Antimicrobial Properties of Polyphenolic Extracts from Selected Kenya’s Specialty Tea Camellia Sinensis on Pathogenic Bacteria and Fungi

Abstract

Tea Camellia sinensis has received attention due to its high levels of polyphenols that are associated with human health properties such as anti-inflammatory, antioxidant, antibacterial and antifungal effects. However, microbial resistance has reduced the effectiveness of several conventional antimicrobial agents currently used to manage bacterial and fungal infections. Therefore, the development of new, natural antimicrobial products from plant sources with higher potency and fewer side effects is critical in overcoming the emerging challenge of antibiotics resistance. This study evaluated the antimicrobial activity of specialty tea extracts that include oolong, purple, yellow, green and black orthodox teas. They were extracted using hot distilled water, methylene chloride and ethyl acetate. Selected pathogenic bacteria strains included Penicillinase-Methicillin antimicrobial resistance Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853. Fungal strains included Candida albicans ATCC 90028 and clinical isolate Trichophyton mentagrophytes. Total polyphenols content was analyzed using Folin-Ciocalteu method. Individual catechins and caffeine content were profiled using High Performance Liquid Chromatography (HPLC-PDA) machine and antioxidant activity was determined by DPPH assay. All experimental data were analyzed using analysis of variance (ANOVA) to determine statistically significant differences among treatment means at 95% confidence level (p< 0.05). For post hoc analysis, Duncan’s Multiple Range Test (DMRT) was applied to separate group means and identify significant differences. Water extracts had the highest total yield (82.2%) while methylene chloride had the least (2.63%). Ethyl acetate extracts contained highest polyphenol content (11.4% -78.1%) and catechin content (46.6% - 75.9%), contrary to, methylene chloride extracts which had low total catechin contents (1.2% to 4.5%). Caffeine was predominantly in methylene chloride extracts (29.97% - 58.99%). Antimicrobial activity was tested using disc diffusion method. Ethyl acetate extracts showed the strongest antimicrobial activity, with an inhibition zone of 23mm against methicillinpenicillinase resistant staphylococcus aureus ATCC 25923 at 10 mg/ml concentration. Water and residual extracts also had a moderate inhibition zone of 18mm and 14mm, respectively, while methylene chloride exhibited weak activity (8mm) at 10mg/ml concentration. Ethyl acetate extracts also showed antimicrobial activity against Candida albicans ATCC 90028 and clinical isolate Trichophyton mentagrophytes with an inhibition zone of 12mm and 16mm respectively, at 1mg/ml concentration. The lowest dilution concentration of 0.31mg/ml exhibited zone of inhibition of 9mm for methicillin -penicillinase resistant Staphylococcus aureus ATCC 25923. However, no antimicrobial activity was observed against Pseudomonas aeruginosa ATTC 27853. The data confirm that the choice of solvent significantly impacts both composition and bioactivity. Ethyl acetate was most effective solvent for extracting bioactive compounds. Kenya specialty teas demonstrated broad-spectrum of antimicrobial potential, supporting their use as natural alternatives antimicrobial agents