L-leucine
L-leucine is an essential, branched-chain amino acid. Most commercial L-leucine is made by bacterial fermentation of glucose or sucrose, then purified and crystallized; some is still made by hydrolyzing keratin from feathers or hair, so buyers who need vegan material ask for the source. It is a bitter, poorly wetting white powder, so brands often buy instantized grades for drink mixes and standard crystalline grades for capsules and tablets.
Suppliers sell different products under the same name. Specify the one you need.
Standard fine crystalline powder for capsules, tablets and dry blends.
L-leucine agglomerated or coated with a small amount of lecithin (often sunflower or soy) so it wets and disperses in water; check the lecithin source for allergen labeling.
L-leucine made by bacterial fermentation of corn, cassava or beet sugar; the source and any vegan statement appear on the supplier's spec.
L-leucine tested to the USP monograph, used where a compendial grade is required for supplements.
Compare each result with your own specification when the lot arrives.
Store L-leucine in tightly closed, lined containers in a cool, dry place away from light and strong odors, and reseal opened packs promptly. Shelf life or retest date is set by the supplier's specification; assay, loss on drying and micro are the usual retest points for older stock.
Record assay, source (fermentation or keratin) and, for instantized grades, the lecithin type and level for each lot. Rotate stock FEFO and check that instantized lots still disperse before using older material.
Facts from regulators and standards bodies, each linked to its source.
21 CFR 172.320 lists L-leucine among the amino acids that may be safely used as nutrients added to foods.
Source: ecfr.gov (opens in a new tab)Under 21 CFR 172.320, added plus naturally present L-leucine may not exceed 8.8 percent by weight of the total protein of the finished food.
Source: ecfr.gov (opens in a new tab)GRN 308 (L-leucine, notified by Ajinomoto Aminoscience) closed on April 30, 2010 with FDA having no questions, for meal replacements, sports and isotonic beverages, vitamin-fortified waters and meal replacement bars.
Source: hfpappexternal.fda.gov (opens in a new tab)GRN 523 (L-leucine, notified by INNOBIO) closed on December 11, 2014 with FDA having no questions, for similar beverage and bar uses.
Source: hfpappexternal.fda.gov (opens in a new tab)This is general information, not regulatory advice. Status differs by country and by how the ingredient is used, so check the rules for your product and market.
Manufacturers and distributors whose own websites say they sell it.
Manufacturer · Raleigh, NC
North American subsidiary of the Ajinomoto Group. It supplies pharmaceutical- and food-grade amino acids made by fermentation, in pack sizes from R&D pails to bulk, plus custom amino acid blends.
Suppliers are in alphabetical order and none pays to appear. Each claim is checked against the supplier’s own website on the date shown. Ask for the specification sheet and a recent COA before you order, and confirm details with the supplier.
Common forms include crystalline, instantized, fermented (plant-sugar) grade and uSP grade. Ask each supplier for the specification sheet of the exact grade they quote.
Expect identity, assay, related substances, loss on drying and residue on ignition, heavy metals and microbiology and wettability (instantized grades), each with its method, specification and result for that lot.
Store L-leucine in tightly closed, lined containers in a cool, dry place away from light and strong odors, and reseal opened packs promptly. Shelf life or retest date is set by the supplier's specification; assay, loss on drying and micro are the usual retest points for older stock.
21 CFR 172.320 lists L-leucine among the amino acids that may be safely used as nutrients added to foods. Under 21 CFR 172.320, added plus naturally present L-leucine may not exceed 8.8 percent by weight of the total protein of the finished food. GRN 308 (L-leucine, notified by Ajinomoto Aminoscience) closed on April 30, 2010 with FDA having no questions, for meal replacements, sports and isotonic beverages, vitamin-fortified waters and meal replacement bars. GRN 523 (L-leucine, notified by INNOBIO) closed on December 11, 2014 with FDA having no questions, for similar beverage and bar uses.
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