Vetiver is a plant whose root essential oil is used in perfumery. Does the combination of constituents change depending on whether harvested roots are distilled fresh or after drying? And does that change occur in the same way regardless of where the material was grown?
Niloofar Aryanasl and colleagues compared fresh and dried roots from vetiver accessions associated with four regions of Iran. The peer-reviewed paper was published on September 8, 2026, and is currently an early-access version awaiting replacement by the final edited version. Its aim was to examine location-associated compositional differences and post-harvest drying effects within the same analysis.
Twenty-four extractions from the roots of 12 plants
The material consisted of three-year-old vetiver grown on farms in Tehran, Gorgan, Saveh, and Boushehr. Three plants from each location-associated accession were sampled separately, giving 12 plants in total. Roots from different plants were not pooled.
The roots of each plant were divided into two portions: one was used fresh, and the other was shade-dried at room temperature for 10 days. Each portion underwent 24-hour hydrodistillation, giving four accessions × three plants × two treatments, or 24 extractions and chemical analyses. This was a matched comparison of two treatments from the same plants, not a comparison of 24 independently grown plants.
Both fresh and dried root samples weighed 50 g when used for distillation. Because drying removes water, however, the same 50 g does not represent the same original amount of fresh roots. This difference in mass basis also needs attention when comparing recovered oil quantities.
The measurements describe relative proportions
The essential oils were separated by gas chromatography, and 50 compounds were tentatively assigned by comparing information including mass spectra with known data. These were putative molecular annotations, not final identifications confirmed through direct comparison with authentic standards.
Composition was expressed as each compound’s chromatographic peak area relative to the total. A higher proportion does not necessarily mean a greater absolute amount, because the proportion can also rise when other constituents decrease. Nor did the study involve people smelling the oils to evaluate intensity or preference.
The four accessions did not respond uniformly to drying
Oxygenated sesquiterpenoids predominated in all accessions. Sesquiterpenoids are a family of compounds associated with a basic 15-carbon framework. The study compared this oxygen-containing group separately from sesquiterpene hydrocarbons, which consist of carbon and hydrogen.
The proportion of oxygenated compounds increased significantly after drying in Tehran and Gorgan, but did not change significantly in Saveh or Boushehr. The hydrocarbon group decreased after drying in Tehran and Gorgan and increased in Saveh and Boushehr. Drying therefore did not cause a uniform directional change.
Individual compounds also behaved differently. Looking at means alone, the proportion of khusimol, a characteristic vetiver constituent, increased after drying in all four accessions, but significant increases were confirmed only in Gorgan and Saveh.
The proportion of β-vetivone increased after drying in Tehran and Saveh, decreased in Boushehr, and did not change significantly in Gorgan. α-Vetivone increased in Tehran, Gorgan, and Saveh, with no significant change in Boushehr. Even within vetiver, which constituents became more prominent after drying depended on the material.
Location differences cannot simply be attributed to climate
The researchers also summarized patterns in the 15 major compounds to examine similarities among samples. There were groupings associated with location and treatment, but oxygenated sesquiterpenoids predominated in every sample. The samples did not separate into two distinct types, one oxygenated-rich and the other hydrocarbon-dominant.
Each accession was grown in one location. This design cannot separate genetic differences from differences in climate, soil, or cultivation management. Although the material was propagated vegetatively, genetic identity had not been confirmed at the molecular level.
The results therefore cannot establish explanations such as higher humidity causing a compound to increase or a hot, dry location producing a particular composition. Evaporation and oxidation during drying may also have contributed to the changes, but those reactions and enzyme activities were not measured directly.
Summary
The compositional changes associated with drying vetiver roots were not uniform across the four accessions. At both the broad chemical-class level and the level of individual constituents, proportions could increase, decrease, or show no clear change after drying.
This study does not determine which origin produces the highest quality or whether drying invariably improves odor. It provides baseline evidence that evaluating post-harvest handling requires following both differences in starting material and compound-specific responses. The authors point toward studying more accessions, controlled drying conditions, absolute compound quantities, and genetic and cultivation-environment information to identify reproducible compositional features.
The study was supported by the Research Council of Shahid Beheshti University. The authors declared no conflicts of interest.
References
Aryanasl, N., Sonboli, A., Rezghiyan, A., Eghlima, G., & Mirjalili, M. H. (2026). Chemical composition and essential oil diversity of chrysopogon zizanioides roots from four regions of Iran comparing fresh and dried samples. Scientific Reports, peer-reviewed early-access version (Article in Press). DOI: 10.1038/s41598-026-70223-z / Full text. © 2026 The Author(s). CC BY-NC-ND 4.0.
