aqueous and ethanol extracts showed lowest anti-proliferative activity against HepG2 liver cancer cell lines with IC50 values of 1.4*104μg/ml and 463.6μg/ml, respectively. However, ethanol extract enhanced the growth of HeLa, PC3 and HepG2 cancer cells at concentrations of 0-125 μg/ml, 0-100 μg/ml and 0-150 μg/ml, respectively, before showing its inhibitory effect. Aqueous extract completely inhibited A2780s, A2780cp and JIMT1 cancer cell lines at concentrations of 75μg/ml, 200μg/ml and 125μg/ml, respectively. Complete cell inhibition was also exhibited by ethanol extract on A2780s and A2780cp at concentrations of 100μg/ml and 200μg/ml. For antibacterial susceptibility test, micro-broth serial dilution and spot plating methods were used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) after incubation at 37ₒC for 24 h, respectively. All multi-drug resistant strains of bacteria tested were sensitive to aqueous purple tea extract with MIC values

ranging from 0.0064 mg/ml to 6.4 mg/ml and MBC values ranging from 0.0064 mg/ml to 12.8 mg/ml. The highest antimicrobial activity was recorded against methicillin resistant- Staphylococcus aureus (0.0064mg/ml-0.032mg/ml), followed by Shigella sonnei and Pseudomonas aeruginosa (1.6 mg/ml- 3.2 mg/ml). These results show that both aqueous and ethanol extracts of purple Camellia sinensis have various bioactive compounds with varying degrees of anti-proliferative and antimicrobial activities; and may be a promising source of new anticancer and antibacterial agents for treatment of various types of cancer and infections caused by multidrug resistant bacteria, respectively. Therefore, further studies should aim at isolating individual bioactive compounds and determination of the most active compounds so as to maximize their potential use as chemotherapeutics.