Rhubarb

What Is Rhubarb?

There are three species of rhubarb used medicinally (Rheum palmatum, R. tanguticum, and R. officinale), all found in temperate zones around the world.

Rhubarb rhizomes have a strong, bitter flavor, mostly as a result of their high anthraquinone content. These anthraquinones are also what gives rhubarb its laxative and astringent qualities.

It’s important to consider safety when using any herb with anthraquinones. It should only be used under the guidance of a trained practitioner if using this herb for anything more than as a bitter in small doses.

Other parts of the rhubarb plant, such as the brightly colored leaf stalks are popular for their tart flavor when making soups and pie.

What Is Rhubarb Used For?

Rhubarb is mainly used as a bitter in small doses to stimulate the flow of bile from the liver/gallbladder and to aid digestion. It’s also used for diarrhea in smaller doses, and for constipation in higher doses.

Traditional Uses

Western Herbal Medicine

It has been used traditionally as a mild stimulating tonic to the digestive mucous membrane, liver, and gall ducts, and removes mucous. In smaller doses, it was considered a hepatic, while large doses were used as a cathartic. ^{16Reference 16Hoffmann · 2003Medical herbalism: The science and practice of herbal medicine}.

Traditional Chinese Medicine

Pinyin: Dá Huáng

Taste: Bitter ^{17,18Reference 17Yang et al. · 2013Introduction to chinese materia medica (3rd ed.). (Pg 148-150)Reference 18Wu · 2005An illustrated Chinese materia medica}

Energy: Cold ^{17,18Reference 17Yang et al. · 2013Introduction to chinese materia medica (3rd ed.). (Pg 148-150)Reference 18Wu · 2005An illustrated Chinese materia medica}

Channels: Spleen, stomach, large intestine, liver, heart ^{18Reference 18Wu · 2005An illustrated Chinese materia medica}

Actions: Purges heat and accumulations, loosens bowels, promotes blood circulation, removes stagnation, drains fire, removes blood stasis and invigorates blood ^{2,3,4,17,18Reference 2Zhao et al. · 2011The Use of Response Surface Methodology to Optimize the Ultrasound-Assisted Extraction of Five Anthraquinones from Rheum palmatum LView study →Reference 3Chen et al. · 2009Mechanisms of therapeutic effects of rhubarb on gut origin sepsisReference 4Feng · 2000Mechanism of Rhubarb in preventing the occurrence of gastrointestinal function failureReference 17Yang et al. · 2013Introduction to chinese materia medica (3rd ed.). (Pg 148-150)Reference 18Wu · 2005An illustrated Chinese materia medica}.

Indications: Constipation due to heat accumulation, accumulation in intestine, abdominal pain, damp-heat jaundice, blood heat hemorrhage, red eyes, sore throat, intestinal abscesses, swellings, sores, and ulcers ^{17Reference 17Yang et al. · 2013Introduction to chinese materia medica (3rd ed.). (Pg 148-150)}.

Botanical Information

Rhubarb is a member of the Polygonaceae family of plants. This family is also referred to as the buckwheat family. There are 1200 species in this family, and about 48 genera.

Other notable members of this family include Rumex crispus (yellow dock), and Fagopyrum esculentum (buckwheat).

Habitat, Ecology & Distribution

Although various species of rhubarb are cultivated all over the world, it’s mainly found naturally in Northern China and Tibet.

Harvesting, Collection & Preparation

Rhubarb proliferates quickly and can reach heights of up to 3m high, only to die back to the soil each winter. Rhubarb is an easy garden vegetable/medicine species and is easy to cultivate in both shady, and sunny locations.

Pharmacology & Medical Research

Blood-Brain Barrier Attenuation

Rhubarb is reported to attenuate the BBB after hemorrhagic stroke in rats. The mechanism of action was suggested to be through increased zonula-occludens-1 expression ^{9Reference 9Wang et al. · 2016AnimalRhubarb attenuates blood-brain barrier disruption via increased zonula occludens-1 expression in a rat model of intracerebral hemorrhageView study →}. This may prove a useful medicine for neuroprotection in intracerebral hemorrhages in the future, more research is needed.

Laxative

The laxative actions of rhubarb were investigated in a rat model. The study found that rhubarb (Rheum palmatum) influenced ion transport (Na+ and Cl-) across the rat ileum epithelia ^{1Reference 1Tsai et al. · 2004AnimalEffect of Ethanol Extracts of Three Chinese Medicinal Plants with Laxative Properties on Ion Transport of the Rat Intestinal EpitheliaView study →}.

Anthraquinone’s, which are contained in rhubarb root in high amounts are well known to produce laxative effects within the body ^{13Reference 13Sakulpanich et al. · 2009Determination of anthraquinone glycoside content in Cassia fistula leaf extracts for alternative source of laxative drug}. This effect is thought to be due to stimulation of the intestinal musculature, probably via prostaglandin mediation, and typically takes 8–14 hours after ingestion to occur.

Kidney Protective

Rhubarb has been shown to have a beneficial effect on chronic and acute renal failure in vivo ^{10,11Reference 10Jha · 2010Herbal medicines and chronic kidney diseaseReference 11Zhong et al. · 2013Therapeutic use of traditional Chinese herbal medications for chronic kidney diseases}.

It’s been found to have the ability to reduce proteinuria, as well as generally improve renal function when used alone. Synergy has been suggested for this action when used with angiotensin-converting enzyme inhibitors ^{11Reference 11Zhong et al. · 2013Therapeutic use of traditional Chinese herbal medications for chronic kidney diseases}.

In a study investigating the protective effects of 4 rhubarb extracts on HgCl2-induced acute renal failure (ARF) found that the anthraquinone containing extract had significant protective actions on the kidneys using this model ^{14Reference 14Gao et al. · 2016AnimalRhubarb Anthraquinones Protect Rats against Mercuric Chloride (HgCl2)-Induced Acute Renal FailureView study →}. More research is needed to determine whether this effect is exclusive to rhubarb, or if other anthraquinone containing herbs can achieve the same action.

Phytochemistry

Rhubarb’s pharmacology is driven by two opposing groups of phenolics. The laxative action comes from its anthraquinones — chiefly rhein, emodin, aloe-emodin, chrysophanol, and physcion — which occur both free and as glycosides and stimulate colonic motility roughly 8–14 hours after ingestion ^{13Reference 13Sakulpanich et al. · 2009Determination of anthraquinone glycoside content in Cassia fistula leaf extracts for alternative source of laxative drug}. In a representative free-anthraquinone extract of R. palmatum, rhein, emodin, and aloe-emodin dominated the profile (~43%, ~27%, and ~15% of the extract respectively), with chrysophanol, physcion, and the dianthrone glycoside sennoside A present at lower levels ^{19Reference 19Wu et al. · 2017AnimalPharmacokinetics and pharmacodynamics of rhubarb anthraquinones extract in normal and disease rats (extract composition: rhein 42.95%, emodin 26.72%, aloe-emodin 14.69%, sennoside A 3.91%, chrysophanol 1.50%, physcion 0.49%)View study →}.

Counterbalancing the purgative anthraquinones is a substantial pool of tannins — gallotannins and catechin-derived compounds such as gallic acid and catechin. R. palmatum root is unusually tannin-rich (around 11%, versus roughly 4–7% in other rhubarb species) ^{20Reference 20Grieve · 1931A Modern Herbal — RhubarbsView study →}. This astringent fraction explains why small doses bind the stool and check diarrhoea, while larger doses let the anthraquinones drive a laxative effect.

Constituent Summary

Figures are share of a representative free-anthraquinone extract (anthraquinones) or share of dried root (tannins); both vary widely with species, growing region, and preparation. Browse a class to see related compounds, or any compound for its full profile.

Clinical Applications

Rhubarb is reliable for promoting a change in bowel movements. It can be used on the smaller end of the dosage for treating diarrhea, and on the higher end of the dosage for constipation. Additionally, the intense bitter flavour of rhubarb makes it useful in small doses as a bitter for stimulating digestion and liver function.

One area deeming further research is for its ability to attenuate the blood brain barrier. This may be a useful mechanism for antipsychotic medications, nervines, and nootropics in the future.

Cautions & Safety

Avoid rhubarb if taking medications for a heart condition or medications that affect potassium loss through the kidneys.

May increase the effect of cardiac glycosides and interact with antiarrhythmic drugs through promoting the loss of potassium ^{16Reference 16Hoffmann · 2003Medical herbalism: The science and practice of herbal medicine}.

May decrease the absorption of other drugs through a decrease in transit time. ^{16Reference 16Hoffmann · 2003Medical herbalism: The science and practice of herbal medicine}.

May discolor the urine with a red or yellow hue. ^{16Reference 16Hoffmann · 2003Medical herbalism: The science and practice of herbal medicine}.

Synergy

Synergy has been suggested for rhubarb’s kidney protective actions when used with angiotensin-converting enzyme inhibitors ^{11Reference 11Zhong et al. · 2013Therapeutic use of traditional Chinese herbal medications for chronic kidney diseases}.

This may include herbs such as Camellia sinensis, Hibiscus sabdariffa, Vaccinum mytrillus, or Cryptomeria japonica ^{15Reference 15Nileeka Balasuriya B.W et al. · 2011Plant flavonoids as angiotensin converting enzyme inhibitors in regulation of hypertension}.

References

1. Tsai, J., Tsai, S., & Chang, W. (2004). Effect of Ethanol Extracts of Three Chinese Medicinal Plants with Laxative Properties on Ion Transport of the Rat Intestinal Epithelia. Biol. Pharm. Bull, 27(2), 162-165. doi:10.1248/bpb.27.162
2. Zhao, L., Liang, J., Li, W., Cheng, K., Xia, X., Deng, X., & Yang, G. (2011). The Use of Response Surface Methodology to Optimize the Ultrasound-Assisted Extraction of Five Anthraquinones from Rheum palmatum L. Molecules, 16(12), 5928-5937. doi:10.3390/molecules16075928
3. Chen, D.C.; Wang, L. (2009). Mechanisms of therapeutic effects of rhubarb on gut origin sepsis. Chin. J. Traumatol. 12, 365-369.
4. Feng, S. (2000). Mechanism of Rhubarb in preventing the occurrence of gastrointestinal function failure. Zhongguo Zhong Xi Yi Jie He Za Zhi 20, 795-797.
5. Barceloux, D.G. (2009). Rhubarb and oxalosis (Rheum species). Dis. Mon. 55, 403-411.
6. Chai; Y.F.; Ji, S.G.; Wu, Y.T.; Liang, D.S.; Xu, Z.M. (1998). The separation of anthraquinone derivatives of rhubarb by miceller electrokinetic capillary chromatography. Biomed. Chromatogr. 12, 193-195.
7. Zhou, X.; Song, B.; Jin, L.; Hu, D.; Diao, C.; Xu, G.; Zou, Z.; Yang, S. (2006). Isolation and inhibitory activity against ERK phosphorylation of hydroxyanthraquinones from rhubarb. Bioorg. Med. Chem. Lett. 16, 563-568.
8. Ji, S.G.; Chai, Y.F.; Wu, Y.T.; Yin, X.P.; Xiang, Z.B.; Liang, D.S.; Xu, Z.M.; Li, X. (1998). Separation and determination of anthraquinone derivatives in rhubarb and its preparations by micellar electrokinetic capillary chromatography. Biomed. Chromatogr. 12, 335-337.
9. Wang, Y., Peng, F., Xie, G., Chen, Z., Li, H., Tang, T., & Luo, J. (2016). Rhubarb attenuates blood-brain barrier disruption via increased zonula occludens-1 expression in a rat model of intracerebral hemorrhage. Experimental and Therapeutic Medicine. doi:10.3892/etm.2016.3330
10. Jha, V. (2010). Herbal medicines and chronic kidney disease. Nephrology 15, 10–17.
11. Zhong, Y.; Deng, Y.; Chen, Y.; Chuang, P.Y.; He, J.C. (2013). Therapeutic use of traditional Chinese herbal medications for chronic kidney diseases. Kidney Int. 84, 1108–1118.
12. Ye, M.; Guo, D.A.; Han, J.; Chen, H.B.; Zheng, J.H. (2007). Analysis of phenolic compounds in Rhubarbs using liquid chromatography coupled with electrospray ionization mass spectrometry. J. Am. Soc. Mass Spectr. 18, 82–91.
13. Sakulpanich, A.; Gritsanapan, W. (2009). Determination of anthraquinone glycoside content in Cassia fistula leaf extracts for alternative source of laxative drug. Int. J. Biomed. Pharm. Sci. 3, 42–45.
14. Gao, D., Zeng, L., Zhang, P., Ma, Z., Li, R., Zhao, Y. Wang, J. (2016). Rhubarb Anthraquinones Protect Rats against Mercuric Chloride (HgCl2)-Induced Acute Renal Failure. Molecules, 21(3), 298. doi:10.3390/molecules21030298
15. Nileeka Balasuriya B.W, and Vasantha Rupasinghe H.P. (2011). Plant flavonoids as angiotensin converting enzyme inhibitors in regulation of hypertension. Functional Foods in Health and Disease. 5:172-188
16. Hoffmann, D. (2003). Medical herbalism: The science and practice of herbal medicine. Rochester, VT: Healing Arts Press.
17. Yang, J., Huang, H., Zhu, Li-Jiang, & Chen, Y. (2013). Introduction to chinese materia medica (3rd ed.). (Pg 148-150).
18. Wu, J. N. (2005). An illustrated Chinese materia medica. New York: Oxford University Press. (Pg. 552-553).
19. Wu, W., Hu, N., Zhang, Q., Li, Y., Li, P., Yan, R., & Wang, Y. (2017). Pharmacokinetics and pharmacodynamics of rhubarb anthraquinones extract in normal and disease rats (extract composition: rhein 42.95%, emodin 26.72%, aloe-emodin 14.69%, sennoside A 3.91%, chrysophanol 1.50%, physcion 0.49%). Biomedicine & Pharmacotherapy, 91, 425–435. doi:10.1016/j.biopha.2017.04.109
20. Grieve, M. (1931). A Modern Herbal — Rhubarbs. Retrieved from https://www.botanical.com/botanical/mgmh/r/rhuba14.html (R. palmatum tannin content ~11% vs ~4–7% in other species).