Rheum palmatum, commonly known as Chinese rhubarb or Turkish rhubarb, is a perennial herb from the Polygonaceae family, native to the regions of western China and the Tibetan Plateau. Known for its large, palmate leaves and striking red stems, this plant has been cultivated for its medicinal properties for centuries, particularly in traditional Chinese medicine.

Botanical Classification

Kingdom: Plantae
Clade: Angiosperms
Class: Eudicots
Order: Caryophyllales
Family: Polygonaceae
Genus: Rheum
Species: R. palmatum

Plant Characteristics

Rheum palmatum can grow up to 2-3 meters in height, featuring deep red to purple stems and large leaves that can reach up to 40-50 cm across. The plant produces tall flower spikes in late spring to early summer, which are creamy white to red in color, creating a dramatic visual display. It is a robust plant, capable of surviving in harsh climates with poor soil conditions.

Chemical Composition and Structure

The roots of Rheum palmatum contain anthraquinones, tannins, and several important bioactive compounds such as emodin and rhein. These substances are known for their potent laxative effects and have been studied for their potential anti-inflammatory and anticancer properties.

How to Cultivate It

1. Soil: Prefers well-drained, fertile soil, but is quite adaptable to less ideal conditions.
2. Light: Grows best in full sun but can tolerate partial shade.
3. Water: Needs regular watering, especially in dry conditions, but is relatively drought-tolerant once established.
4. Temperature: Thrives in a range of temperatures but requires some protection from extreme cold.

Uses and Benefits

Rheum palmatum is primarily used for its medicinal properties. The dried roots are used in traditional medicine to treat constipation, digestive disorders, and as a detoxifying agent. The plant is also studied for its potential benefits in treating chronic metabolic diseases due to its antioxidant properties.

Applications

• Medicinal: The roots are processed into powders, tinctures, and extracts used in various herbal remedies.
• Culinary: While not as commonly used in cooking as its relative, garden rhubarb, the young stems of Rheum palmatum can be used in similar ways, provided they are properly prepared to remove toxins.
• Ornamental: With its striking appearance, it is also cultivated as an ornamental plant in gardens.

Environmental and Safety Considerations

Rheum palmatum should be grown with care, as the plant contains compounds that can be toxic if not prepared correctly. It is important for gardeners and herbalists to handle the plant with knowledge of its medicinal and toxic properties. Environmental impact is minimal, but cultivation should be managed to prevent it from becoming invasive in non-native areas. As with any medicinal plant, use should be guided by a healthcare provider, especially in therapeutic contexts.

References__________________________________________________________________________

Nguyen LTH, Ahn SH, Shin HM, Yang IJ. Anti-Psoriatic Effect of Rheum palmatum L. and Its Underlying Molecular Mechanisms. Int J Mol Sci. 2022 Dec 15;23(24):16000. doi: 10.3390/ijms232416000. 

Abstract. Psoriasis is a chronic, immune-mediated inflammatory skin disorder. Rheum palmatum L. is a common traditional medicinal herb with anti-inflammatory and immunomodulatory activities. This study aimed to investigate the anti-psoriatic effects of the ethanolic extract from R. palmatum L. (RPE) and its chemical constituents, as well as the mechanisms underlying their therapeutic significance. An imiquimod (IMQ)-induced psoriasis-like mouse model was used to examine the anti-psoriatic effect of RPE in vivo. Network pharmacological analysis was performed to investigate the potential targets and related pathways of the RPE components, including rhein, emodin, chrysophanol, aloe-emodin, and physcion. The anti-inflammatory effects and underlying mechanisms of these components were examined using in vitro models. Topical application of RPE alleviated psoriasis-like symptoms and reduced levels of inflammatory cytokines and proliferation markers in the skin. Network pharmacological analysis revealed that RPE components target 20 genes that are linked to psoriasis-related pathways, such as IL-17, MAPK, and TNF signaling pathways. Among the five components of RPE, rhein and emodin showed inhibitory effects on TNF-α and IL-17 production in EL-4 cells, attenuated the production of CXCL8, CXCL10, CCL20, and MMP9, and reduced proliferation in HaCaT cells. Chrysophanol, aloe-emodin, and physcion were less effective than rhein and emodin in suppressing inflammatory responses and keratinocyte proliferation. The effects of these compounds might occur through the inhibition of the ERK, STAT3, and NF-κB signaling pathways. This study suggested the anti-psoriatic effect of RPE, with rhein and emodin as the main contributors that regulate multiple signaling pathways.

Shang X, Dai L, He J, Yang X, Wang Y, Li B, Zhang J, Pan H, Gulnaz I. A high-value-added application of the stems of Rheum palmatum L. as a healthy food: the nutritional value, chemical composition, and anti-inflammatory and antioxidant activities. Food Funct. 2022 May 10;13(9):4901-4913. doi: 10.1039/d1fo04214a. 

Abstract. Rhubarb has edible stems or stalks. In this paper, we investigated the nutritional value, chemical composition, and bioactivities of Rheum palmatum stems (SRP) and analyzed the mode of action. SRP exhibited biosafety and had nutritional value, with abundant essential amino acids and minerals. Based on network pharmacology and western blot tests, we found that it showed anti-inflammatory activity via the PI3K-Akt-mediated NF-κB pathway. Out of 20 compounds identified using UPLC-ESI-Q-TOF/MS analysis, cirsiliol and hydrangenol were active compounds and they inhibited NO production in RAW264.7 cells induced by LPS. The alleviation of an inflammatory response is combined with a decrease in oxidative stress, and SRP showed antioxidant activity via attenuating antioxidant enzymes, scavenging free radicals, improving the mitochondrial membrane potential, and decreasing the reactive oxygen species level. These results indicated that SRP, with abundant flavonoids and a good nutritional composition, could be used as a dietary supplement for food applications.

Xiong Y, Kim HK, Özer ÖÇ, van Duijn B, Korthout HAAJ, Zi L, Cai A. Synergistic Inhibiting Effect of Phytochemicals in Rheum palmatum on Tyrosinase Based on Metabolomics and Isobologram Analyses. Molecules. 2023 Jan 17;28(3):944. doi: 10.3390/molecules28030944. 

Abstract. Tyrosinase (TYR) plays a key role in the enzymatic reaction that is responsible for a range of unwanted discoloration effects, such as food browning and skin hyperpigmentation. TYR inhibitors could, therefore, be candidates for skin care products that aim to repair pigmentation problems. In this study, we used a metabolomics approach combined with the isobologram analysis to identify anti-TYR compounds within natural resources, and evaluate their possible synergism with each other. Rheum palmatum was determined to be a model plant for observing the effect, of which seven extracts with diverse phytochemicals were prepared by way of pressurized solvent extraction. Each Rheum palmatum extract (RPE) was profiled using nuclear magnetic resonance spectroscopy and its activity of tyrosinase inhibition was evaluated. According to the orthogonal partial least square analysis used to correlate phytochemicals in RPE with the corresponding activity, the goodness of fit of the model (R2 = 0.838) and its predictive ability (Q2 = 0.711) were high. Gallic acid and catechin were identified as the active compounds most relevant to the anti-TYR effect of RPE. Subsequently, the activity of gallic acid and catechin were evaluated individually, and when combined in various ratios by using isobologram analysis. The results showed that gallic acid and catechin in the molar ratios of 9:5 and 9:1 exhibited a synergistic inhibition on TYR, with a combination index lower than 0.77, suggesting that certain combinations of these compounds may prove effective for use in cosmetic, pharmaceutical, and food industries.

Wang H, Song H, Yue J, Li J, Hou YB, Deng JL. Rheum officinale (a traditional Chinese medicine) for chronic kidney disease. Cochrane Database Syst Rev. 2012 Jul 11;2012(7):CD008000. doi: 10.1002/14651858.CD008000.pub2. 

Abstract. Background: Chronic kidney disease (CKD) is a major public health issue worldwide. Standard therapies to delay CKD progression include dietary protein restriction and administration of angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) to help control blood pressure and confer additional renoprotective effects. Despite such interventions, CKD incidence and mortality rates continue to increase. Rheum officinale (Da Huang) a medicinal herb used widely in China to treat CKD has been reported to offer a range of pharmacological properties that may delay disease progression. Objectives: To assess the benefits and harms of Rheum officinale for preventing the progression of CKD.....Main results: We identified nine studies that enrolled 682 participants. None of the studies reported blinding or group allocation methods. Seven studies were judged to be at low risk of incomplete outcome reporting; three studies were judged to be a low risk of selective reporting (protocols were available and/or all outcomes relevant to the this review were reported); and two studies were judged free of other potential biases.Seven studies compared Rheum officinale with no treatment and two made comparisons with captopril, an angiotensin-converting enzyme inhibitor (ACEi). Compared with no treatment, Rheum officinale had a positive effect on SCr (MD -87.49 µmol/L, 95% CI -139.25 to -35.72) and BUN (MD -10.61 mmol/L, 95% CI -19.45 to -2.21). Compared with captopril, a statistically significant difference was not demonstrated in relation to Rheum officinale for any outcome (BUN, CrCl, or patients' capacity to undertake work). No data were available on all-cause mortality or cost of treatment. Only minor adverse events were reported in association with Rheum officinale. Authors' conclusions: Currently available evidence concerning the efficacy of Rheum officinale to improve SCr and BUN levels in patients with CKD is both scant and low quality. Although Rheum officinale does not appear to be associated with serious adverse events among patients with CKD, there is no current evidence to support any recommendation for its use.

Tan ZB, Fan HJ, Wu YT, Xie LP, Bi YM, Xu HL, Chen HM, Li J, Liu B, Zhou YC. Rheum palmatum extract exerts anti-hepatocellular carcinoma effects by inhibiting signal transducer and activator of transcription 3 signaling. J Ethnopharmacol. 2019 Mar 25;232:62-72. doi: 10.1016/j.jep.2018.12.019. Epub 2018 Dec 13. PMID: 30553869.