Catalpol (Iridoid Glycoside · Neuroprotective · Anti-neurodegenerative · Anti-diabetic)

Compound	Catalpol
Chemical class	Terpenoid — Iridoid Glycoside (Epoxy-iridoid)
CAS	2415-24-9
Primary source	Rehmannia glutinosa (Chinese foxglove / Rehmannia), Catalpa spp., Plantago spp.
Key applications	Neuroprotective, anti-neurodegenerative, hepatoprotective, anti-diabetic
Claim strength	Moderate
Typical form	Rehmannia glutinosa liquid extract (water-soluble); catalpol isolate
Buy from Herbuno	Chinese Foxglove Liquid Extract (Water Soluble) - Rehmannia glutinosa →

Name origin: From Catalpa (catalpa tree genus), one of the early characterisation sources. Catalpol is structurally related to aucubin but contains an additional epoxide group, giving it distinct and generally more potent neuroprotective properties. Traditional use: Rehmannia glutinosa (Di Huang in TCM, Sheng Di Huang fresh / Shu Di Huang processed) is one of the most important herbs in Traditional Chinese Medicine, used for thousands of years for kidney yin deficiency, blood insufficiency, cognitive decline, diabetes, and anti-ageing. Catalpol is the primary iridoid glycoside and a key bioactive. Research trajectory: Catalpol has an extensive preclinical evidence base for neuroprotection in Parkinson’s disease, Alzheimer’s disease, and ischaemia models; hepatoprotective activity; anti-diabetic effects (AMPK activation, insulin sensitisation); and anti-ageing properties. Small human clinical data from Rehmannia extract preparations are emerging. Commercial source: Rehmannia Root Liquid Extract (water-soluble) from Herbuno provides catalpol as the primary iridoid constituent. See sourcing options below.

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Evidence for Catalpol Applications

Neuroprotection — Parkinson’s disease models: Catalpol is one of the most extensively studied botanical neuroprotectants in PD animal models. It reduces dopaminergic neuron loss in 6-OHDA and MPTP models, decreases α-synuclein aggregation, activates Nrf2/HO-1 antioxidant pathway, and inhibits neuroinflammation (NF-κB, NLRP3). Multiple Chinese research groups have confirmed these findings. Human data are limited to Rehmannia complex preparations. Claim strength: Moderate (convergent preclinical; no direct human RCT).

Alzheimer’s disease models: Catalpol reduces amyloid-beta aggregation, inhibits tau hyperphosphorylation (GSK-3β pathway), and reduces neuroinflammation in AD animal models. Activates Nrf2 and SIRT1, relevant to longevity and neuroprotection formulation positioning. Claim strength: Moderate (preclinical convergent).

Anti-diabetic (AMPK/insulin sensitisation): Catalpol activates AMPK and improves insulin sensitivity in diabetic animal models. Reduces fasting blood glucose and HbA1c in streptozotocin-induced diabetic rats. Rehmannia extract preparations have small human pilot data for blood glucose management in TCM clinical contexts. Claim strength: Moderate.

Hepatoprotective: Catalpol protects against CCl4-induced liver injury, reduces hepatic oxidative stress, and inhibits inflammatory pathways. Complementary to aucubin in hepatoprotective formulations with overlapping but distinct mechanisms. Claim strength: Moderate.

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Dosage & Formulator Specification

No established human clinical dose for isolated catalpol. Traditional TCM Rehmannia root dose: 9–30 g/day dried root (as part of compound prescriptions). Catalpol content in processed Rehmannia (Shu Di Huang) is typically 0.05–0.1% — processing reduces catalpol content versus fresh root. For catalpol-optimised preparations, specify fresh or minimally processed Rehmannia extract (higher catalpol). Animal neuroprotective doses extrapolate to approximately 10–50 mg/day catalpol for a 70 kg human — achievable via concentrated Rehmannia extract but not established in clinical trials. Herbuno’s Rehmannia Root Liquid Extract (water-soluble) should be characterised by HPLC for catalpol content.

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Frequently Asked Questions — Catalpol

Is Rehmannia the only commercial source of catalpol?
Rehmannia glutinosa is the primary commercial source of catalpol at supplement-relevant concentrations. Catalpol also occurs in Plantago species (alongside aucubin), Catalpa species, and some Veronica species, but none have been developed as commercial catalpol extraction sources. For supplement applications, Rehmannia root extract is the appropriate and well-characterised source.

What is the difference between raw (Sheng Di Huang) and processed (Shu Di Huang) Rehmannia?
Raw Rehmannia (Sheng Di Huang) is the fresh or dried root, higher in catalpol and other iridoids, with properties described in TCM as clearing heat and cooling blood. Processed Rehmannia (Shu Di Huang) is wine-steamed, which converts iridoids and changes the TCM character toward nourishing yin and blood, with reduced catalpol content. For catalpol-optimised formulations, raw Rehmannia extract is preferred; processed Rehmannia is used for TCM tonification applications.

Is catalpol relevant for Parkinson’s disease supplement formulations?
The convergent preclinical evidence for catalpol in PD models (dopaminergic neuron protection, α-synuclein inhibition, Nrf2 activation) is among the stronger botanical evidence bases for neuroprotection targeting Parkinson’s disease mechanisms. For supplement contexts, position as "studied to support healthy dopaminergic neuron function" or "preclinical evidence for neuroprotective activity" — do not make Parkinson’s disease therapeutic claims without human clinical trial substantiation.

Can catalpol be combined with other neuroprotectants?
Yes — catalpol is rationally combined with other compounds targeting complementary neuroprotective mechanisms: with aucubin (complementary iridoid neuroprotection from Plantago), with curcumin (NF-κB and amyloid-beta targeting), with resveratrol (SIRT1/AMPK activation), and with lion’s mane mushroom (NGF stimulation). None of these combinations have specific human trial evidence; the rational basis is complementary mechanisms across neuroprotective pathways.

Related compounds: Aucubin, Geniposide, Harpagoside, Borneol

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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