Role of Essential Oils of Medicinal Plants (Eucalyptus Globulus, Thuja Occidentalis, Rosmarinus Officinalis, Lavandula Officinalis) to Treat Broad Spectrum Bacterial and Fungal Pathogens and as Antioxidants in Food and Health

Abstract

Essential oils (EOs) have attracted attention due to considerable interest in health, food and pharmaceutical industries. The aim of the present study was to screen EOs from leaves of Eucalyptus globulus, Thuja occidentalis, Rosmarinus officinalis, Lavandula officinalis for antimicrobial (antifungal and antibacterial) and antioxidant properties and develop EO as broad spectrum antimicrobials and functional food ingredient. The fresh leaves of Eucalyptus globulus, Thuja occidentalis, Rosmarinus officinalis, Lavandula officinalis were subjected to hydro distillation.. The percent yield (v/w) of essential oil varied from 0.3 – 1.6%, with highest yield from Eucalyptus globulus and lowest from Thuja occidentalis. The EOs were used to study antioxidant activity by DPPH (2, 2-diphenyl-1- picrylhydrzyl) and ABTS (2, 2-azino-bis3-ethylbenzothiazoline-6-sulphonic acid) assays. All the EOs exhibited strong antioxidant activity with IC50 values of 0.13 – 0.35 using DPPH assay and 0.6-0.98 using ABTS assay for different EOs. EO of Eucalyptus globulus showed highest antioxidant potential as measured using DPPH and ABTS assays. Further, EOs were tested for antimicrobial activity against bacterial strains (B. subtilis, S.aureus, E. coli and K. pneumonia) and fungal strains (Candida albicans ATCC90028 and MTCC277 and Saccharomyces cerevisiae H1086). EO from Eucalyptus globulus and Thuja occidentalis showed strong antibacterial activity against Gram positive bacteria, whereas Rosmarinus officinalis and Lavandula officinalis were highly effective against Gram negative bacteria. Further, EO from Eucalyptus globulus showed strongest anifungal activity against three fungal strains. On the other hand, EO from Rosmarinus officinalis and Lavandula officinalis showed antifungal activity only against Candida albicans (MTCC277). The MICs value for all the four essential oils ranged between 0.31- 1.25 % against bacterial strains and 0.15- 0.62% against fungal strains. This data clearly suggest that these EOs under study are broad spectrum antimicrobials, but more effective therapeutics against unicellular fungi. Based on our current study, the EOs of these plants could be developed as functional food ingredient cum food preservatives and broad spectrum antimicrobials against bacterial and fungal pathogens.