eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2023-03-30 20 1 229 239 10.13005/bbra/3084 43864 article Pooja Malik !* Prashant Upadhyay 1 School of Pharmaceutical Sciences, Faculty of Pharmacy, IFTM University, Moradabad, Uttar Pradesh, India This research aims to prepare microemulsion from Tea Tree and Rosemary essential oil to treat gram-positive and gram-negative bacterial infections. A phase titration has been used to make the proposed microemulsion, which contained 71% water, 23% of a 1:1 mixture of propylene glycol (surfactant), tween 80 (co-surfactant), and 6% of tea tree/rosemary essential oil. In Rosemary essential oil pale yellowish transparent microemulsion, droplet size, zeta potential, and polydispersity index (PDI) of 58.9, 883.6, and 0.678, respectively, showed a stable microemulsion. Tea tree oil loaded in a light, clear microemulsion with zeta potential, droplet size, and polydispersity index (PDI) values of 265.9, 746.8, and 0.987, respectively, indicated a stable microemulsion. The RMO/TTO micro emulsion's viscosity was 1.844/1.933 cps, and its pH ranged from 4.69 to 5.59. The formulation was determined to be a safe, reliable, and effective one in light and good in stability experiments. Escherichia coli, Staphylococcus aureus, and Candida albicans can all be treated using a microemulsion that contains 6% tea tree oil and rosemary oil by agar well diffusion method. Both the EOs-based microemulsion showed more zone of inhibition against Escherichia coli and Candida albicans while Staphylococcus aureus is the less susceptible zone of inhibition. The microemulsion formulation's minimum inhibitory concentration was effective against Staphylococcus aureus, Candida albicans, and E. coli on all physiological parameters.  It can be concluded that TTO/RMO essential oil-loaded microemulsion is considered a promising substitute for the current gram-positive and gram-negative regimens. https://www.biotech-asia.org/vol20no1/formulation-and-evaluation-of-tea-tree-rosemary-essential-oil-based-microemulsion-for-antimicrobial-activity/ Antibacterial; Antifungal Activity; Essential Oil; Microemulsion; Rosemary oil; Tea tree oil