Antimicrobial and Antioxidant Activity of the Essential Oils Obtained from Mentha longifolia L. Hudson, Dried by Three Different Techniques

The way of drying the fresh herbal material influences the chemical content and the biological activities of their essential oils. The influence of the different drying methods of the herb Mentha longifolia (L.) Hudson on the antioxidant and antimicrobial activity of the extracted essential oils has been analyzed in this study. Drying has been carried out in three ways: in the natural way, in the laboratory oven (45 degrees C) and in the absorptional low-temperature condensational drier (35 degrees C). The antioxidant activity of the essential oil has been estimated by FRAP and DPPH assays, while the antimicrobial activity has been estimated by the diffusible and micro-delusional method, testing on the nine types of bacteria and two types of fungi. The essential oil obtained from the herb dried in the natural way has shown the highest antioxidant activity and the lowest from the herb dried in the laboratory oven. Bacillus subtilis, Micrococcus luteus and Enterococcus faecalis have shown the highest sensitivity on the three samples. The oil obtained from the herb dried in the absorptional low-temperature drier has shown the strongest antimicrobial effect.