Antiplatelet

Danshensu’s mechanism is distinct from salvianolic acid B’s, which acts via P2Y12 antagonism, phosphodiesterase inhibition and direct thrombin-site binding, so the two are additive rather than redundant, and a danshen preparation delivers both.

In rats, danshensu reduced thrombus weight in two experimental thrombosis models, dose-dependently inhibited ADP- and arachidonic-acid-induced platelet aggregation in both normal and blood-stasis animals, and lowered blood viscosity, plasma viscosity and haematocrit.

The mechanism traced to selective inhibition of COX-2 but not COX-1 in the venous wall, with thromboxane B2 down, 6-keto-prostaglandin F1α up and the TXA2/PGI2 ratio normalised.

Unusually for a COX-active agent, it produced no gastric lesions and was protective against aspirin-induced ulceration at 60 mg/kg ^{4Reference 4Yu C et al. · 2014AnimalEffects of danshensu on platelet aggregation and thrombosis — in vivo arteriovenous shunt and venous thrombosis models in ratsView study →}.

A second, independent mechanism: danshensu induces SIRT1, lowers platelet ROS, prevents mitochondrial dysfunction and blocks release of platelet mitochondrial DNA, which otherwise activates platelets via DC-SIGN. It inhibited FeCl₃-induced carotid thrombosis in mice and did not prolong tail bleeding time ^{5Reference 5Xue Y et al. · 2022Danshensu prevents thrombosis by inhibiting platelet activation via SIRT1/ROS/mtDNA pathways without increasing bleeding riskView study →}.

The line is old: anticoagulative action was reported in 1983 ^{6Reference 6Li CZ · 1983Experimental study on the anticoagulative action of danshensu [in Chinese]View study →}, and the sodium salt’s effect on rabbit plasma prostacyclin and thromboxane A2 after coronary occlusion in 1986 ^{7Reference 7Zhu L et al. · 1986Effects of sodium beta-3,4-dihydroxyphenyl lactate and beta-phenyl lactic acid on prostacyclin and thromboxane A2 contents in the plasma of rabbits after coronary artery occlusion [in Chinese]View study →}.

Human relevance is anchored by a 14-subject crossover in which a danshen-containing product plus aspirin lowered systemic thromboxane B2, attributed partly to danshensu’s COX-2 inhibition ^{8Reference 8Zhang Y et al. · 2020Clinical trialIs it safe to take Radix Salvia miltiorrhiza – Radix Pueraria lobata product with warfarin and aspirin? A pilot study in healthy human subjectsView study →}.

The effect is additive with aspirin, clopidogrel, NSAIDs and anticoagulants, and relevant before surgery.

The “no increased bleeding” finding is one tail-bleeding assay in mice ^{5Reference 5Xue Y et al. · 2022Danshensu prevents thrombosis by inhibiting platelet activation via SIRT1/ROS/mtDNA pathways without increasing bleeding riskView study →}, not a safety clearance.

Parthenolide inhibits granule secretion and serotonin release from blood platelets and polymorphonuclear leucocytes, with a pattern distinct from the NSAIDs ^{15Reference 15Heptinstall S et al. · 1985In vitroExtracts of feverfew inhibit granule secretion in blood platelets and polymorphonuclear leucocytes — in vitroView study →}, and the effect tracks parthenolide content closely enough across authenticated and commercial feverfew that it was the bioassay used to justify parthenolide as the standardisation marker, “mainly responsible for the antisecretory effects of extracts of feverfew” ^{16Reference 16Heptinstall S et al. · 1992In vitroParthenolide content and bioactivity of feverfew (Tanacetum parthenium (L.) Schultz-Bip.): estimation of commercial and authenticated feverfew products — in vitroView study →}.

Isolated parthenolide also irreversibly abolishes contractile responses in rabbit aorta, consistent with covalent modification of a vascular target ^{17Reference 17Barsby RW et al. · 1992In vitroFeverfew extracts and parthenolide irreversibly inhibit vascular responses of the rabbit aorta — in vitroView study →}.

All of it is in-vitro human platelet or ex-vivo tissue work, and no study connects the active concentration to any achievable plasma level, which is why the bleeding caution attached to feverfew is theoretical rather than measured.

Sal A’s best-evidenced activity, and the only one with data generated on human cells.

In rats, intravenous Sal A (2.5-10 mg/kg) inhibited ADP-induced platelet aggregation dose-dependently and reduced thrombus weight in an arteriovenous shunt model, with raised cAMP in plasma and in ADP-activated platelets as the mechanism; agonist-stimulated aggregation (ADP, thrombin, arachidonic acid) fell on both rat and washed human platelets in vitro ^{18Reference 18Fan HY et al. · 2010Antiplatelet and antithrombotic activities of salvianolic acid AView study →}.

Five consecutive days of intravenous dosing left coagulation parameters unchanged ^{18Reference 18Fan HY et al. · 2010Antiplatelet and antithrombotic activities of salvianolic acid AView study →}, so the action is platelet-directed rather than anticoagulant.

The human-tissue result is more direct: platelets drawn from 40 patients with type 2 diabetes, a hyperreactive and antiplatelet-resistant population, and pre-incubated with Sal A showed reduced PAC-1 fibrinogen binding, reduced CD62p/P-selectin expression under both ADP and thrombin, and reduced maximal aggregation, with no attenuation in patients who already had diabetic complications ^{19Reference 19Zhou AM et al. · 2020Clinical trialSalvianolic acid A inhibits platelet activation and aggregation in patients with type 2 diabetes mellitusView study →}.

A related but distinct thread: Sal A blunted PDGF-BB-driven human smooth-muscle proliferation by inducing p21 through cAMP/PKA/CREB, reproduced in the neointima of balloon-injured rat arteries ^{20Reference 20Sun L et al. · 2016Prevention of vascular smooth muscle cell proliferation and injury-induced neointimal hyperplasia by CREB-mediated p21 induction — an insight from a plant polyphenolView study →}, the same cAMP node in a different cell type, pointing at restenosis rather than thrombosis.

The cAMP mechanism is unexplained.

No PDE-inhibition data exist, and whether cAMP rises by PDE inhibition or adenylyl cyclase activation is unresolved.

The best-attributed pharmacology this molecule has, and the reason it matters for safety before therapy.

Sal B inhibits human platelet activation induced by multiple agonists in vitro by two independently identified mechanisms, phosphodiesterase inhibition (dipyridamole’s mechanism) and P2Y12 receptor antagonism (clopidogrel’s target) ^{21Reference 21Liu L et al. · 2014Salvianolic acid B inhibits platelets as a P2Y12 antagonist and PDE inhibitor — evidence from clinic to laboratoryView study →}.

Separately, Sal B inhibits thrombin-induced platelet activation, reduces ADP- and collagen-induced aggregation, alters fibrin network structure and reduces thrombus formation in mouse cremaster arterioles, and binds the thrombin catalytic site directly, confirmed by enzymatic assay, intrinsic fluorescence spectrophotometry and isothermal titration calorimetry, with docking showing kinship to the trisubstituted benzimidazole inhibitors such as dabigatran.

The authors describe it as the first herb-derived direct thrombin catalytic-site inhibitor ^{22Reference 22Neves MAD et al. · 2024Salvianolic acid B inhibits thrombosis and directly blocks the thrombin catalytic siteView study →}.

In acute-coronary-syndrome patients already on clopidogrel plus aspirin, salvianolate (≈85% Sal B) significantly potentiated dual antiplatelet therapy on ADP-induced PAC-1 binding and P-selectin expression ^{21Reference 21Liu L et al. · 2014Salvianolic acid B inhibits platelets as a P2Y12 antagonist and PDE inhibitor — evidence from clinic to laboratoryView study →}, and a separate randomised PK/PD study in 18 CHD patients found salvianolate and aspirin interact pharmacokinetically, with Sal B elimination prolonged and its AUC reduced ^{23Reference 23Cao W et al. · 2021RCTDrug–drug interactions between salvianolate injection and aspirin based on their metabolic enzymes — randomised clinical trialView study →}.

These are preparation-level human results.

The effect is additive bleeding risk with aspirin, clopidogrel, DOACs and warfarin, and it is relevant before surgery.

Sal B inhibited shear-induced platelet aggregation dose-dependently in rat platelet-rich plasma under 15 Pa constant shear, additively with tetramethylpyrazine; aggregation fell from 48.6 ± 4.6% to 12.5 ± 2.1% for the combination ^{24Reference 24Li M et al. · 2004AnimalInhibition of shear-induced platelet aggregation in rat by tetramethylpyrazine and salvianolic acid BView study →}.

Reviews add fibrinolysis promotion and antithrombin-III-like activity at fraction level ^{25,26,27Reference 25Ho JH · 2011Salvianolic acids — small compounds with multiple mechanisms for cardiovascular protectionView study →Reference 26Du G et al. · 2020ReviewChemical and pharmacological research on the polyphenol acids isolated from Danshen — a review of salvianolic acidsView study →Reference 27Chan TY · 2001Interaction between warfarin and danshen (Salvia miltiorrhiza)View study →}.

This is the thread behind the warfarin warning.

Two independent in-vitro mechanisms, 33 years apart, never tested against each other.

Tussilagone inhibits platelet activation by blocking GPVI downstream signalling ^{29Reference 29Antiplatelet activity of tussilagone via · 2020In vitroFrontiers in Medicine. https://pubmed.ncbi.nlm.nih.gov/32850895/View study →}.

As L-652,469, the same molecule is a competitive PAF-receptor antagonist (Kᵢ 3.2–4.0 µM against [³H]PAF binding to rabbit platelet membranes, K_B 5.16 µM) that inhibited gel-filtered rabbit platelet aggregation with pA₂ 5.79 ^{30Reference 30Hwang SB et al. · 1987In vitroL-652,469 — a dual receptor antagonist of platelet activating factor and dihydropyridines from Tussilago farfara L. — in vitroView study →}.

In vivo, it attenuated atherosclerotic lesion formation in ApoE-deficient mice by suppressing MAPK-mediated macrophage inflammation ^{31Reference 31Shen S et al. · 2023Tussilagone attenuates atherosclerosis through inhibiting MAPKs-mediated inflammation in macrophagesView study →}.

There is one in-vitro study per mechanism plus one mouse model, no human antiplatelet data, and the two proposed mechanisms have never been reconciled.

Direct molecule-level evidence exists, which matters because danshen’s antiplatelet reputation is normally credited to the water-soluble salvianolic acids.

Dihydrotanshinone I inhibited collagen-induced aggregation of rabbit washed platelets with IC50 8.7 ± 5.6 µM, about sevenfold more potent than EGCG assayed alongside, by suppressing intracellular Ca²⁺ mobilisation and arachidonic-acid liberation, with a modest reduction in thromboxane B2 at 50 µM ^{9Reference 9Park JW et al. · 2008Park JW, Lee SH, Yang MK, et al. (2008). 15,16-dihydrotanshinone I, a major component from Salvia miltiorrhiza Bunge, inhibits rabbit platelet aggregation by suppressing intracellular calcium mobilization — ex vivo study. Archives of Pharmacal Research. https://pubmed.ncbi.nlm.nih.gov/18277607/View study →}.

The exposure arithmetic is unfavourable: 8.7 µM is roughly 200–700× the measured plasma Cmax ^{10Reference 10Zhang Y et al. · 2012ReviewTanshinones: sources, pharmacokinetics and anti-cancer activities — reviewView study →}.

The molecule has intrinsic antiplatelet activity; it is not established that any danshen preparation delivers enough of it to matter clinically.

The cleanest molecule-level finding among the tanshinones, and the one that carries the safety weight.

Tanshinone IIA selectively inhibited rat platelet aggregation induced by reversible ADP stimulation (3 µM) in a concentration-dependent manner over 0.5–50 µM, while being markedly less active against irreversible ADP (10 µM) and collagen (10 µg/mL).

Mechanistically it modulated tubulin acetylation and inhibited Erk-2 phosphorylation.

Given intraperitoneally at 10 mg/kg it prolonged mouse bleeding time by 58% (2.06 ± 0.29 min vs 1.30 ± 0.07), with aspirin as the reference drug ^{28Reference 28Maione F et al. · 2014In vitroTanshinone IIA, a major component of Salvia miltiorrhiza Bunge, inhibits platelet activation via Erk-2 signaling pathway — in vitro and mouse in vivo studyView study →}.

The bleeding caution for dan shen is therefore molecular as well as herb-level.

A small evidence base with disproportionate safety relevance.

Cryptotanshinone inhibits rat platelet aggregation in a concentration-dependent manner; the assignment of that effect to Gi-coupled P2Y12 receptor antagonism was made by molecular docking, not by a binding or functional receptor assay ^{1Reference 1Maione F et al. · 2015AnimalMolecular mechanism of tanshinone IIA and cryptotanshinone in platelet anti-aggregating effects: an integrated study of pharmacology and computational analysis — rat platelet and docking studyView study →}.

A 2025 network-pharmacology and metabolomics paper revisits the mechanism without adding a functional assay ^{2Reference 2Huang J et al. · 2025In vitroIntegrating network pharmacology and metabolomics to elucidate the mechanism of cryptotanshinone against platelet aggregation — computational and in vitro studyView study →}.

Dan shen’s antiplatelet reputation belongs mainly to the salvianolic acids, not to this molecule.

The pharmacokinetic half of the danshen–warfarin interaction does trace to the tanshinones: in rat liver microsomes the ethyl acetate (tanshinone) extract and the individual tanshinones, tanshinone I, tanshinone IIA and cryptotanshinone, all inhibited warfarin 4′-, 6- and 7-hydroxylation via CYP1A1/2C6/2C11, while the aqueous extract had no effect at all; in vivo, danshen raised steady-state plasma warfarin by 23% ^{3Reference 3Wu WW · 2010In vitroInhibition of warfarin hydroxylation by major tanshinones of danshen (Salvia miltiorrhiza) in the rat in vitro and in vivo — rat in vitro and in vivo studyView study →}.

One of the few helenalin findings on human cells.

In venous blood from healthy volunteers off anti-inflammatories for two weeks, isolated helenalin and 11α,13-dihydrohelenalin inhibited collagen-induced platelet aggregation, thromboxane formation and 5-hydroxytryptamine secretion concentration-dependently at 3–300 µM, helenalin being the more potent, and the authors attributed the effect to thiol-dependent pathways ^{11Reference 11Schröder H et al. · 1990Clinical trialHelenalin and 11 alpha,13-dihydrohelenalin, two constituents from Arnica montana L., inhibit human platelet function via thiol-dependent pathways — in vitro, human volunteers’ plateletsView study →}, the same electrophilic chemistry aimed at a different protein set.

The limit is exposure: 3–300 µM is far above anything topical application could plausibly produce systemically, there are no bleeding-outcome data, and no evidence exists that topical arnica affects platelet function in a person ^{11,12Reference 11Schröder H et al. · 1990Clinical trialHelenalin and 11 alpha,13-dihydrohelenalin, two constituents from Arnica montana L., inhibit human platelet function via thiol-dependent pathways — in vitro, human volunteers’ plateletsView study →Reference 12Committee on Herbal Medicinal Products ( · 2014ReviewAssessment report on Arnica montana L., flos (EMA/HMPC/198794/2012) — regulatory monograph. https://www.ema.europa.eu/en/documents/herbal-report/final-assessment-report-arnica-montana-l-flos_en.pdfView study →}.

In an aporphinoid structure-activity screen it showed strong inhibition of platelet aggregation induced by arachidonic acid, collagen and PAF, but was not listed among the strong inhibitors of ADP-induced aggregation, nor among the vasorelaxants in rat aorta, a list that did include the N-desmethyl relative laurotetanine ^{13Reference 13Chen KS et al. · 1996Antiplatelet and vasorelaxing actions of some aporphinoidsView study →}.

The screen gives no IC50 values, and a separate bioactivity-guided study of Annona purpurea leaves that isolated this alkaloid did not list it among the compounds with significant antiplatelet activity ^{14Reference 14Chang FR et al. · 1998Two new 7-dehydroaporphine alkaloids and antiplatelet action aporphines from the leaves of Annona purpureaView study →}.

The two isolate studies contradict each other, and there are no in-vivo bleeding or thrombosis data.