Teak

Tectona grandis leaf extracts contain the diterpenes (+)-Eperua-8,13-dien-15-oic acid and (+)-Eperua-7,13-dien-15-oic acid, alongside phenolics, flavonoids, and tannins, which act through inhibition of 5α-reductase, suppression of pro-inflammatory cytokines, and free-radical scavenging. In vitro studies demonstrate that the leaf extract inhibits 5α-reductase with an IC₅₀ of 9.57 ± 0.09 μg/mL and suppresses IL-6 production in LPS-stimulated macrophages with an IC₅₀ of 6.554 ± 0.277 μg/mL, suggesting potential applications in androgenetic alopecia and inflammatory conditions.

Origin & History

Tectona grandis L.f. is native to the tropical forests of South and Southeast Asia, with its natural range spanning Myanmar, Thailand, Laos, and India, and it has been extensively cultivated across Java, Indonesia, and other equatorial regions for centuries. The tree thrives in well-drained, fertile soils at elevations up to 1,000 meters, requiring distinct wet and dry seasons for optimal growth. Traditionally regarded as a premium timber species, teak plantations have expanded across tropical Africa and Latin America, though medicinal research has focused primarily on wild and plantation-grown specimens from Thailand and Indonesia.

Historical & Cultural Context

Tectona grandis occupies a position of extraordinary cultural and economic importance across South and Southeast Asia, where it has been cultivated for over two millennia primarily as a premier hardwood timber prized for shipbuilding, temple construction, and royal architecture in Myanmar, Thailand, and India. In Thai traditional medicine, the leaves have been employed as a topical remedy for wound healing, with the astringent tannins and resinous compounds serving as natural antimicrobials and tissue-protective agents, a practice that aligns with the documented phytochemical profile of the leaves. Tectoquinone, a naturally occurring anthraquinone in teak heartwood, has been noted as a bioactive marker associated with the wood's legendary durability and has attracted interest in pharmacological research as a result of its structural pharmacophore. The tree holds religious significance in Hindu and Buddhist traditions, frequently planted near temples and used in sacred ceremonies, and its association with longevity and structural integrity has historically extended—by cultural analogy—to folk attributions of medicinal strength.

Health Benefits

- **5α-Reductase Inhibition (Androgenetic Alopecia)**: The leaf extract inhibits the enzyme 5α-reductase with an IC₅₀ of 9.57 ± 0.09 μg/mL in vitro; the isolated diterpenes (+)-Eperua-8,13-dien-15-oic acid (IC₅₀ 14.19 ± 2.87 μM) and (+)-Eperua-7,13-dien-15-oic acid (IC₅₀ 14.65 ± 0.31 μM) are the principal active agents, offering a potential botanical alternative for DHT-mediated hair loss.
- **Anti-Inflammatory Activity**: Ethanolic leaf extracts suppress nitric oxide production in LPS-induced RAW 264.7 macrophages (IC₅₀ 12.100 ± 0.885 μg/mL) and inhibit the pro-inflammatory cytokines IL-1β (IC₅₀ 8.365 ± 0.520 μg/mL) and IL-6 (IC₅₀ 6.554 ± 0.277 μg/mL), indicating broad innate immune modulation.
- **Antioxidant Protection**: Mature leaf extracts exhibit the highest antioxidant capacity, attributed to phenolic compounds (8.751 ± 0.018 mg GAE/g DW), flavonoids (0.359 ± 0.017 mg QE/g DW), and condensed tannins (0.303 mg CE/g DW) including quercetin and gallic acid, which scavenge reactive oxygen species and reduce oxidative stress.
- **Wound Healing Support (Traditional)**: Thai traditional medicine employs teak leaves topically for wound management, with the tectoquinone content and astringent tannins contributing to tissue protective and antimicrobial actions that may facilitate skin barrier repair.
- **Antibacterial Activity**: Ethyl acetate and ethanolic leaf extracts containing alkaloids (3.72–4.16%), tannins (2.16–3.72%), and saponins (1.45–1.83%) have demonstrated activity against respiratory bacterial pathogens in preliminary phytochemical validation studies, suggesting a role in traditional respiratory infection management.
- **Hepatoprotective and Cytoprotective Potential**: GC-MS profiling has identified phytol and n-decanoic acid in leaf extracts; phytol is a known inducer of antioxidant and anti-apoptotic pathways, and compound 2 (Eperua-7,13-dien-15-oic acid) maintains greater than 80% cell viability at concentrations up to 100 μg/mL, supporting a favorable cytotoxic safety margin.
- **Termicidal and Antifungal Defense Compounds**: Heartwood extractives including lariciresinol, tectonoelins A and B, and anthraquinones confer resistance to wood-degrading fungi and termites; these same compounds show preliminary bioactivity in microbiological assays, pointing to potential antimicrobial applications beyond timber preservation.

How It Works

The primary mechanistic axis of Tectona grandis leaf bioactivity centers on competitive inhibition of 5α-reductase, the enzyme responsible for converting testosterone to dihydrotestosterone (DHT); the diterpenes (+)-Eperua-8,13-dien-15-oic acid and (+)-Eperua-7,13-dien-15-oic acid are the principal inhibitors with IC₅₀ values of approximately 14.2 and 14.7 μM, respectively, positioning them comparably to phytochemical 5α-reductase inhibitors already in dermatological research. Anti-inflammatory effects are mediated through suppression of the NF-κB-dependent inflammatory cascade: the ethanolic extract reduces LPS-induced nitric oxide synthesis (IC₅₀ 12.10 μg/mL), likely by downregulating inducible nitric oxide synthase (iNOS), and independently curtails IL-1β and IL-6 secretion in RAW 264.7 macrophages, indicating inhibition at the level of cytokine transcription or post-translational processing. The antioxidant mechanism involves direct radical scavenging by polyphenols—particularly quercetin and gallic acid—which donate hydrogen atoms to neutralize reactive oxygen species, and indirect protection through chelation of redox-active metal ions by condensed tannins. Phytol, a diterpene alcohol identified by GC-MS, may contribute through activation of peroxisome proliferator-activated receptor-alpha (PPAR-α), modulating lipid metabolism and reinforcing cytoprotective gene expression.

Scientific Research

The available evidence base for Tectona grandis leaf bioactivity is entirely preclinical, comprising in vitro enzyme inhibition assays, macrophage cell-line models (RAW 264.7), and phytochemical characterization studies, with no published human clinical trials or controlled animal intervention studies identified as of the latest literature review. Insumrong et al. (2022) provided the most pharmacologically detailed dataset, reporting IC₅₀ values for 5α-reductase inhibition, nitric oxide suppression, and cytokine inhibition from isolated diterpenes and crude ethanolic extracts, but the study design precludes extrapolation of effective doses to humans. Phytochemical screening studies from Indonesian and Thai research groups have quantified phenolic, flavonoid, and tannin contents using standardized colorimetric assays and confirmed trace heavy metal safety (Cd 0.001–0.004 mg/kg; As 0.012–0.018 mg/kg; Pb undetectable), adding regulatory-relevant safety data. The overall evidence level is preliminary; while the mechanistic rationale is scientifically coherent, translation to clinical efficacy requires dose-escalation pharmacokinetic studies, in vivo animal trials, and ultimately randomized controlled human trials before any therapeutic claims can be substantiated.

Clinical Summary

No human clinical trials evaluating Tectona grandis leaf extracts for any indication have been published in the accessible literature. All quantified outcomes originate from in vitro systems: the most clinically relevant findings are 5α-reductase inhibition (extract IC₅₀ 9.57 μg/mL) and IL-6 suppression (IC₅₀ 6.554 μg/mL) in cell-based assays, which provide proof-of-concept but cannot be directly converted to human dosing guidance. The absence of pharmacokinetic data—including oral bioavailability, first-pass metabolism of the active diterpenes, and tissue distribution—represents a critical gap that prevents clinical translation. Confidence in the reported in vitro results is moderate for assay validity but very low for predicting human therapeutic outcomes; the ingredient should be classified as a research-stage botanical pending in vivo confirmation.

Nutritional Profile

Tectona grandis leaves are not consumed as a food source and have no established nutritional value as a macronutrient or micronutrient contributor to the human diet. The primary bioactive constituents are secondary metabolites: total phenolics at 8.751 ± 0.018 mg GAE/g DW, total flavonoids at 0.359 ± 0.017 mg QE/g DW, and condensed tannins at 0.303 ± 0.000 mg CE/g DW in mature leaf ethanolic extracts. GC-MS analysis of leaf volatile and semi-volatile fractions identifies phytol (a diterpene alcohol with PPAR-α activity), n-decanoic acid (a medium-chain saturated fatty acid with antimicrobial properties), and heptadecenal (a fatty aldehyde). Heartwood sugars include glucose at 43.7–44.6 wt.%, which is relevant to the wood's industrial processing but not to medicinal applications. Bioavailability of the leaf polyphenols and diterpenes has not been characterized in vivo; lipophilicity of the diterpene acids suggests potential for enhanced absorption with fatty meal co-administration, but this remains untested.

Preparation & Dosage

- **Ethanolic Leaf Extract (Research Grade)**: Prepared by macerating dried mature leaves in 70–95% ethanol; tested in vitro at concentrations of 50–100 μg/mL with acceptable cytotoxicity profile; no human dose established.
- **Ethyl Acetate Extract**: Yields higher flavonoid fractions (5.89–6.21%); used in antibacterial and phytochemical studies; no standardized human dosage available.
- **Microwave-Assisted Extraction (MAE)**: Emerging preparation method optimized for polyphenol yield from mature leaves; reported to improve extraction efficiency over conventional maceration; laboratory scale only.
- **Traditional Topical Application (Thai Medicine)**: Leaves are prepared as a poultice or decoction for direct wound application; specific ratios and preparation protocols are not formally documented in the reviewed literature.
- **Leaf Maturity Consideration**: Mature leaves consistently yield higher phenolic content (8.751 mg GAE/g DW) and antioxidant activity compared to young leaves; any preparation intended to maximize bioactivity should specify mature leaf material.
- **Standardization**: No commercial standardization percentages for diterpene or phenolic content have been established; research extracts are characterized by total phenolic, flavonoid, and tannin values per gram of dry weight.
- **Note**: No supplemental product formulations, capsule doses, or clinically validated dosing regimens exist for Tectona grandis in any reviewed source.

Synergy & Pairings

Based on shared mechanistic pathways, Tectona grandis leaf extract may exhibit additive or synergistic 5α-reductase inhibition when combined with saw palmetto (Serenoa repens) standardized to beta-sitosterol, as both target overlapping enzyme binding sites through distinct phytochemical classes (diterpene acids versus phytosterols), potentially allowing lower effective doses of each. The antioxidant polyphenol fraction—particularly quercetin and gallic acid equivalents—may be potentiated by co-administration with vitamin C (ascorbic acid), which regenerates oxidized flavonoid radicals and extends the functional half-life of phenolic antioxidants in biological systems. Anti-inflammatory synergy with curcumin (from Curcuma longa) is pharmacologically plausible given that both act on the NF-κB/iNOS/cytokine axis, though this specific pairing has not been experimentally validated for Tectona grandis.

Safety & Interactions

In vitro cytotoxicity assessments indicate a favorable safety margin: compound (+)-Eperua-7,13-dien-15-oic acid maintains greater than 80% cell viability in tested cell lines at concentrations up to 100 μg/mL, while the crude extract and compound 1 are non-toxic up to 50 μg/mL under the same conditions. Heavy metal analysis of ethanolic leaf extracts confirms cadmium (0.001–0.004 mg/kg), arsenic (0.012–0.018 mg/kg), and undetectable lead levels, all within internationally recognized safety thresholds, reducing concerns about contaminant-related toxicity. No human side effects, drug-drug interactions, or contraindications have been formally studied or reported in the available literature; however, given the 5α-reductase inhibitory activity, theoretical caution is warranted in individuals using finasteride, dutasteride, or hormonal therapies where additive androgenic pathway modulation may be clinically significant. Use during pregnancy and lactation cannot be assessed due to the complete absence of relevant safety data, and avoidance is the prudent recommendation until in vivo reproductive toxicology studies are conducted.