Chemists Turn to Eudesmol Isomers to Grade the World’s Priciest Wood

Agarwood, the dark, resin-saturated heartwood formed when Aquilaria trees respond to injury and microbial attack, is one of the most expensive raw botanical materials on Earth, prized for centuries in perfumery, incense and traditional medicine. Yet the way its quality is judged has remained stubbornly old-fashioned: trained assessors sniff, inspect and grade samples by eye and nose, a practice that produces inconsistent results from batch to batch and market to market. A team of South Korean researchers now reports a laboratory-based alternative that could bring the agarwood trade into the era of objective, reproducible quality control, using three closely related aroma molecules as chemical yardsticks.

The study, published in Food Science and Biotechnology by researchers at Dongguk University-Seoul together with colleagues from the research and business development center of Kwangdong Pharmaceutical, focuses on a family of sesquiterpene alcohols known as eudesmols. Three isomers, α-, β- and γ-eudesmol, share the same molecular formula but differ in the arrangement of their atoms, and all three contribute to the complex woody, balsamic character of agarwood resin. Because they are abundant, characteristic and chemically stable components of the resin’s volatile fraction, the team proposed them as quantitative markers of quality, replacing subjective sensory judgment with hard numbers from an instrument.

The analytical strategy unfolded in two stages. First, the researchers characterized what was actually in the samples. They took nine agarwood resin samples originating from Indonesia and analyzed their volatile compounds using headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry, a technique abbreviated HS-SPME-GC/MS. In this method, a thin coated fiber is suspended above the sample to absorb aroma compounds from the headspace, then inserted into a gas chromatograph where the molecules are separated and identified by their mass spectra. The profiling revealed that major sesquiterpenes, including compounds related to selinene and eudesmol, dominated the volatile profile, and these were tentatively characterized by matching their mass spectra against spectral libraries.

Identification alone, however, is not enough for quality control. Mass spectral library matching can tell you what a compound probably is, but it cannot reliably tell you how much of it is present, because mass spectrometry signals vary with ionization efficiency and instrument conditions. For that, the researchers turned to gas chromatography with flame ionization detection, or GC-FID, a workhorse quantitative technique in which separated compounds are burned in a hydrogen flame and the resulting ions produce a current proportional to the amount of carbon arriving at the detector. Flame ionization detection is prized for its stability, wide linear range and excellent precision, making it the method of choice when numbers must stand up to regulatory scrutiny.

The team established and validated a GC-FID method for quantifying the three eudesmol isomers, following internationally recognized analytical validation principles. The performance figures were striking. The method showed excellent linearity, with a coefficient of determination, R², of 1.000 across the calibrated range, meaning the detector response rose in a perfectly straight-line relationship with concentration. Repeatability, expressed as the relative standard deviation of repeated measurements within a single day, was better than 2.7 percent, indicating that the method delivers essentially the same answer every time it is run under the same conditions.

Accuracy was assessed through spike-and-recovery experiments, in which known amounts of each eudesmol isomer were added to samples at three different concentrations and the measured recovery was compared with the expected value. Recovery rates fell within a narrow and reassuring band: 101.9 to 102.8 percent for γ-eudesmol, 101.4 to 101.7 percent for α-eudesmol, and 98.9 to 101.3 percent for β-eudesmol. Values close to 100 percent mean the method neither systematically overestimates nor underestimates the true content, and the tight ranges across concentration levels suggest the assay behaves consistently whether eudesmols are present in small or large amounts.

When the validated method was applied to the nine Indonesian samples, the results revealed just how variable commercial agarwood can be. Total eudesmol content ranged from below the method’s limit of detection all the way up to 16.9 milligrams per gram of resin. That spread, spanning more than an order of magnitude, illustrates precisely why sensory grading has struggled to impose order on the market: samples that might look and even smell superficially similar can differ enormously in their content of the marker compounds. A single numerical measurement of eudesmol content offers buyers and regulators a way to distinguish between them that no nose can match for reproducibility.

Quality, however, is not only about potency; it is also about safety. Because agarwood is burned as incense, infused in preparations and used in food-adjacent applications, contamination with toxic elements or agricultural chemicals is a genuine concern. The researchers therefore screened their samples for heavy metals and for 514 pesticide residues, and reported that the levels found were within acceptable limits. This two-pronged approach, pairing marker quantification with a broad safety screen, mirrors the expectations of pharmacopoeial and food-safety authorities, who increasingly demand both identity and purity data for botanical raw materials.

The significance of the work extends beyond agarwood itself. Botanical and herbal raw materials are notoriously difficult to standardize because their chemistry depends on species, geography, harvest conditions and processing, and adulteration or mislabeling is a persistent problem in high-value markets. The study’s authors argue that their systematic workflow, combining qualitative volatile profiling by SPME-GC/MS, quantitative marker analysis by GC-FID, and safety screening for metals and pesticides, provides a template that can be adapted to other botanical and herbal materials. In effect, they have demonstrated a complete chain of evidence, from what a sample smells like at the molecular level to exactly how much of the key marker it contains to whether it is safe, all captured in validated instrumental measurements.

For a commodity that has been traded for centuries largely on trust, reputation and the trained senses of a few experts, the arrival of a validated chemical grading method marks a quiet but consequential shift. If eudesmol isomer content becomes an accepted benchmark, buyers could verify shipments against certificates of analysis, producers could optimize cultivation and resin-induction techniques against a measurable target, and regulators could police the market with defensible data rather than disputed opinions. The fragrance of agarwood may remain as mysterious and alluring as ever, but the question of whether a given batch is genuinely good is now, at last, something a machine can answer with a number.

Subject of Research: Objective quality evaluation of agarwood resin using eudesmol isomer quantification by gas chromatography

Article Title: Quality evaluation of agarwood achieved through the GC–FID-based quantification of eudesmol isomers identified via SPME–GC/MS

Article References: Quality evaluation of agarwood achieved through the GC–FID-based quantification of eudesmol isomers identified via SPME–GC/MS. (n.d.). https://doi.org/10.1007/s10068-026-02310-w

Image Credits: AI Generated

DOI: 10.1007/s10068-026-02310-w

Keywords: agarwood, eudesmol, sesquiterpenes, GC-FID, SPME-GC/MS, quality evaluation, Aquilaria, volatile compounds, food science, analytical chemistry, botanical raw materials, heavy metals