Part VI. Vietnamese essential oils: composition and chemotypes

This part brings together peer-reviewed analyses of samples collected in Vietnam and compares them with international standards where these exist. One methodological caveat governs how the whole part should be read: most Vietnamese papers report GC-MS peak-area percentages without response-factor correction, usually with only one sample per site and rarely with lot numbers. The figures below are snapshots of one place at one time, not commercial ranges.

6.1 Summary table

6.2 Deviations from international standards

Figure 5 places four Vietnamese parameters beside the international reference ranges.

Cassia. Vietnamese cassia bark oil contains 93–96% trans-cinnamaldehyde, above the 88% ceiling of ISO 3216:1997 (TCVN 6029:2008; the text of the standard could be read only in part), and o-methoxycinnamaldehyde is not reported in the bark-oil analyses read (only 0.36% in twig-and-leaf oil), whereas the standard requires 3–15% Measured. There are two possible explanations Inference: the standard was built for Chinese-style twig-and-leaf oil, so bark oil is not the same type of product; or uncorrected peak-area percentages inflate the main constituent. Either way, Vietnamese cassia bark oil may not match the ISO 3216 chromatographic profile even when its sensory quality is high. A “meets ISO” label should state clearly which standard it was checked against.

On the species: the samples in the table are recorded by their authors as C. cassia. The international literature on coumarin (Part III) reports high levels in C. loureiroi, a species that also occurs in Vietnam. The two species are different, and identification in trade is not always consistent. None of the sources read quantifies coumarin in Vietnamese cassia essential oil; the figure of 76.1 g/kg refers to bark, not to oil. This is an important gap, because coumarin is restricted in food and must be labelled in cosmetics.

Lemongrass. TCVN 11425:2016 (equivalent to ISO 3217) requires a carbonyl content, expressed as citral, of ≥ 75%. Two of the four Phu Tho samples had total GC citral below this level; an evaluation of 5 lemongrass germplasm sources in Ha Noi also concluded that the citral of lemongrass was below ISO 3217, while East Indian lemongrass (sả dịu) C. flexuosus was above ISO 4718 Measured (Tạp chí Khoa học Công nghệ Nông nghiệp Việt Nam 2022, abstract). The two methods differ (GC percentage and carbonyl titration), but both point in the same direction: Vietnamese lemongrass tends to sit at the lower limit of the standard.

Cajuput. The most important finding of this branch: Vietnamese cajuput is not uniformly a 1,8-cineole type Measured. An analysis of six sites in southern Vietnam (one sample per site) separated two groups: a monoterpene group containing cineole (Long An 7.3%, Tay Ninh 23.0%) and a cineole-free, sesquiterpene-rich group (Dong Thap, Phu Quoc, U Minh Thuong, Ba Ria–Vung Tau) (Agriculturae Conspectus Scientificus 2019; Figure 6). In central Vietnam, cineole is higher: 47.0% (Tạp chí KH&CN ĐH Công nghiệp Hà Nội 2023, abstract), 30.9% at Phong Dien and 25.4% at Huong Tra, Hue (Tạp chí Phân tích Hóa, Lý và Sinh học 2020, abstract); the number of samples at the central sites is not stated.

The Tram Chim (Dong Thap) sample contained 48.3% methyl eugenol and 34.5% methyl isoeugenol, which is unusual for M. cajuputi; species identification should be checked before these data are used for commercial purposes Inference. There is no ISO or TCVN for Vietnamese cajuput oil, and no peer-reviewed paper on cajuput from Quang Tri.

Star anise. The Cao Bang sample had 0.42% estragole, lower than the roughly 2% level in an international review (Sharafan et al. 2022, doi:10.3390/molecules27030650). This is a safety advantage but rests on a single sample; cis-anethole in Vietnamese star anise has no data (NR). Illicium verum must be distinguished from the toxic Japanese star anise I. anisatum: the signal for anisatin, a convulsant, is about 250 times higher in I. anisatum than in I. verum (Schrage et al. 2013, doi:10.1016/j.chroma.2013.07.072; abstract only read). Anisatin is non-volatile, so it must be tested in the fruit, not in the oil Inference.

6.3 Notable chemotypes

• Ocimum: African basil (hương nhu trắng) is consistently a eugenol type (80–83%, measured in 2007 and 2022); holy basil (hương nhu tía) is a methyl eugenol type (46%). Methyl eugenol is restricted by IFRA (Part VII), so the two cannot substitute for each other from a safety standpoint.
• Litsea: citral is concentrated in the fruit and stem bark; the leaves are a cineole or sabinene type. Commercial fruit oil should contain about 65–71% citral according to the Vietnamese samples Inference.
• Camphor tree: Vietnam has a linalool type (linalool above 91% in the leaves), unlike the common picture of camphor tree as camphor-rich. Camphor, cineole and borneol types in Vietnam have no data (NR).
• Ginger: the two samples from Nghe An and Phu Yen differ completely (zingiberene 30.8% versus none); this may be due to cultivar or misidentification of the species and needs verification.
• Pomelo peel (C. maxima, pomelo): limonene 89–94%; the trace constituents that may carry the characteristic odour (nootkatone, long-chain aldehydes) have not been analysed in Vietnamese pomelo. Note: the thiol and nootkatone data in Parts II–III are for grapefruit (C. paradisi), a different species.

6.4 Agarwood: distilled oil does not reflect the wood

Cultivated A. crassna agarwood from three regions gave an oil yield of only 0.25–0.32% after 72 hours of distillation, with neopetasane, β-agarofuran, jinkoh-eremol and agarospirol as the main constituents Measured (Processes 2019). Chromones, the main markers for distinguishing natural from cultivated agarwood, barely pass into distilled oil and must be analysed by LC-MS on the wood or an extract. Studies distinguishing by chromones exist so far only for Chinese A. sinensis (Li et al. 2016, doi:10.3390/ijms17050771; abstract). We have not found any peer-reviewed study comparing natural and cultivated agarwood for Vietnamese A. crassna.

6.5 Sassafras-type oil: composition and legal status only

Oil from the wood of wild Vietnamese xá xị trees contains about 90% safrole. Safrole is listed in Table I of the 1988 United Nations Convention on precursors according to the INCB Red List, 23rd edition (2025), which one branch was able to read Standard; another branch could not verify this directly from the description page; IFRA prohibits safrole, isosafrole and dihydrosafrole as fragrance ingredients, with the total of the three in the finished product ≤ 0.01%. In Vietnam, the precursor list under Decree 57/2022/ND-CP has been replaced by Decree 28/2026/ND-CP (only Article 3 has been read so far); the annex containing the list could not be read, so the position of safrole in the list is not confirmed (NR). Recommendation Inference: do not trade xá xị or vù hương essential oil; require certificates of analysis stating safrole content for Cinnamomum essential oils of unclear origin.

6.6 Data gaps

1. Fujian cypress (pơ mu) Fokienia hodginsii wood oil: no peer-reviewed analysis; the only data (a 1993 book, via a secondary source) contradict the commercial description of it as nerolidol-rich.
2. Coumarin in Vietnamese cassia oil; cis-anethole in Vietnamese star anise oil.
3. Flower oils: white champaca, frangipani and jasmine collected in Vietnam.
4. Multi-lot, multi-season data for every species: almost all data are one sample per site.

A monograph compiled from 718 sourced facts collected under a common protocol and cross-checked independently. Items labelled Inference are the compilers’ own judgements. Diagrams are newly drawn from published data. Scientific reference material — not legal or medical advice, and no substitute for the text of the standards.