Drying Induced Impact on Composition and Oil Quality of Rosemary Herb, <i>Rosmarinus Officinalis</i> Linn.

• Main Authors: Hamdoon A. Mohammed, Mohsen S. Al-Omar, Salman A. A. Mohammed, Mohamed S. A. Aly, Abdulmalik N. A. Alsuqub, Riaz A. Khan
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: Molecules
• Subjects: Rosmarinus officinalis; volatile oils; natural drying; antioxidant activity; compositional ratio
• Online Access: https://www.mdpi.com/1420-3049/25/12/2830

The natural drying of <i>Rosmarinus officinalis</i> 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% (<i>p</i> 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 (<i>p</i> < 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.