Determination of major chemical constituents and antimicrobial activities of essential oils extracted from Nonsaleable Grade (NSG) spices of Cymbopogon nardus, Rosmarinus officinalis, Thymus vulgaris and Coriandrum sativum seeds

Four non-saleable grade (NSG) plant spices, including Cymbopogon nardus (citronella), Rosmarinus officinalis (rosemary), Thymus vulgaris (thyme), and Coriandrum sativum (coriander) seeds were extracted using hydro-distillation. The chemical compositions of essential oils were analyzed using gas chromatography coupled with mass spectrometry (GC-MS) and the antimicrobial activities were tested to against the microbes of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans). Four essential oils are corresponding to the main functional substances of citronellal (29.562%), 1, 8- Cineole (62.267%), thymol (42.579%), and linalool (76.512%). Both the chemical constituents and antimicrobial activity of NSG essential oils were similar to both commercial products and those reported in previous studies, some of NSG essential oils even present better antimicrobial activity than commercial ones. This new approach of using NSG spices can help to reduce agricultural waste and increase the revenue of spice farmers.