Tea leaves potentiate antimicrobial effect against pathogens depending on harvesting season and altitude-mediated change in their biochemical concentrations

Tea is the most popular non-alcoholic beverage with immense medicinal and therapeutic value. The tea leaves harvested at various seasons from two tea gardens were assessed for their biochemical concentrations and potential antibacterial activities against various bacteria. The total polyphenol content, total flavonoid content and tannin content for lower altitude tea leaves ranged from 315.02 to 452.78 mg ­g⁻¹, 124.77 to 197.46 mg g­ ⁻¹ and 14.97 to 21.97 mg g­ ⁻¹, respectively, whereas, it ranged from 298.10 to 403.72 mg ­g⁻¹, 111.78 to 184.89 mg ­g⁻¹ and 13.82 to 19.69 mg ­g⁻¹, respectively, for higher altitude tea leaves. Except for tannin content in lower altitude tea leaves, all biochemicals exhibited higher concentrations in spring tea as compared to other seasons. The tea leaves extract also showed a broad-spectrum antibacterial activity against the tested bacteria. The spring and winter tea exhibited the highest and the least antibacterial activity against most of the bacteria, respectively. Between tea gardens, the lower altitude tea leaves extract had higher biochemical concentrations and exhibited greater antimicrobial activity against bacterial pathogens in most seasons. A strong direct correlation was established between the inhibition zone and tea leaves biochemicals whereas, minimum inhibitory concentration and minimum bactericidal concentration had an inverse correlation with tea leaves biochemicals. The study further elucidates the dependence of tea extracts antimicrobial potency on bacterial species where gram-positive bacteria were more sensitive as compared to gram-negative. This research sheds light on tea leaves as a promising source of natural antimicrobials and discloses the importance of its harvesting season as well as the location for their biochemicals and antimicrobial activities.