Garlic
Plant Bioactives offers unusual expertise in the analysis and science of garlic and garlic supplements, unequaled by any other laboratory in the United States. In fact, many of the methods routinely employed for analysis of garlic products were developed by the scientists at Plant Bioactives. Quality analyses of garlic supplements are difficult to achieve because of the instability and unavailability of some of the standards and the difficulty of obtaining or preparing them in pure form. Furthermore, the need to perform high quality tests on garlic supplements has reached a critical point due to the many failed clinical trials with garlic supplements that have recently been published and later found to be the fault of the quality of the tablets. With approximately 25 garlic research publications and more than 20 years of analytical and research experience on garlic and garlic supplements, one can be confident in the quality of the analyses at Plant Bioactives.
Garlic Composition Analyses
For many years Plant Bioactives has offered the following analyses of garlic and garlic supplements:
Garlic bulbs, powders, extracts
- Allicin yield/potential
- Total thiosulfinates yield (allicin, allyl methyl and allyl 1-propenyl thiosulfinates)
- Alliin
- Gamma-glutamylcysteines (S-allyl, S-1-propenyl, S-methyl)
- S-allylcysteine
- Gamma-glutamylcysteines and S-allylcysteine
Garlic oils and components
- Steam-distilled oil, sometimes called "essential oil" (total allyl sulfides)
- Oil-macerate (ajoene, vinyl dithiins, major allyl sulfides)
- Major allyl sulfides (diallyl disulfide, diallyl trisulfide, allyl methyl trisulfide)
- Ajoene and vinyl dithiins
- Ajoene
Garlic Supplement Quality Tests
The failure of most garlic supplement brands to release their label claim for allicin when tested under the gastrointestinal dissolution conditions defined by the USP has revealed a critical need for the quality evaluation of garlic powder supplements to extend beyond simple composition analysis. Recent testing of 24 brands of garlic supplements found that low tablet alliinase activity and slow tablet disintegration were the main causes for product failure. Plant Bioactives now offers the following tests designed to help products meet label claims for allicin release:
- Dissolution Allicin Release, USP-NF (tablets/capsules)
- Disintegration Time (under USP-NF dissolution conditions)
- Alliinase Activity (tablets/capsules)
- Alliinase Activity (powders)
- Limited Alliinase Activity, USP-NF (tablets/capsules)
- Potential Allicin, USP-NF (tablets/capsules)
- Allicin Bioavailability
Dissolution Allicin Release, USP-NF (tablets/capsules)
The USP-National Formulary will soon require supplements making allicin label claims to be able to release 75-80% of the label claim under defined gastrointestinal dissolution conditions (Pharmacopeial Forum 2000, 26, pp. 1354-1357; generally described in USP method 724A). Passing the test requires that six out of six tablets release at least 80% of the label claim for allicin after being incubated in acid for 2 hours and in intestinal buffer for 1 hour. If one or more of the six tablets fails to do so, then another six tablets must be tested and the average of all twelve tablets must release at least 75% of label claim with no tablet releasing less than 60% of label claim.
Because a dissolution apparatus can only accommodate 6-8 tablets, only one lot can be tested at one time for meeting the method requirement. As an economical alternative during product development, before doing a final test of six tablets per lot, Plant Bioactives will test 2-4 lots of 2-4 tablets (6-8 total tablets) per lot for only 15-36% more cost than testing a single lot.
Disintegration Time (under USP-NF dissolution conditions)
This test measures the amount of time needed for tablets to disintegrate while conducting the dissolution allicin release assay by extending the buffer incubation time, if needed, from 1 hour until completely disintegrated, with a maximum cut-off time of 4 hours. Half of the brands tested so far have required at least 3 hours to disintegrate, being a major cause for failure to pass the allicin release test.
Alliinase Activity (tablets/capsules)
A second major reason for products to give low dissolution allicin release values is low alliinase activity of the tablets, which is most often caused by certain excipients and other tablet manufacturing conditions. Hence, the alliinase activity of tablets is often much lower than that of the garlic powder from which they are made. A comparison of the alliinase activity of the tablets with that of the employed garlic powder will reveal the presence of alliinase-inhibiting excipients or the use of deleterious tablet making procedures.
The alliinase activity assay measures the actual biochemical activity of the alliinase (initial velocity, linear range) and is reported in activity units as the micrograms of allicin formed per minute per gram of garlic powder in the tablet/capsule. In order for supplements to pass the dissolution allicin release assay, the alliinase activity needs to be at least 4000 units.
Alliinase Activity (powders)
The alliinase activity of garlic powders can range from 200 units for spice quality powders to 15,000 units for the best supplement quality powders. Therefore, it is important to measure the alliinase activity of the garlic powder that will be used to make supplements. Since there is probably always some loss of activity upon tablet preparation, the alliinase activity of the powder should be well above 4000 units. A range of 6000-8000 units should be sufficient, depending upon the amount of alliinase-inhibiting excipients present in the tablets.
Limited Alliinase Activity, USP-NF (tablets/capsules)
The USP-National Formulary will also contain a method for alliinase activity (Pharmacopeial Forum 2000, 26, pp. 1354-1357). The method simply requires that no more than 1% of the original alliin content remain after being activated for 5 minutes. Hence, the method only gives a rough approximation of activity and does not measure the activity in a manner that can be quantified, making it difficult to determine if attempts at improving the activity have had any effect. It is not certain if meeting the USP-NF alliinase activity standard will represent enough activity to pass the dissolution allicin release assay. While Plant Bioactives will perform this test, the Alliinase Activity test will provide better information for being able to improve product quality.
Potential Allicin, USP-NF (tablets/capsules)
More commonly referred to as allicin yield or allicin potential, but designated as potential allicin in the USP Pharmacopeial Forum, potential allicin refers to the maximum amount of allicin that can be produced from pulverized tablets or emptied capsules under optimum (non-gastrointestinal) conditions for stimulating alliinase activity. Potential allicin is used to evaluate dissolution allicin release, which is measured as a percent of the potential allicin.
Allicin Bioavailability
Although the dissolution allicin release test provides a reasonable and economical estimate of what is taking place in the body, the best test of the ability of garlic supplements to produce allicin in the body is a bioavailability test in humans. Plant Bioactives determines allicin bioavailability by measuring the total amount of allyl methyl sulfide, the main body metabolite of allicin, exhaled over a 48-hr period after consuming a product (at a dose of 60 mg of allicin yield) compared to consuming a standard. Minimally, the product is tested two times in one person with a well-established bioavailability response.
