S-Allylcysteine

S-Allylcysteine at a Glance

S-allylcysteine (SAC) is the stable, odourless, water-soluble organosulfur compound that accumulates as garlic is aged, and the standardisation marker for aged garlic extract.

It is the opposite of allicin in every practical respect. Allicin and the reactive garlic sulfides are pungent, unstable and formed only when a clove is crushed; SAC is stable, well absorbed and odourless, which is why aged garlic extract can be standardised to it while raw-garlic products cannot be standardised to allicin.

That makes it the most measurable and reproducible of garlic’s actives.

What It's Used For

S-allylcysteine (SAC) is the odorless, water-soluble organosulfur compound that accumulates as garlic is aged, and it is the standardization marker for aged garlic extract (AGE). Its defining feature separates it from the rest of garlic’s chemistry: unlike allicin, ajoene and the diallyl sulfides — which are reactive, unstable and poorly bioavailable — SAC is chemically stable and highly bioavailable ^{4,1Reference 4Kodera Y et al. · 2002Physical, chemical and biological properties of S-allylcysteine, an amino acid derived from garlicView study →Reference 1Nagae S et al. · 1994Pharmacokinetics of the garlic compound S-allylcysteineView study →}.

(It is also distinct from alliin, its oxidized sulfoxide precursor.) That stability makes it both a good research molecule and the reason AGE is standardized to it. Its most-developed pharmacology is preclinical antioxidant and neuroprotective activity via the Nrf2/ARE antioxidant program ^{5,7Reference 5Colín-González AL et al. · 2015On the antioxidant, neuroprotective and anti-inflammatory properties of S-allylcysteine: an updateView study →Reference 7Shi H et al. · 2015In vitroS-allylcysteine activates the Nrf2-dependent antioxidant response and protects neurons against ischemic injury in vitro and in vivoView study →}.

The key honesty point runs through the whole page: the human cardiovascular evidence is for aged garlic extract standardized to SAC, not for isolated SAC — SAC is the measuring stick, not proven to be the active agent.

A stable, well-absorbed organosulfur— a genuine point of difference from allicin: ~64–98% oral bioavailability across species, renally excreted ^{1,2Reference 1Nagae S et al. · 1994Pharmacokinetics of the garlic compound S-allylcysteineView study →Reference 2Amano H et al. · 2015AnimalMetabolism, excretion and pharmacokinetics of S-allyl-L-cysteine in rats and dogsView study →}, which is exactly why AGE is standardized to it.

Strong preclinical antioxidant/neuroprotection:Nrf2/ARE activation raising SOD/catalase/glutathione and preserving BDNF across brain-injury models ^{5,7,8Reference 5Colín-González AL et al. · 2015On the antioxidant, neuroprotective and anti-inflammatory properties of S-allylcysteine: an updateView study →Reference 7Shi H et al. · 2015In vitroS-allylcysteine activates the Nrf2-dependent antioxidant response and protects neurons against ischemic injury in vitro and in vivoView study →Reference 8Reyes-Soto CY et al. · 2020S-allylcysteine protects against excitotoxic damage via Nrf2/ARE binding and BDNF preservationView study →} — but no human neuro trials.

The honest headline:the human blood-pressure and cholesterol benefits belong to aged garlic extract (a whole preparation with dozens of co-compounds), not to SAC in isolation ^{16,17Reference 16Ried K et al. · 2016Garlic lowers blood pressure in hypertensive individuals, regulates serum cholesterol and stimulates immunityView study →Reference 17Saadh MJ et al. · 2024Meta-analysisEffects of aged garlic extract on blood pressure in hypertensive patients: a systematic review and meta-analysisView study →}.

Evidence by IndicationStrength of support · Beta

Support is an experimental score — weighted by study type (human > animal > in vitro) and volume. A beta, not a validated metric. Isolated-SAC efficacy is preclinical and the human data are whole-extract, so isolate scores stay low by design. Each application links to its write-up.

Mechanisms

Target / pathway	Effect	Relevant to
Nrf2/ARE → ↑ SOD, catalase, GSH-Px, HO-1	endogenous antioxidant-enzyme induction	neuroprotectionhepatoprotection
Direct radical/ROS scavenging	↓ lipid peroxidation, mitochondrial protection	excitotoxic and metabolic-stress models
NF-κB modulation	↓ inflammatory signaling; pro-apoptotic in tumor cells	anti-inflammatoryanticancer
AMPK activation	↓ hepatic lipogenesis	metabolic/hepatic
H₂S / NO modulation, endothelial function (AGE context)	vasorelaxation, blood-pressure effect	cardiovascular

Pharmacokinetics

This is SAC’s strongest point of difference from every reactive garlic sulfur compound. It is well absorbed and stable: oral bioavailability is ~64% in mouse, ~89% in rat and ~98% in dog ^{1Reference 1Nagae S et al. · 1994Pharmacokinetics of the garlic compound S-allylcysteineView study →}, with a modern rat/dog study confirming rapid, near-complete absorption ^{2Reference 2Amano H et al. · 2015AnimalMetabolism, excretion and pharmacokinetics of S-allyl-L-cysteine in rats and dogsView study →}. It is odorless, water-soluble and not degraded like allicin, so it is measurable in plasma and tissue — which is precisely why AGE is standardized to it ^{4,3Reference 4Kodera Y et al. · 2002Physical, chemical and biological properties of S-allylcysteine, an amino acid derived from garlicView study →Reference 3Nakamoto M et al. · 2025ReviewPharmacokinetics of sulfur-containing compounds in aged garlic extract (review)View study →}. It distributes to plasma, liver and kidney, is partly N-acetylated, and is excreted primarily in the urine as SAC and its N-acetyl metabolite ^{2,1Reference 2Amano H et al. · 2015AnimalMetabolism, excretion and pharmacokinetics of S-allyl-L-cysteine in rats and dogsView study →Reference 1Nagae S et al. · 1994Pharmacokinetics of the garlic compound S-allylcysteineView study →}. In short, unlike most plant molecules, SAC’s pharmacokinetics are favorable — the caveat is not absorption but that the human efficacy data still come from the whole extract.

Clinical trials

There are no controlled human trials of isolated SAC. All human data are for aged garlic extract standardized to SAC: reviews and meta-analyses of AGE for blood pressure and cholesterol ^{16,17Reference 16Ried K et al. · 2016Garlic lowers blood pressure in hypertensive individuals, regulates serum cholesterol and stimulates immunityView study →Reference 17Saadh MJ et al. · 2024Meta-analysisEffects of aged garlic extract on blood pressure in hypertensive patients: a systematic review and meta-analysisView study →}, an endothelial-function RCT in coronary-artery-disease men ^{18Reference 18Williams MJ et al. · 2005Aged garlic extract improves endothelial function in men with coronary artery diseaseView study →}, and a subclinical-atherosclerosis RCT (AGE plus B-vitamins/folate/L-arginine) ^{19Reference 19Budoff MJ et al. · 2009RCTAged garlic extract supplemented with B-vitamins, folic acid and L-arginine retards the progression of subclinical atherosclerosis: a randomised clinical trialView study →}; a separate RCT of fermented garlic extract reduced GGT ^{20Reference 20Kim HN et al. · 2017RCTEfficacy and safety of fermented garlic extract on hepatic function: a double-blind, randomised, placebo-controlled trialView study →}. Every clinical claim must be attributed to the extract, with SAC named only as the marker.

Completed	Planned	Terminated	Preclinical
—(isolate); AGE RCTs/meta-analyses	—	—	Extensive

Last checked: July 2026.

Toxicity & Safety

SAC has very low toxicity — a genuinely safe compound, markedly less toxic than allicin and its reactive congeners, with a high margin of safety in rodent work (roughly an order of magnitude less toxic than allicin or diallyl disulfide) ^{4,21Reference 4Kodera Y et al. · 2002Physical, chemical and biological properties of S-allylcysteine, an amino acid derived from garlicView study →Reference 21Mikaili P et al. · 2013Therapeutic uses and pharmacological properties of garlic, shallot and their biologically active compoundsView study →}. Its interaction profile is milder than fresh garlic’s, too: the antiplatelet/anticoagulant caution attached to garlic comes chiefly from allicin, ajoene and the diallyl sulfides, and SAC itself is only a weak antiplatelet agent, so the isolate carries less bleeding risk. The standard garlic caution with warfarin, antiplatelets and around surgery still applies when it is taken as AGE (a whole extract) ^{21Reference 21Mikaili P et al. · 2013Therapeutic uses and pharmacological properties of garlic, shallot and their biologically active compoundsView study →}.

Dosage

There is no isolated-SAC human dose, and nothing here is a recommendation. Cardiovascular trials use aged garlic extract at roughly 600–1200 mg AGE/day ^{16Reference 16Ried K et al. · 2016Garlic lowers blood pressure in hypertensive individuals, regulates serum cholesterol and stimulates immunityView study →}; the meta-analysis that reported significant benefit only above ~1200 mg/day has been retracted ^{17Reference 17Saadh MJ et al. · 2024Meta-analysisEffects of aged garlic extract on blood pressure in hypertensive patients: a systematic review and meta-analysisView study →}, so no threshold within that range is established. AGE products are standardized to a stated SAC content rather than dosed as free SAC, so these regimens deliver only milligram quantities of SAC embedded in a whole extract.

References

Nagae S, et al. (1994). Pharmacokinetics of the garlic compound S-allylcysteine. Planta Medica. https://pubmed.ncbi.nlm.nih.gov/8073085/
Amano H, et al. (2015). Metabolism, excretion and pharmacokinetics of S-allyl-L-cysteine in rats and dogs. Drug Metabolism and Disposition. https://pubmed.ncbi.nlm.nih.gov/25681129/
Nakamoto M, Kunimura K, Ohtani M (2025). Pharmacokinetics of sulfur-containing compounds in aged garlic extract (review). Experimental and Therapeutic Medicine. https://pubmed.ncbi.nlm.nih.gov/40171136/
Kodera Y, Suzuki A, Imada O, et al. (2002). Physical, chemical and biological properties of S-allylcysteine, an amino acid derived from garlic. Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/11804540/
Colín-González AL, Ali SF, Túnez I, et al. (2015). On the antioxidant, neuroprotective and anti-inflammatory properties of S-allylcysteine: an update. Neurochemistry International. https://pubmed.ncbi.nlm.nih.gov/26122973/
Colín-González AL, Santana RA, Silva-Islas CA, et al. (2012). The antioxidant mechanisms underlying the aged-garlic-extract- and S-allylcysteine-induced protection. Oxidative Medicine and Cellular Longevity. https://pubmed.ncbi.nlm.nih.gov/22685624/
Shi H, Jing X, Wei X, et al. (2015). S-allylcysteine activates the Nrf2-dependent antioxidant response and protects neurons against ischemic injury in vitro and in vivo. Journal of Neurochemistry. https://pubmed.ncbi.nlm.nih.gov/25393425/
Reyes-Soto CY, Rangel-López E, Galván-Arzate S, et al. (2020). S-allylcysteine protects against excitotoxic damage via Nrf2/ARE binding and BDNF preservation. Neurotoxicity Research. https://pubmed.ncbi.nlm.nih.gov/32813208/
Pérez-De La Cruz V, González-Cortés C, Pedraza-Chaverrí J, et al. (2006). Protective effect of S-allylcysteine on 3-nitropropionic-acid-induced lipid peroxidation and mitochondrial dysfunction in rat brain synaptosomes. Brain Research Bulletin. https://pubmed.ncbi.nlm.nih.gov/16377446/
Shinkawa H, Takemura S, Minamiyama Y, et al. (2009). S-allylcysteine is effective as a chemopreventive agent against porcine-serum-induced hepatic fibrosis in rats. Osaka City Medical Journal. https://pubmed.ncbi.nlm.nih.gov/20088405/
Basu C, Sur R (2018). S-allylcysteine alleviates hydrogen-peroxide-induced oxidative injury and apoptosis through Akt/Nrf-2/HO-1 in HepG2 cells. BioMed Research International. https://pubmed.ncbi.nlm.nih.gov/30515391/
Hwang YP, Kim HG, Choi JH, et al. (2013). S-allylcysteine attenuates free-fatty-acid-induced lipogenesis in human HepG2 cells through an AMPK-dependent pathway. Journal of Nutritional Biochemistry. https://pubmed.ncbi.nlm.nih.gov/23465592/
Agbana YL, Ni Y, Zhou M, et al. (2020). Garlic-derived bioactive compound S-allylcysteine inhibits cancer progression through diverse molecular mechanisms. Nutrition Research. https://pubmed.ncbi.nlm.nih.gov/31835095/
Orozco-Morales M, Hernández-Pedro NY, Barrios-Bernal P, et al. (2021). S-allylcysteine induces cytotoxic effects in two human lung cancer cell lines via downregulation of Nrf2 and NF-κB and apoptosis. Anti-Cancer Drugs. https://pubmed.ncbi.nlm.nih.gov/33136700/
Pai MH, Kuo YH, Chiang EP, et al. (2012). S-allylcysteine inhibits tumour progression and the epithelial-mesenchymal transition in a mouse xenograft model of oral cancer. British Journal of Nutrition. https://pubmed.ncbi.nlm.nih.gov/22011514/
Ried K, et al. (2016). Garlic lowers blood pressure in hypertensive individuals, regulates serum cholesterol and stimulates immunity. The Journal of Nutrition. https://pubmed.ncbi.nlm.nih.gov/26764326/
Saadh MJ, et al. (2024). Effects of aged garlic extract on blood pressure in hypertensive patients: a systematic review and meta-analysis. Prostaglandins & Other Lipid Mediators. https://pubmed.ncbi.nlm.nih.gov/39437887/ ⚠ RETRACTED — retraction notice: Prostaglandins Other Lipid Mediat. 2026, https://pubmed.ncbi.nlm.nih.gov/42527229/
Williams MJ, Sutherland WH, McCormick MP, et al. (2005). Aged garlic extract improves endothelial function in men with coronary artery disease. Phytotherapy Research. https://pubmed.ncbi.nlm.nih.gov/16041725/
Budoff MJ, Ahmadi N, Gul KM, et al. (2009). Aged garlic extract supplemented with B-vitamins, folic acid and L-arginine retards the progression of subclinical atherosclerosis: a randomised clinical trial. Preventive Medicine. https://pubmed.ncbi.nlm.nih.gov/19573556/
Kim HN, Kang SG, Roh YK, et al. (2017). Efficacy and safety of fermented garlic extract on hepatic function: a double-blind, randomised, placebo-controlled trial. European Journal of Nutrition. https://pubmed.ncbi.nlm.nih.gov/27743130/
Mikaili P, Maadirad S, Moloudizargari M, et al. (2013). Therapeutic uses and pharmacological properties of garlic, shallot and their biologically active compounds. Iranian Journal of Basic Medical Sciences. https://pubmed.ncbi.nlm.nih.gov/24379960/