Drying Induced Impact on Composition and Oil Quality of Rosemary Herb, Rosmarinus Officinalis Linn

Abstract

The natural drying of Rosmarinus officinalis Linn. herbs severely affects its volatile oil quality and yields, which is reported here for the first time. The oils obtained through hydrodistillation from fresh, one, two, and three-weeks dried herbs were analyzed by gas chromatography–mass spectroscopy (GC–MS) and gas chromatography–flame ionization detector (GC-FID), and the yields were 198 ± 3.45, 168.7 ± 5.11, and 97.8 ± 1.27 mg, respectively, as compared to the internal referral standard of 327 ± 5.91 mg yield of the one-week dried herbs’ oil. Camphor, the major constituent, significantly depleted from 20.96% to 13.84%, while bornyl acetate yields increased from 1.42% to 12.46% (p values < 0.0001) in three-weeks drying, reflecting the redox processes undergoing within the oil during drying. Several constituents (25) were found in one-week dried herbs’ oil as compared to the fresh, two-, and three-weeks oils, which consisted of 23, 19, and 14 constituents, respectively, leading to the recommendation of the one-week drying of the herb for maximum oil yield. The DPPH (2, 2-diphenyl-1-picryl-hydrazyl) reactivity was highest for the two- and three-weeks dried herb-based oils, followed by the one-week dried- and fresh-herb-based oils (p < 0.0001), again indicating major chemical changes during herbs’ dryings, affecting the free-radical scavenging capacity of these batches of oils obtained after different drying times.