Elsevier

Phytochemistry

Volume 65, Issue 13, July 2004, Pages 1937-1954
Phytochemistry

Fresh organically grown ginger (Zingiber officinale): composition and effects on LPS-induced PGE2 production

https://doi.org/10.1016/j.phytochem.2004.06.008Get rights and content

Abstract

Gas chromatography in conjunction with mass spectrometry, a technique previously employed to analyze non-volatile pungent components of ginger extracts modified to trimethylsilyl derivatives, was applied successfully for the first time to analyze unmodified partially purified fractions from the dichloromethane extracts of organically grown samples of fresh Chinese white and Japanese yellow varieties of ginger, Zingiber officinale Roscoe (Zingiberaceae). This analysis resulted in the detection of 20 hitherto unknown natural products and 31 compounds previously reported as ginger constituents. These include paradols, dihydroparadols, gingerols, acetyl derivatives of gingerols, shogaols, 3-dihydroshogaols, gingerdiols, mono- and diacetyl derivatives of gingerdiols, 1-dehydrogingerdiones, diarylheptanoids, and methyl ether derivatives of some of these compounds. The thermal degradation of gingerols to gingerone, shogaols, and related compounds was demonstrated. The major constituent in the two varieties was [6]-gingerol, a chemical marker for Z. officinale. Mass spectral fragmentation patterns for all the compounds are described and interpreted. Anti-inflammatory activities of silica gel chromatography fractions were tested using an in vitro PGE2 assay. Most of the fractions containing gingerols and/or gingerol derivatives showed excellent inhibition of LPS-induced PGE2 production.

Ginger extracts were analyzed directly by GC–MS without modification to trimethylsilyl ether derivatives. From organically grown Hawaiian white and yellow ginger varieties 51 compounds were identified, of which 20 had not been previously reported as ginger constituents.

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Introduction

Chronic obstructive pulmonary disease, asthma and rheumatoid arthritis are associated with chronic inflammation. Treatment of these diseases with therapeutic pharmaceuticals has met with some success. In addition, patients suffering from diseases with associated chronic inflammation are turning to alternatives for relief of their symptoms or as prophylactic treatments. These alternatives include dietary supplements that have been purported to have anti-inflammatory actions. However, the efficacy and the potency of these supplements have not been studied in great detail nor have the active compounds been identified.

Ginger [Zingiber officinale Roscoe (Zingiberaceae)] and supplements derived from ginger have received attention for the treatment of chronic inflammation. Administration of ginger has resulted in decreased symptoms of rheumatoid arthritis (Srivastava and Mustafa, 1992) and gingerol (a component of ginger) has been reported to have anti-inflammatory actions, which include suppression of both cyclooxygenase and lipooxygenase metabolites of arachidonic acid (Kiuchi et al., 1992; Srivas, 1984; Tjendraputra et al., 2001).

Previous quantitative analyses of ginger have shown that gingerols, a family of homologous compounds differentiated by the number of carbon atoms in their side chain, are the major pungent constituents, with [6]-gingerol [5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)decan-3-one] being the most abundant (Govindarajan, 1982). Another homologous series which also accounts for the pungency of ginger is the shogaol family, the dehydrated form of the gingerols, resulting from the elimination of the OH group at C-5 with the formation of a double bond between C-4 and C-5. The shogaols are known to occur naturally and also are formed chemically from the corresponding gingerols in pH 2.5–7.2 media and during thermal processing, long-term storage and chromatography over silica gel and alumina (Connell and Sutherland, 1969; Mustafa et al., 1993). The distinct aroma of fresh ginger comes from the volatile oils, the second major group of components of ginger. The presence of these volatile oils, which were not investigated in this study, makes the separation of minor non-volatile pungent components difficult.

Various analytical techniques employing chromatographic methods such as GLC and GC in conjunction with mass spectroscopy have been used to analyze pungent components in ginger by modifying the ginger extract and/or partially purified fractions to their trimethylsilyl (TMS) derivatives with a view to improve their volatility, stability and separation (Masada et al., 1973; Clark et al., 1977; Harvey, 1981; Masada et al., 1974). More recently, He et al. (1998) described the analysis of ginger constituents by the combination of high pressure liquid chromatography with UV photodiode array detection and electrospray mass spectrometry (HPLC–UV–ESMS).

We have separated organic extracts from Chinese white and Japanese yellow ginger rhizomes by silica gel chromatography, finding many fractions which have in vitro anti-inflammatory activity. GC–MS analysis of the underivatized active fractions provided excellent resolution of the sixty three (163) components, most of which could be identified from their mass spectral fragmentations. These included 31 previously reported ginger constituents, 20 new natural products, and 12 artifacts produced by thermal degradation of the gingerols. Some of the active fractions contained little or no gingerols, but these contained gingerol derivatives.

Section snippets

Results and discussion

Only those CC fractions that demonstrated anti-inflammatory activity in the PGE2 assay were subjected to GC–MS analysis to detect and identify the constituents present in them. The yields of the CC fractions from GF2-00 and GF3-00, their PGE2 assay profile and the broad spectrum of compounds detected are summarized in Table 1. Individual compounds (156) identified are listed in Table 2 together with their MS (molecular ion and base peaks) characteristics, while thermal degradation products (57

PGE2 production and cytotoxicity

Of the CC fractions analyzed for biological activity, cytotoxicity only occurred at fairly high doses (greater than 50 μg/ml; Table 1). Therefore, inhibition of PGE2 production was not due to the toxicity of the fractions. All of the fractions analyzed had high activity (IC50 between 50 and 100 ng/ml). This is comparable to the IC50 for indomethacin in our assay system. Tjendraputra et al. (2001) have demonstrated that pure compounds found in ginger have varying abilities to inhibit PGE2

Plant material

Chinese white and Japanese yellow ginger seed rhizomes were planted in March 2002 and the resulting plants were grown amended only with organic fertilizer at Hilo Hawaii for the next several months. Mature rhizomes from these plants were harvested in March 2003, two days prior to shipment to Tucson, Arizona, for storage (two weeks at 4 °C) and subsequent chemical analysis.

Extraction

Rhizomes of the yellow variety (GF3, 3.3 kg) were sliced into small pieces, blended with MeOH (10 l) and stirred

Acknowledgements

This work was supported by the National Institutes of Health ODS/NCCAM (Grant #5 P50 AT000 474-04 to B.N.T.). We wish to thank Dr. David Gang of the University of Arizona, Department of Plant Sciences, Hugh Johnson of Puna Organics and Dean Pinner of Pinner Creek Organics for generous gifts of organic white and organic yellow ginger rhizomes. We are grateful to Veronica Rodriguez for HPLC analyses and Mark Yanagihashi for preparing tables and other technical assistance.

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