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Obstetrics & Gynecology 2006;107:1337-1343
© 2006 by The American College of Obstetricians and Gynecologists
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ORIGINAL RESEARCH

Variation in Concentration and Labeling of Ginger Root Dietary Supplements

Harvey A. Schwertner, PhD1, Deborah C. Rios2 and Joshua E. Pascoe3

From 1Clinical Research, Wilford Hall Medical Center, Lackland AFB, Texas; 2Department of Science, Castle Hills First Baptist School, San Antonio, Texas; and 3Department of Chemistry, United States Air Force Academy, Colorado.


   ABSTRACT
TOP
ABSTRACT
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
OBJECTIVE: Ginger root dietary supplements are often used to alleviate symptoms of nausea and vomiting associated with pregnancy. In this study, we determined the variation in 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol concentrations and labeling of different brands of ginger root dietary supplements.

METHODS: Ten different ginger root dietary supplements were purchased randomly at local pharmacies and health food stores. The 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol concentrations of the dietary supplements were determined by high-performance liquid-chromatography. In addition, we examined the container labeling for the amount of ginger root powder or extract in each capsule, the serving size, ingredients, expiration date, lot number, standardization procedure, and suggested use.

RESULTS: The 6-gingerol concentration of the ginger powder dietary supplements ranged from 0.0 to 9.43 mg/g, (mean ± standard deviation, 2.56 ± 2.95 mg/g), 6-shogaol ranged from 0.16 to 2.18 mg/g (1.27 ± 0.58), 8-gingerol ranged from 0.00 to 1.1 mg/g (0.47 ± 0.34), and 10-gingerol ranged from 0.00 to 1.40 mg/g (0.36 ± 0.51). The amounts of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol in the ginger root dietary supplements varied widely on both a milligram per gram basis and on a milligram per capsule basis. Likewise, the suggested ginger serving sizes varied from 250 mg to 4.77 g per day.

CONCLUSION: The results of this study indicate that there is a wide variation in the gingerol composition and in the suggested serving sizes of ginger root powder from different manufacturers.

LEVEL OF EVIDENCE: II-3

Ginger (Zingiber officinale Roscoe) is widely used as a dietary supplement as well as a spice and flavoring agent in foods and beverages. Ginger has been used to treat a variety of medical conditions, including nausea and motion sickness. Ginger dietary supplements have recently been shown to be effective in relieving the symptoms of nausea and vomiting associated with pregnancy. A recent comprehensive review of 6 double-blind, randomized controlled trials has shown that ginger may be effective in treating pregnancy-related nausea and vomiting.7 Four of the clinical trials showed ginger to be more effective in relieving nausea than the placebo, and two showed that ginger was as effective as the vitamin B6 reference drug. There were no significant adverse effects on pregnancy outcomes in any of the 6 clinical trials.

The results with ginger have not always been consistent, even in studies involving pregnancy-related nausea. Meta-analysis, for example, failed to show that ginger is effective in the treating postoperative nausea, motion sickness, or nausea of other etiology.8 The factors contributing to the variability in response to ginger in the clinical studies are not known. Such differences, however, could be due to differences in the doses administered, the duration of the treatment, the quality of the ginger products used, or to differences in the composition of the ginger powders and ginger extracts used in the studies. The composition of the ginger constituents have not been analyzed in any of the clinical studies. Standardization of the ginger composition and doses used in clinical studies is needed if the clinical studies are to be reproduced and if the efficacies of ginger and its components are to be established.

6-Gingerol, 8-gingerol, and 10-gingerol have been identified as the principal pungent components of ginger powder. 6-Gingerol and the other pungent compounds present in ginger powder have been shown to have analgesic, antipyretic, and cardiotonic effects12 and to inhibit spontaneous motor activities and prostaglandin biosynthesis.13 In addition, 6-gingerol has been shown to have antioxidant and anti-inflammatory properties,13,14 to suppress cytokine formation,14,15 and to promote angiogenesis.15 6-Shogaol, a dehydration product of 6-gingerol, is also found in ginger powder, but not in fresh ginger powder.10 6-Shogaol appears to be formed from 6-gingerol during thermal processing or long-term storage and has no known pharmacological properties.10,11 The purpose of this study was to determine the variability in the 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol concentrations, the recommended serving sizes, and the labeling of 10 different brands of ginger root dietary supplements.


   MATERIALS AND METHODS
TOP
ABSTRACT
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
6-Gingerol, 6-shogaol, 8-gingerol, and 10-gingerol were obtained from ChromaDex Inc (Santa Ana, CA). 6-Gingerol was also obtained from Aldrich Chemical Company (Milwaukee, WI) and Wako Pure Chemical (Osaka, Japan). USP Reference Standard Powdered Ginger (Cat. No. 29150-4) was obtained from U.S. Pharmacopeia (USP, Rockville, MD). High-performance liquid chromatography (HPLC)-grade methanol and ethyl acetate were obtained from Fisher Scientific (Fair Lawn, NJ). Ten different ginger root dietary supplements were obtained from health food stores and pharmacies in San Antonio, Texas. The Wilford Hall Medical Center Institutional Review Board approved the study protocol.

Ten capsules containing ginger powder were opened, placed in a beaker, and mixed to insure that a homogenous sample was obtained. Two hundred fifty milligrams of each sample were weighed out in duplicate and placed in separate 16 x 125 mm round-bottom glass centrifuge tubes. Ten milliliters of ethyl acetate were then added with a repipet to each of the tubes. The tubes were capped, mixed briefly, and allowed to sit overnight at room temperature. The ginger samples were extracted on an Eberbach shaker at slow speed for about 30 minutes. The samples were centrifuged at 2,500 ± 100 rpm (rotor 216, IEC CentraGP8R, Needham Heights, MA) for 20 minutes at 25 ± 4°C. The top organic layer was transferred with a Pasteur pipet to separate 16 x 125 mm glass conical centrifuge tubes, and the extracts were evaporated under nitrogen at 45 ± 2°C in a Zymark Turbovap (Caliper Life Sciences, Hopkinton, MA). The ginger dietary supplements were then re-extracted with 10.0 mL of ethyl acetate, and the extracts were transferred to the tubes containing the first extract. After evaporating the ethyl acetate, each extract was reconstituted in 2.0 mL of the mobile phase (methanol-water 65:35, vol/vol). The extracts were vortex mixed for about 25 seconds and centrifuged at 2,000 ± 50 rpm for 20 minutes to further remove any particulate material. The extracts were then transferred with a Pasteur pipet to 70-µL injection vials and capped.

6-Gingerol, 6-shogaol, 8-gingerol, and 10-gingerol used for preparing the standards were dried over silica gel for at least 3 hours under vacuum and then weighed. Approximately 10.0 mg of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol were weighed and transferred to separate 16 x 125 mm screw-capped glass centrifuge tubes. Sufficient HPLC-grade methanol was added to each standard to produce a stock standard of 1.0 mg/mL. Standards containing 500.0 µg/mL of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol were prepared by transferring 5.0 mL (5,000 µg) of each of the stock standards to a 16 x 125 mm conical centrifuge tube, evaporating the methanol at 45 ± 2°C, and reconstituting in 10.0 mL of methanol-water (65:35, vol/vol). Serial dilutions of the 500.0 µg/mL standard were made to produce the 250.0, 100.0, 50.0, 25.0, and 10.0 µg/mL working standards. All ginger standards were capped and stored at 4 ± 4°C until used.

The ginger extracts were analyzed on a HPLC system consisting of a Waters 600E Controller, 717 Autosampler, 996 Photodiode Array Detector (PDA), and a Millennium 2010 Chromatography Manager (Waters, Milford, MA). Chromatographic analysis was performed on a 3.9 x 150 mm Waters Symmetry C-8 reversed-phase column (Cat. No. WATO 54235) with methanol-water (65:35, vol/vol) as the mobile phase. The HPLC operating parameters were as follows: injection volume 25 µL, column flow rate 1.0 mL/minute, chromatographic run time 48.0 minutes, and PDA spectra recording 282 nm.


   RESULTS
TOP
ABSTRACT
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
The ginger dietary supplements that were analyzed are listed in Table 1. Information is provided on the brand name, manufacturer, formulation, serving size, lot number, expiration date, ingredients present, the standardization procedures used, and the intended use. Most of the supplements were formulated in gelatin capsules. Seven of the 8 ginger root powder dietary supplements stated that the capsules contained either 530 or 550 mg of ginger root powder per capsule, one contained 250 mg of ginger root powder, one was obtained in bulk form from a self-serve herbs bin (Sun Harvest Farms), and one contained a ginger root extract (Enzymatic Therapy) (Table 1).


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  		Table 1. Name of Dietary Supplement, Formulation, Serving Size, Manufacturer, Lot Number, Expiration Date, Other Ingredients, Standardization, and Suggested Use

 

The serving sizes of the ginger dietary supplements varied widely from brand to brand (Table 1). The serving size of 4 brands was 1.1 g per serving. The other serving sizes ranged from a low of 250 mg (Nature's Plus Ginger, 1 capsule/day) to a high of 4.77 g per day (Nature's Herbs Ginger Root Herbal Supplement, 1.59 g 3 times per day). Only 5 manufacturers made recommendations as to the number of capsules that should be taken per day. Nature's Plus recommended 1 capsule per day (0.25 g), Nature's Way recommended 8 capsules per day (4.4 g), Nature's Herbs recommended 9 capsules per day (4.77 g), Rexall recommended 2 capsules per day (1.1 g), and Enzymatic Therapy recommended 3 capsules per day (0.3 g extract).

Lot numbers were listed on all of the container labels, expiration dates on 7 of 10 brands, and ingredients on 8 of 10 brands. Only 3 of the brands presented information on how they standardized the composition of their products. Nature's Plus Ginger Standardized Botanical Supplement was standardized to contain 10 mg of volatile oils, Nature's Way to contain 1.3% essential oils, and Enzymatic Therapy Gingerall to contain 20.0 mg of 6-gingerol and 6-shogaol. The bulk ginger powder that was obtained from Sun Harvest did not provide any information on dose, lot number, ingredients, expiration date, standardization, or suggested use. It did state that the ginger powder did not contain sulfites.

In this study, we developed a new extraction procedure and a HPLC procedure for the quantitative analysis of 6-, 8-, and 10-gingerol and 6-shogaol in ginger dietary supplements and in other products containing ginger. The recoveries for 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol from ginger powder with a single ethyl acetate extraction were 94.7, 93.6, 94.9, and 97.1%, respectively; with 2 extractions, the recoveries were 99%. The standard curves for 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol were linear from 10.0 to 1,000.0 µg/mL (correlation coefficient ≥ 0.9996). If the concentrations of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol in the dietary supplements were less than 50.0 µg/mL, standard curves were prepared over a concentration range of 10.0–50.0 µg/mL. The within-day coefficients of variation for 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol at 50µg/mL were 2.54%, 2.38%, 2.55%, and 2.31%, respectively; at 100 µg/mL, they were 1.92%, 1.81%, 1.87%, and 1.74%, respectively.

The mean concentrations of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol in the ginger dietary supplements are shown in Table 2. The concentrations are the means of duplicate analyses of each ginger dietary supplement and are expressed on a milligram-per-gram basis and/or a milligram-per-capsule basis. The 6-gingerol concentration in the different ginger dietary supplements was higher than that of the 8-gingerol or 10-gingerol concentration, but not always higher than that of 6-shogaol. Across brands, the 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol concentrations varied widely. For example, the Nature's Plus ginger dietary supplement contained no 6-gingerol, 8-gingerol, or 10-gingerol, whereas the 6-gingerol concentration in the bulk ginger powder from Sun Harvest was 9.43 mg/g. One gram of ginger powder contained on average 2.56 ± 2.95, 1.27 ± 0.58, 0.47 ± 0.34, and 0.36 ± 0.51 mg (mean ± SD) of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol, respectively (Table 2). On a weight basis, 6-gingerol made up about 0.256% of the ginger powder, whereas the 6-shogaol, 8-gingerol, and 10-gingerol made up 0.127%, 0.047%, and 0.036%, respectively.


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  		Table 2. 6-Gingerol, 6-Shogaol, 8-Gingerol, and 10-Gingerol Composition of Ginger Dietary Supplements and USP Ginger Powder

 

The total amount of 6-gingerol in the recommended daily serving for each dietary supplement was calculated to determine if the total daily 6-gingerol amount might be more uniform across brands on this basis. Only 5 brands listed a daily dose. The amount of 6-gingerol in the recommended daily serving was calculated by multiplying the 6-gingerol concentration per capsule by the number of capsules to be taken per day as listed in Tables 1 and 2. Based on the recommended daily serving size, the total amounts of 6-gingerol ingested per day would be 0, 5.12, 5.58, 1.8, and 14.34 mg for Nature's Plus, Nature's Way, Nature's Herbs, Rexall, and Enzymatic Therapy, respectively.

The Enzymatic Therapy dietary supplement contained an extract of the ginger herb. As a result, its composition was placed on a milligram-per-capsule basis rather than on a milligram-per-gram basis as with the other ginger dietary supplements (Table 2). The capsules from Enzymatic Therapy were found to contain 4.78 mg of 6-gingerol, 10.23 mg of 6-shogaol, 2.43 mg of 8-gingerol, and 1.62 mg of 10-gingerol. The label stated that each capsule was standardized to contain 20.0 mg of 6-gingerol and 6-shogaol. The 6-shogaol concentration also was found to be very high relative to that of 6-gingerol, 8-gingerol, and 10-gingerol. This indicates that the 6-shogaol concentration of the ginger root was either very high or that dehydration of 6-gingerol had occurred during processing and/or storage.


   DISCUSSION
TOP
ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
The ginger root powder dietary supplements from different sources were found to vary widely in 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol composition. This was found when the concentrations were expressed on a milligram-per-gram basis or on a milligram-per-capsule basis. One brand did not contain any 6-gingerol, 8-gingerol, or 10-gingerol. The 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol concentrations of the ginger root powders varied 8.1-, 15.6-, 2.8-, and 3.9-fold, respectively. In addition, the amounts of 6-gingerol in the daily recommended doses varied from 0 to 14.34 mg. Based on these calculations, the amounts of 6-gingerol ingested per serving or per day would not compensate for the variation in the recommended serving sizes.

Except for the bulk ginger product, all of the labels on the containers listed the manufacturer, formulation, and, lot number. Three of the 10 ginger root dietary supplements did not list an expiration date, 5 did not list a daily serving size, and 7 were not standardized. The formulations of the different dietary supplements were fairly consistent in that 7 of 8 of the ginger dietary supplements contained either 530 or 550 mg of ginger root powder in each capsule. There was, however, a greater variation in the recommended serving size per day. The lowest serving size was 250 mg (Nature's Plus), whereas the 2 highest were 4.4 g per day (Nature's Way) and 4.77 g per day (Nature's Herbs). Thus, ginger dietary supplements must be added to the list of herbal preparations that vary widely in their composition, in their recommended serving size, in the total number of capsules to take per day, and in their lack of uniform standardization.

The variation in the gingerol composition and in the recommended daily serving size of the dietary supplements examined in this study could impact their use and acceptance as well as their efficacy and safety. The German Commission E Monograph recommends 1.0 g of ginger powder per day for treating loss of appetite, travel sickness, and dyspeptic complaints, but it does not recommend the use of ginger to treat morning sickness.16 The German Commission E, however, does recommend that 1.0 g of ginger powder per day be given for 4 days to treat hyperemesis gravidarum as suggested by Fischer-Rasmussen et al.3,16 One and 1.5 g per day of ginger powder and 0.5–1.0 g of ginger root extract for 3 days to 3 weeks were found to be safe and effective in treating nausea associated with pregnancy in the double-blind randomized clinical trials cited by Borelli et al7 and Boone and Shields.6 Caution should be exercised in following the doses recommended by health store employees. For example, the dose of ginger root dietary supplements recommended by health store employees for treating pregnancy-related nausea was found to vary widely and to be correct only 3.6% of the time.17 The labels on 4 of the dietary supplements examined in this study stated that the supplement can ease discomfort associated with travel, promote digestive health, support digestive health, and help maintain a calm stomach. None of the dietary supplements made a claim that the ginger powder can be used to reduce nausea associated with pregnancy. In light of the variation in composition and serving sizes of the different dietary supplements, we cannot recommend the use of ginger root dietary supplements as a treatment for nausea associated with pregnancy, nor can we recommend a given dose or duration of treatment.

The cause of the variation of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol composition is not known, but the variation could be due to the source and/or age of the ginger, the homogeneity of the rhizome used, or the method of processing. Even though 6-gingerol is the principal gingerol, we included information on 6-shogaol, 8-gingerol, and 10-gingerol compositions as well. The chromatographic profiles of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol might be used to standardize the ginger dietary supplements as well as the doses. Additionally, the chromatographic profiles might be useful in providing information on adulteration, quality of ginger rhizome, efficiency of extraction, and the effects of processing. In this regard, the ratio of 6-gingerol to 6-shogaol may serve as a marker of 6-gingerol stability and ginger quality. Fresh ginger, for example, contains very little 6-shogaol, but with heat and processing, 6-gingerol loses water and is converted to 6-shogaol.10,11. The source and quality of the ginger used in the clinical trials were not always given. Fresh ginger powder, for example, was used in 2 of the 4 clinical trials,2,7 yet we do not know if fresh ginger is better than ginger powder that is not fresh.

Chemical and chromatographic analyses of the ginger root powders and extracts used in clinical trials described in this report have not been performed. This represents a major limitation of those studies. Future clinical trials should include information on the amounts of 6-gingerol, 6-shogaol, 8-gingerol, and 10-gingerol in the ginger root powders and extracts. Information on other chemical substances should also be provided if these substances are found to be related to efficacy, safety, and quality of the ginger root dietary supplements. Our HPLC method is an excellent method for establishing such concentrations, and hopefully, such analyses will become standard practice in future clinical trials of dietary supplements. We would also recommend that the dose per day be expressed in as many ways as possible. For example, the dose might be expressed on the amount of 6-gingerol or the amount of total 6-, 8-, and 10-gingerol given per day as well as on the amount of ginger root powder or extract given per day. The duration of treatment also needs to be specified. Such information would more precisely identify the safest and most effective dose range. The variation that was found in the recommended daily dose of the ginger dietary supplements suggests that the recommended dose should be reevaluated and standardized as more definitive clinical data become available.

In this study, we analyzed only ginger dietary supplements that were available commercially. We did not evaluate the same ginger dietary supplement from different stores or with different lot numbers. Likewise, we did not evaluate products from international sources and the Internet. We did not determine the gingerol composition of fresh ginger powder, but we did analyze USP ginger powder as a reference source. The number of brands analyzed is relatively small but is believed to be representative of the ginger root powders. Lastly, we evaluated only 4 out of 50 or more constituents found in ginger root extracts. Further studies are needed to determine the appropriate dose of ginger root powders and extracts, the lower limits of effectiveness, the safety of the ginger root powders and the extracts, and the bioavailability and pharmacokinetics of the active ginger constituents.


   Footnotes
 
The views expressed in this article are those of the authors and do not reflect the official policy of the Department of Defense or other departments of the United States Government.

Corresponding author: Dr. Harvey A. Schwertner, 2200 Bergquist Drive, Lackland AFB, Texas; e-mail: harvey.schwertner{at}lackland.af.mil.

doi:10.1097/01.AOG.0000217697.33787.8c


   REFERENCES
TOP
ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
1. Kawai T, Kinoshita K, Koyama K, Takahashi K. Anti-emetic principles of Magnolia obovata bark and Zingiber officinale rhizome. Planta Med 1994;60:17–20.[Medline]

2. Vutyavanich T, Kraisarin T, Ruangsri R. Ginger for nausea and vomiting in pregnancy: randomized, double-masked, placebo-controlled trial. Obstet Gynecol 2001;97:577–82.[Abstract/Free Full Text]

3. Fischer-Rasmusssen W, Kjaer SK, Dahl C, Asping U. Ginger treatment of hyperemesis gravidarum. Eur J Obstet Gynecol Reprod Biol 1991;38:19–24.[Medline]

4. Keating A, Chez RA. Ginger syrup as an antiemetic in early pregnancy. Altern Ther Health Med 2002;8:89–91.[Medline]

5. Willetts KE, Ekangaki A, Eden JA. Effect of a ginger extract on pregnancy-induced nausea: a randomized controlled trial. Aust N Z J Obstet Gynaecol 2003;43:139–44.[Medline]

6. Boone SA, Shields KM. Treating pregnancy-related nausea and vomiting with ginger. Ann Pharmacother 2005;39:1710–3.[Abstract/Free Full Text]

7. Borrelli F, Capasso R, Aviello G, Pittler MH, Izzo AA. Effectiveness and safety of ginger in the treatment of pregnancy-induced nausea and vomiting. Obstet Gynecol 2005;105:849–56.[Abstract/Free Full Text]

8. Chrubasik S, Pittler MH, Roufogalis BD. Zingiberis rhizome: a comprehensive review on the ginger effect and efficacy profiles. Phytomedicine 2005;12:684–701.[Medline]

9. Nakazawa T, Ohsawa K. Metabolism of [6]-gingerol in rats. Life Sci 2002;70:2165–75.[Medline]

10. Chen CC, Ho CT. Chromatographic analyses of isomeric shogaol compounds derived from isolated gingerol compounds of ginger (Zingiber officinale roscoe). J Chromatogr 1986;360:175–84.

11. He X, Bernart MW, Lian L, Lin L. High-performance liquid chromatography-electrospray mass spectrometric analysis of pungent constituents of ginger. J Chromatogr 1998;796:327–34.

12. Shoji N, Iwasa A, Takemoto T, Ishida Y, Ohizumi Y. Cardiotonic principles of ginger. J Pharm Sci 1982;71:1174–5.[Medline]

13. Kiuchi F, Shibuya M, Sankawa U. Inhibition of prostaglandin and leukotreine biosynthesis by gingerols and diarylheptanoids. Chem Pharm Bull (Tokyo) 1992;40:387–91.[Medline]

14. Phan PV, Sohrabi A, Polotsky A, Hungerford DS, Lindmark L, Frondoza CG. Ginger extract components suppress induction of chemokine expression in human synoviocytes. J Altern Complement Med 2005;11:149–54.[Medline]

15. Kim EC, Min JK, Kim TY, Lee SJ, Yang HO, Han S, et al. 6-Gingerol, a pungent ingredient of ginger, inhibits angiogenesis in vitro and in vivo. Biochem Biophys Res Commun 2005;23:300–8.

16. Blumenthal M, Busse WR, Goldberg A, Gruenwald J, Hall T, Riggins W, et al, editors. The complete German Commission E monographs: therapeutic guide to herbal medicines. American Botanical Council, Austin, Texas. Boston (MA): Integrative Medicine Communications; 1998.

17. Buckner KD, Chavez ML, Raney EC, Stoehr JD. Health food stores' recommendations for nausea and migraines during pregnancy. Ann Pharmacother 2005;39:274–9.[Abstract/Free Full Text]





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