Thymus zygis EO
THYMUS ZYGIS ESSENTIAL OIL (THYMOL TYPE / SPANISH THYME OIL)
Monograph (modeled on ISO-style essential oil standards, including ISO 19817:2017 — Essential oil of thyme [Thymus vulgaris L. and Thymus zygis L.], thymol type)1. IdentificationBotanical name: Thymus zygis Loefl. ex L. (including subsp. gracilis (Boiss.) R. Morales and related taxa).
Family: Lamiaceae (Labiatae).
Common names: Spanish thyme, Red thyme (crude), White thyme (rectified), Tomillo rojo/blanco.
Plant part used: Flowering aerial parts (herb tops). Note: Commercial thymol-type thyme oil is commonly produced from T. zygis, T. vulgaris, or mixtures of both species.
Origin and Habitat
Native to the Iberian Peninsula (Spain and Portugal). It grows wild in Mediterranean scrublands on dry, stony, calcareous soils and is extensively cultivated in Spain for essential oil production.
Production Method
Obtained by steam distillation of the fresh or partially dried flowering aerial parts. Yield typically 0.5–5% (w/w), highest during full flowering. Crude oil is often reddish (“red thyme”); rectified versions are paler (“white thyme”).
Physical Characteristics (per ISO 19817:2017)
- Appearance: Mobile (clear) liquid.
- Colour: Yellow to red (crude oil).
- Odour: Strongly aromatic, phenolic (thymol-like), spicy.
- Relative density (d₂₀²⁰): 0.910–0.937.
- Refractive index (n_D²⁰): 1.494–1.504.
- Optical rotation (α_D²⁰): −6° to 0°.
- Solubility: 1 volume in a maximum of 3 volumes of 80% (v/v) ethanol at 20°C (may show slight opalescence).
Chemical Composition / Chromatographic Profile
Thymus zygis oil is typically a thymol chemotype. The chromatographic profile must conform to ISO 19817:2017 (and aligned Ph. Eur. requirements):
Characteristic components (percentage ranges per ISO 19817:2017):
- α-Thujene: 0.2–1.5%
- β-Myrcene: 1.0–3.0%
- α-Terpinene: 0.9–2.6%
- p-Cymene: 14.0–28.0%
- γ-Terpinene: 4.0–12.0%
- Linalool: 0.5–6.5% (or 1.5–6.5% in some references)
- Terpinen-4-ol: 0.1–2.5%
- Thymol: 37.0–55.0% (commonly 35–55%)
- Carvacrol: 0.5–5.5%
- Carvacrol methyl ether: 0.05–1.5%
- β-Caryophyllene: typically present (additional limits in older ISO 14715)
Typical chemotype: Thymol-rich phenolic type, with p-cymene and γ-terpinene as major biosynthetic precursors. Over 30–50 compounds may be identified by GC-MS, with monoterpene hydrocarbons and oxygenated monoterpenes dominant. Composition varies with chemotype (thymol vs. carvacrol), harvest season, subspecies, and origin. Analysis by GC-MS according to ISO 11024.
Storage and Stability
Store in tightly sealed, preferably dark glass or approved containers, protected from heat, light, and air (per ISO/TS 210). Shelf life is typically 2–3 years under cool, proper conditions. Phenolic content provides good stability, but monitor for changes.
Uses and Properties (Summary)
Traditionally used in Spain for respiratory conditions (coughs, bronchitis), digestive support, and as an antiseptic. Modern applications include aromatherapy, flavoring (food), fragrance, oral care products, and topical formulations. The oil exhibits strong antimicrobial (antibacterial, antifungal), antioxidant, and expectorant properties, primarily attributed to thymol and carvacrol.
Safety and Precautions
- High phenolic content (thymol/carvacrol): skin irritant and potential sensitizer. Always dilute properly (typically ≤1–2% for topical use). Perform patch tests.
- Avoid undiluted application, eyes, and mucous membranes.
- Use with caution or avoid during pregnancy, breastfeeding, in young children, and in individuals with hypertension, epilepsy, or sensitive skin. Consult a qualified practitioner.
- Generally regarded as safe at food/flavor use levels.
- Refer to current SDS, IFRA guidelines (for fragrance use), and regulatory standards (e.g., Ph. Eur., FDA, EMA).
References and Analytical Methods
- ISO 19817:2017 (Essential oil of thyme, thymol type).
- European Pharmacopoeia monograph (Thyme oil, thymol type).
- Older standard: ISO 14715 (Oil of thyme containing thymol, Spanish type).
- GC-MS with retention indices (ISO 11024).
- Scientific literature on T. zygis from Spain, Portugal, and Morocco.
This monograph compiles factual information from ISO, pharmacopoeial, and peer-reviewed sources. Natural essential oils show batch-to-batch and geographic variation; for compliance, regulatory, or certification purposes, always rely on batch-specific Certificates of Analysis and current standards.