Terpenes and Triterpenic Acids

1. What This Class of Substances Is

Terpenes and triterpenic acids are secondary plant compounds with an isoprenoid basic structure. They include monoterpenes (e.g., in essential oils), diterpenes (such as those in ginkgo), triterpenes (e.g., boswellic acids, ginsenosides), and tetraterpenes (carotenoids). Triterpenic acids such as ursolic acid or oleanolic acid are found in resins, roots, or fruits. Many of these substances act via modulation of enzymes (e.g., 5-lipoxygenase), receptors (e.g., PPAR-γ), or signalling pathways (NF-κB, MAPK). Their lipophilicity enables membrane interactions but also complicates bioavailability and standardisation in studies.

The effects in humans are difficult to measure, as terpenes often form complex metabolites and are metabolised differently in each individual. While laboratory and animal studies show clear effects (e.g., anti-inflammatory activity), clinical trials frequently fail due to challenges in dose-finding, placebo effects, or short observation periods. Furthermore, many terpenes are present in foods, which complicates the distinction from other dietary factors. Controlled studies with clear endpoints (e.g., inflammatory markers) are therefore rare but essential for valid conclusions.

2. Which Materials Are Included

All substances in the database for which this mechanism of action is described—ordered by the extent of human testing. The numbers represent studies per type of investigation.

3. How Robust the Evidence Is

Particularly well-documented are frankincense (Boswellia), adaptogens (e.g., ginseng, ashwagandha), and black cumin (Nigella sativa), each with over 20 controlled human studies. Ginger and turmeric/curcumin follow with 9 and 5 controlled studies, respectively. Other substances such as humic acid complexes, olive polyphenols, or anthocyanins show promising laboratory and animal findings but lack clinical data. The discrepancy is especially striking for green tea EGCG or resveratrol: despite high laboratory activity, controlled human studies are almost entirely absent.

These substances share common mechanisms of action, such as anti-inflammatory effects, antioxidant activity, or modulation of the microbiome. Many terpenes interact with similar signalling pathways (e.g., NF-κB), suggesting the transferability of findings. For example, boswellic acids and curcumin show synergistic effects in laboratory and animal studies, yet controlled trials on their combination in humans are lacking. The interaction with the gut microbiome is also plausible for many terpenes but has scarcely been systematically investigated. This presents potential for comparative studies.

4. Key Human Studies

• 1 A Randomised, Double-Blind, Placebo-Controlled, Crossover Study Examining the Hormonal and Vitality Effects of Ashwagandha (Withania somnifera) in Aging (2019) — Adaptogens
• 2 Ginseng for cognition (2010) — Adaptogens
• 3 A standardised Ashwagandha root extract alleviates stress, anxiety, and improves quality of life in healthy adults by modulating stress hormones: Results of a randomised, double-blind, placebo-controlled trial (2023) — Adaptogens
• 4 A double-blind, randomised, placebo-controlled study of the efficacy and safety of 5-Loxin® for treatment of osteoarthritis of the knee (2008) — Frankincense (Boswellia)
• 5 Anti-inflammatory and anti-cancer activities of frankincense: Targets, treatments and toxicities (2022) — Frankincense (Boswellia)
• 6 Boswellia serrata acts on cerebral oedema in patients irradiated for brain tumours: A prospective, randomised, placebo-controlled, double-blind pilot trial (2011) — Frankincense (Boswellia)
• 7 Review on clinical trials of black seed (Nigella sativa) and its active constituent, thymoquinone (2017) — Black cumin (Nigella sativa)
• 8 A phase I clinical trial to evaluate the safety of thymoquinone-rich black cumin oil (BlaQmax®) in healthy subjects: Randomised, double-blinded, placebo-controlled study (2022) — Black cumin (Nigella sativa)
• 9 Individual ingredients of NP-101 (thymoquinone formula) inhibit SARS-CoV-2 pseudovirus infection (2024) — Black cumin (Nigella sativa)
• 10 Antioxidant activity of ginger extract as a daily supplement in cancer patients receiving adjuvant chemotherapy: A pilot study (2017) — Ginger
• 11 The effects of ginger and its constituents in the prevention of metabolic syndrome: A review (2022) — Ginger
• 12 Hemp seed oil in association with β-caryophyllene, myrcene and ginger extract as a nutraceutical integration in knee osteoarthritis: A double-blind, randomised, placebo-controlled trial (2023) — Ginger
• 13 Efficacy and safety of curcumin and its combination with boswellic acid in osteoarthritis: A comparative, randomised, double-blind, placebo-controlled study (2018) — Turmeric and curcumin
• 14 The Use of Herbal Medicine in Sudden Sensorineural Hearing Loss in Diabetic Patients (2023) — Turmeric and Curcumin
• 15 Efficacy and Safety Evaluation of Boswellia serrata and Curcuma longa Extract Combination in the Management of Chronic Lower Back Pain: A Randomised Trial (2025) — Turmeric and Curcumin
• 16 Nutrients and Functional Components of Medicine-Food Homologous Substances on Antidepressant Effects: A Mechanism-Oriented Review (2026) — Gut Microbiome
• 17 Immune Metabolic Restoration in Systemic Lupus Erythematosus: The Impact of Gut Microbiota, Probiotics, and Nutritional Synergy (2025) — Gut Microbiome
• 18 Unveiling Acne Microbiome Signatures: The Role of the Microbiome and the Impact of a Facewash Formula Containing Plant-Derived Monoterpenes (2025) — Gut Microbiome
• 19 A Combination of Essential Fatty Acids, Panax Ginseng Extract, and Green Tea Catechins Modifies Brain fMRI Signals in Healthy Older Adults (2018) — Green Tea and EGCG
• 20 Current Nutritional and Pharmacological Approaches for Attenuating Sarcopenia (2023) — Green Tea and EGCG
• 21 Natural Products in Breast Cancer: Mechanistic Insights and Translational Potential for Treatment and Prevention (2026) — Green Tea and EGCG
• 22 Olive Leaves as a Potential Phytotherapy in the Treatment of COVID-19 Disease: A Mini-Review (2022) — Olive Polyphenols (Hydroxytyrosol)
• 23 Cardioprotective Potential of Oleuropein, Hydroxytyrosol, Oleocanthal and Their Combination: Unravelling Complementary Effects on Acute Myocardial Infarction (2024) — Olive Polyphenols (Hydroxytyrosol)
• 24 Exploring the Impact of Olive-Derived Bioactive Components on Gut Microbiota: Implications for Digestive Health (2025) — Olive Polyphenols (Hydroxytyrosol)

5. Open Questions

• Assessing Synergies: Are there clinically relevant interactions between terpenes (e.g., Boswellia + curcumin) or with other substance classes (e.g., humic acid complexes)?
• Optimising Bioavailability: How can lipophilic terpenes (e.g., ginsenosides) be standardised for controlled studies without altering their effects?
• Long-Term Effects: Which terpenes demonstrate sustained effects on inflammatory markers or the microbiome—and how long do these effects last?
• Dose-Response Relationship: For which terpenes (e.g., black cumin thymoquinone) is the therapeutic window sufficiently established in humans?
• Microbiome Interaction: How do terpenes alter the gut microbiome—and, conversely, how does the microbiome influence their metabolism?
• Combination with Standard Therapies: Can terpenes (e.g., adaptogens) exert supportive effects in the therapy of chronic diseases without causing interactions?

See also the gap list across all substances. This page is recalculated with each harvest.