Abstract:
Infusions such as teas (made from Camellia sinensis L.) and tisanes (made from
herbs, spices, or other plant parts) have been used for centuries in traditional
therapy. In the study, green tea (Camellia sinensis) and stinging nettle (Urtica
dioica) are mixed in different proportions (1.5:1.5, 1.8:1.2, 2.1:0.9, 2.4:0.6,
2.7:0.3) to obtain an optimum formulation of a blended tea using DOE and
based on sensory characteristics that were further investigated as potential
antibacterial agents. Green tea, U. dioica leaves and the selected tea blend was
subjected to organic solvent extraction (methanol and ethanol) as well as
aqueous extraction. Major phytochemicals (phenols, flavonoid, and tannin)
along with the antioxidant activity (DPPH radical scavenging activity, TAC,
and FRAP) were determined for the prepared extracts. The antibacterial
properties were evaluated by the agar well diffusion method. Minimum
inhibitory concentration was evaluated by the micro well dilution method.
The sensory analysis was carried out for brew appearance, aroma, color and
overall acceptance of five tea infusions, and from the result, sample C (green
tea: U. dioica leaves; 2.1:0.9) was found superior to other samples. Among the
plant extracts tested, the blend extracts in methanol gave the highest TPC
(387.11mgGAE/g), TFC (167.57mgQE/g), Tannin (47.68mgGAE/g), DPPH
radical scavenging activity (98.32%), TAC (15.38mgAAE/g), and FRAP
(15.12AAE/g) (p<0.05). The best antimicrobial actions were observed in the
blend extract against the five clinical isolates. The most effective activity was
proven against S. aureus with a maximum ZOI of 18mm, 18mm, and 10mm in
methanol, ethanol, and aqueous solvent respectively, and a minimum inhibitory
concentration value of 50µg/ml against E. faecalis at 3.2mg/ml. The study
concluded that green tea and stinging nettle are in fact more effective as
mixtures (2.1:0.9), implying that the combined preparation can synergistically
enhance antioxidant as well as antibacterial properties
Description:
A
Dissertation
Submitted to the Department of Microbiology,
Central Campus of Technology, Tribhuvan University, Dharan,
Nepal, in the partial fulfillment of the Requirements for the Award
of Degree of Masters of Science
(Food Microbiology)
