Alliin (Cysteine Sulfoxide · Garlic Allicin Precursor · Quality Marker)
| Compound | Alliin (S-Allyl-L-cysteine sulfoxide) |
| Chemical class | Organosulfur — Cysteine Sulfoxide (S-Allyl-L-cysteine sulfoxide) |
| CAS | 556-27-4 |
| Primary source | Allium sativum (garlic bulb) — primary storage form of the allicin precursor system |
| Key applications | Allicin precursor, mild cardiovascular, antioxidant, marker for garlic extract quality |
| Claim strength | Moderate |
| Typical form | Garlic extract standardised to alliin content (primary commercial garlic quality marker) |
| Buy from Herbuno |
Name origin: From Allium (garlic genus). Alliin is the S-allyl cysteine sulfoxide — a naturally occurring amino acid derivative and the stable storage form of the allicin precursor system in intact garlic. In the presence of alliinase enzyme (released upon cell disruption), alliin is converted to allicin, pyruvate, and ammonia in a rapid enzymatic reaction. Traditional use: Alliin itself is not individually identified in traditional medicine — it is the stable form of the garlic bioactive system, with its pharmacological significance understood only after its discovery and characterisation in the 1940s–1950s by Arthur Stoll and Ewald Seebeck (who first isolated alliin and characterised the alliin-alliinase → allicin pathway). All traditional garlic therapeutic uses involve alliin as the stored precursor converted to allicin and other organosulfur compounds upon preparation. Research trajectory: Alliin is the primary analytical marker used to standardise commercial garlic extract preparations for allicin yield. Alliin has mild direct biological activity (antioxidant, mild cardiovascular) but its primary pharmacological significance is as the allicin precursor. The AOAC allicin yield method (measuring alliin conversion to allicin) is the industry-standard quality measure for garlic extracts. Commercial source: Garlic Extract Powder and Dehydrated Garlic Powder from Herbuno contain alliin as the primary organosulfur constituent. See sourcing options below.
Evidence for Alliin Applications
Allicin precursor — primary pharmacological role: Alliin is converted to allicin by alliinase within seconds of cell disruption. The allicin generated is responsible for the antimicrobial, cardiovascular, antiplatelet, and most other well-documented garlic pharmacological effects. Alliin’s own biological activity, separate from allicin generation, is mild relative to its conversion product. Claim strength: Moderate (indirect via allicin).
Direct antioxidant activity: Alliin itself has documented radical-scavenging activity and reduces lipid peroxidation in cell models, independent of allicin conversion. The sulfoxide functional group contributes to antioxidant activity. Claim strength: Moderate.
Mild antimicrobial: Alliin at high concentrations has direct antimicrobial activity, separate from allicin generation — though significantly weaker than allicin. The cysteine sulfoxide class of organosulfur compounds has inherent mild antimicrobial properties. Claim strength: Moderate.
Quality specification marker: The alliin content of a garlic extract, determined by HPLC, is the primary commercial quality marker that allows calculation of maximum possible allicin yield (allicin yield = alliin content × 0.818 when complete conversion is assumed). This makes alliin specification the most important analytical parameter for formulating garlic supplement products with meaningful allicin yield claims. Claim strength: High (as an analytical quality marker).
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Dosage & Formulator Specification
Garlic extract is typically standardised to alliin content by HPLC (typically 0.5–2% alliin in dried extract). Allicin yield is calculated from alliin: yield (mg allicin) = alliin content (mg) × 0.818. The Ried meta-analysis used preparations providing 1,800–7,200 µg allicin yield/day — achievable from 2.2–8.8 mg alliin/day — typically requiring 200–800 mg garlic extract (0.5–2% alliin). For maximum allicin delivery: (1) specify alliinase-active extract (not deactivated by heat); (2) use enteric-coated tablets to deliver alliin to the alkaline small intestine where alliinase operates optimally; (3) avoid acidic co-formulation that degrades allicin post-conversion. Specify both alliin content (by HPLC) and allicin yield (by AOAC method) on CoA.
Frequently Asked Questions — Alliin
Why is alliin the preferred analytical marker for garlic extracts over allicin?
Allicin is chemically unstable — it degrades rapidly upon extraction, processing, and storage. Measuring allicin content directly in a garlic extract gives a point-in-time reading that will have decreased by the time the product is consumed. Alliin is stable and can be accurately quantified by HPLC with excellent reproducibility. The allicin yield calculated from alliin represents the maximum allicin the preparation can theoretically generate — a more pharmacologically meaningful and analytically consistent specification than direct allicin measurement in the unstable finished product.
Does dehydrated garlic powder contain alliin?
Yes — if properly dehydrated (spray-dried or freeze-dried at low temperature to preserve alliinase activity), dehydrated garlic powder contains alliin in the same compartmental arrangement as fresh garlic. Adding water to dehydrated garlic powder triggers alliinase activity and allicin generation. For high-allicin preparations, specify low-temperature dehydration (<50°C) to preserve alliinase activity. High-temperature dehydration (above 60°C) inactivates alliinase, leaving alliin without the enzyme needed for conversion — such preparations are alliin-rich but cannot generate allicin without added exogenous alliinase.
Is alliin related to S-allylcysteine (SAC)?
Yes — alliin (S-allyl-L-cysteine sulfoxide) and SAC (S-allyl-L-cysteine) differ only in the sulfoxide group: alliin has an additional oxygen on the sulfur (sulfoxide). Both are S-allyl cysteine derivatives and both occur in garlic, but in different contexts: alliin is the primary fresh garlic organosulfur compound converted to allicin; SAC is the primary aged garlic extract (AGE) organosulfur compound accumulated during the aging process (where alliin and allicin are converted to SAC and SAMC under prolonged aqueous conditions). SAC has different pharmacological properties from alliin and allicin.
What is the alliin content of typical fresh garlic?
Fresh garlic contains approximately 6–14 mg alliin per gram dry weight (0.6–1.4% by dry weight), varying by cultivar, growing conditions, and storage duration. One medium garlic clove (approximately 3 g fresh, 0.9 g dry weight) provides approximately 5–12 mg alliin, capable of generating approximately 4–10 mg allicin upon crushing. This translates to approximately 1,200–3,000 µg allicin yield per clove — within the range studied in clinical blood pressure trials.
Related compounds: Allicin, S-Allylcysteine, Glucoraphanin, Sinigrin
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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