Herb reference
Allium sativum L.
Crystalis is a reference resource for herbal, crystal, and somatic practice.
This library is designed to help readers orient, compare, and research. It is not a substitute for medical care or practitioner judgment.
Botanical / meta
A bulbous perennial plant growing 30–120 cm tall, producing a compact bulb (the "head") composed of 4–20 individual cloves enclosed in a papery white to pinkish tunic. Long, flat, linear leaves emerge from the bulb base, and an umbel of small greenish-white or pink flowers may develop on a leafless stalk.
Garlic's bioactive compounds are primarily organosulfur compounds formed when the bulb's tissues are disrupted. Alliin (S-allyl-L-cysteine sulfoxide) is converted by the enzyme alliinase into allicin, a thiosulfinate responsible for garlic's characteristic odor and many of its pharmacological effects. Other important constituents include ajoene, diallyl disulfide (DADS), diallyl trisulfide (DATS), S-allylcysteine (SAC), and S-allylmercaptocysteine (SAMC). Allicin is highly unstable and degrades rapidly into various organosulfur compounds.
The practical read
Garlic's bioactive compounds are primarily organosulfur compounds formed when the bulb's tissues are disrupted. Alliin (S-allyl-L-cysteine sulfoxide) is converted by the enzyme alliinase into allicin, a thiosulfinate responsible for garlic's characteristic odor and many of its pharmacological effects. Other important constituents include ajoene, diallyl disulfide (DADS), diallyl trisulfide (DATS), S-allylcysteine (SAC), and S-allylmercaptocysteine (SAMC). Allicin is highly unstable and degrades rapidly into various organosulfur compounds.
Route panel
Evidence and safety may differ by preparation. Essential oil, tea, tincture, extract, infused oil, and topical use are not interchangeable.
Quality
Plant individual cloves (pointed end up) in well-drained, fertile soil in autumn for summer harvest. Requires full sun and consistent moisture during growth. Hardneck varieties produce scapes; softneck varieties store longer. Harvest when lower leaves turn brown and dry. Cure bulbs in a warm, shaded, well-ventilated area for 2–4 weeks before storage.
Fresh bulbs should be firm with intact, dry outer skins. The allicin potential is highest in fresh-crushed garlic; dried powder and aged garlic extract (AGE) have different constituent profiles. Aged garlic extract (Kyolic) is odorless and contains S-allylcysteine rather than allicin. Available as fresh bulbs, dried powder, aged extract, oil macerate, and enteric-coated tablets. Store in a cool, dry, dark place; do not refrigerate.
Companion
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The deeper layer
Clinical and compound notes are included as a research layer, not as treatment instructions.
Use caution with bleeding disorders and antiplatelet/anticoagulant medications (aspirin, clopidogrel) due to garlic's mild antiplatelet effects, which may add to surgical bleeding risk; evidence for a direct warfarin interaction specifically is mixed. Discontinue concentrated supplements at least 7–10 days before surgery. May cause gastrointestinal upset, heartburn, and flatulence, especially on an empty stomach. Contraindicated in pregnancy in medicinal doses, though culinary use is considered safe. Topical application can cause chemical burns and contact dermatitis — never apply raw garlic directly to skin. May interact with protease inhibitors and some antidiabetic medications. Rare cases of allergic reactions have been reported.
Questions
Garlic has mild antiplatelet effects from its organosulfur compounds, so caution is warranted with bleeding disorders and with antiplatelet or anticoagulant medications such as aspirin and clopidogrel, where it may add to surgical bleeding risk; evidence for a direct warfarin interaction specifically is mixed. Concentrated garlic supplements should be discontinued at least seven to ten days before surgery. Garlic may also interact with protease inhibitors and with some antidiabetic medications. It commonly causes gastrointestinal upset, heartburn, and flatulence, especially on an empty stomach, and it is contraindicated in medicinal doses during pregnancy, although culinary use is considered safe. Raw garlic should never be applied directly to skin, as it can cause chemical burns and contact dermatitis.
Garlic's key activity depends on allicin, which is not present in the intact bulb but forms when tissue is crushed or chopped and the enzyme alliinase converts alliin into allicin. Crushing or mincing raw garlic and letting it stand for about ten minutes before cooking allows allicin to form and become more heat-stable, since immediate high heat inactivates alliinase and limits allicin production. Allicin itself is highly unstable and degrades quickly into compounds such as ajoene, diallyl disulfide, and diallyl trisulfide, which carry much of garlic's ongoing activity. Aged garlic preparations instead favor stable compounds like S-allylcysteine. Meta-analyses of garlic supplementation have reported modest reductions in blood pressure and serum cholesterol at the doses studied.
Quality fresh garlic bulbs should be firm and heavy with tight, papery skins and no soft spots, sprouting, or mold. A strong pungent aroma when a clove is cut is the practical marker of intact alliin and active alliinase, the enzyme system that generates allicin. For supplements, the meaningful quality measure is allicin-releasing potential or allicin yield, since many products list alliin content but deliver little actual allicin if the alliinase is inactivated by processing. Enteric coating is often used to protect alliinase from stomach acid so allicin can form in the gut. Odorless products that make no allicin claim may deliver little of garlic's characteristic activity.
The forms of garlic differ mainly in which organosulfur compounds dominate. Fresh crushed garlic delivers allicin and its rapid breakdown products such as ajoene and diallyl trisulfide, giving the strongest pungency and the classic odor. Aged garlic extract is processed over time so that unstable allicin gives way to stable, odorless compounds like S-allylcysteine and S-allylmercaptocysteine, which is why aged products are marketed as odorless. Garlic oil and powder fall in between, depending on how they are made and whether alliinase survives processing. Because the active profile shifts with form, fresh, aged, and supplement garlic are not simply interchangeable, and the chosen form should match the intended use.
Whole garlic bulbs store best in a cool, dry, well-ventilated place away from light, where they keep for several weeks to a few months; refrigeration is not ideal as it can encourage sprouting and rubbery texture. Do not store raw garlic in oil at room temperature, since this creates a botulism risk; any garlic-in-oil should be refrigerated and used quickly. Peeled or chopped garlic should be refrigerated and used within a few days, as its allicin-derived compounds degrade and the flavor fades. Garlic supplements should be kept sealed, cool, and dry and used within their labeled shelf life to preserve allicin-releasing potential. Soft, sprouting, or moldy bulbs should be discarded.
Sources & Citations
Peer-reviewed sources for the pharmacological and clinical claims on this page. Crystalis herb entries describe tradition and current research; they are reference, not medical advice.
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Resource framing
Crystalis is a reference resource for herbal, crystal, and somatic practice.
This library is designed to help readers orient, compare, and research. It is not a substitute for medical care or practitioner judgment.
Clinical and compound notes are included as a research layer, not as treatment instructions.
Evidence and safety may differ by preparation. Essential oil, tea, tincture, extract, infused oil, and topical use are not interchangeable.