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Rheum palmatum

Rheum palmatum, commonly known as Chinese rhubarb, is a herbaceous perennial plant in the family, characterized by its large, basal of round to subcircular leaves that are palmately lobed with 3–5 primary divisions, each up to 40–60 cm in diameter, and supported by long petioles. The plant grows 1.5–3 m tall, featuring hollow, erect stems that bear dense panicles of small, pink to red flowers blooming from May to , followed by winged fruits. Native to temperate regions, it thrives in organically rich, moist, well-drained soils in full sun to part shade, forming clumps up to 1.8–3 m wide. This species is primarily distributed across mountainous forest margins in northwestern and , including provinces such as , , , and , as well as , with introduced populations in areas like and . It is found in high-altitude mountainous regions, such as forest margins and rocky slopes in and , where it has been cultivated for medicinal purposes for over 2,000 years. The rhizomes and roots of R. palmatum are the primary medicinal parts, harvested after 3–4 years of growth and used in since at least 270 BCE for their anthraquinone-rich content, including , , and chrysophanol, which contribute to , antibacterial, , and anticancer effects. Pharmacological studies highlight its roles in treating , gastrointestinal disorders, sepsis-induced injuries, and chronic conditions like high and peptic ulcers, often through mechanisms such as inhibiting pathways and promoting . While valued ornamentally for its bold foliage and environmental benefits in , the leaves are toxic and not edible, distinguishing it from culinary species.

Taxonomy

Classification

Rheum palmatum is classified in the kingdom Plantae, Tracheophyta, Magnoliopsida, Caryophyllales, Polygonaceae, genus , and palmatum. The species was first described by in his , tenth edition, published in 1759. Within the genus , which comprises approximately 60 herbaceous perennial species primarily distributed in temperate , R. palmatum belongs to section Palmata, as established by Agnia Losina-Losinskaja in the 1936 Flora SSSR. This sectional classification was later confirmed in the 1998 Flora Reipublicae Popularis Sinicae by A. R. Li, who recognized eight sections in the genus based on morphological and phylogenetic characteristics. R. palmatum exhibits a stable diploid chromosome number of 2n = 22, with a karyotype consisting of 20 metacentric and 2 submetacentric chromosomes. The genus Rheum includes several closely related species, notably R. officinale and R. tanguticum (R. tanguticum is sometimes considered a variety of R. palmatum but is now widely accepted as a distinct species), all within section Palmata and native primarily to China (with R. palmatum also occurring in northern Vietnam). Taxonomic distinctions among these are primarily based on leaf morphology: R. officinale has shallowly lobed leaves, while R. palmatum features leaves deeply divided into 5–9 lobes, and R. tanguticum has leaves segmented into linear lobes; however, intermediate forms complicate clear delineation between R. palmatum and R. tanguticum.

Etymology

The genus name Rheum originates from the ancient Greek term rha or rheum, which referred to rhubarb-like plants imported from eastern regions, possibly linked to the Volga River (anciently called Rha) where early specimens were thought to grow or from which they were traded. The specific epithet palmatum derives from the Latin palmatus, meaning "shaped like an open hand" or "palmate," describing the plant's distinctive hand-like, lobed leaves. Carl Linnaeus first described Rheum palmatum in his 1759 work Systema Naturae (tenth edition), basing the name on a brief diagnostic phrase emphasizing the "subpalmatis" (nearly palmate) foliage. Common names for Rheum palmatum reflect its cultural and trade history. In , it is known as dahuang (大黄), literally translating to "great yellow" or "big yellow," alluding to the plant's large, yellowish rootstocks used in . English common names include rhubarb, directly tied to its native Asian origins; ornamental rhubarb, emphasizing its bold, decorative leaves in gardens; and trade-derived terms like rhubarb and East Indian rhubarb, which arose during medieval commerce to mask the true source in and by associating it with transit routes through and .

Description

Physical characteristics

Rheum palmatum is a herbaceous perennial that grows to 1.5–2 m in height, though specimens in cultivation can reach up to 2.5 m. It features a stout, woody rhizomatous rootstock from which thick, deep, branched roots emerge, serving both as a storage organ and a means of vegetative propagation through division. The plant forms a basal rosette of large leaves, which are subcircular to cordate at the base and palmately divided into pinnatisect lobes, measuring 40–60 cm long and wide, with some reaching up to 100 cm in cultivation. These leaves have an acuminate or narrowly acute apex, five basal veins, and are abaxially densely pubescent while adaxially sulcate to papilliferous, supported by thick petioles that contribute to the plant's domed foliage mound spanning 1–1.8 m wide. The erect stem is hollow, sulcate, and subglabrous or muricate at the nodes, rising above the foliage to support the reproductive structures. In summer, it produces large, branched panicles up to 1.5 m tall, with connivent, densely pubescent branches bearing small flowers. The flowers are tiny, with six tepals that are typically purple-red but occasionally yellow-white; the outer three tepals are elliptic to orbicular and 1–1.5 mm long, while the stamens do not exceed the length. The is rhomboid-ovoid, with a slightly deflexed and inflated , leading to oblong-ellipsoid fruits measuring 8–9 × 7–7.5 mm with retuse ends and narrow wings. Compared to the rhubarb (Rheum × hybridum), R. palmatum is distinguished by its much larger overall size and more deeply palmately lobed leaves with oblong, sharpish segments, whereas varieties exhibit smaller stature and broader, less divided, heart-shaped leaves.

Karyotype

_Rheum palmatum exhibits a diploid complement with a basic number of x = 11, resulting in $2n = 22. Cytogenetic analysis reveals a formula of $2n = 22 = 20m + 2sm, consisting of 20 metacentric and 2 submetacentric s, with lengths ranging from 1.72 to 2.78 μm. This configuration demonstrates high symmetry, classified as Stebbins' 1A type, with a mean centromeric index of approximately 44.35% and a asymmetry index of 55.39%. The of R. palmatum shows remarkable stability, with 96% of observed cells maintaining the $2n = 22 count across examined samples, and no evidence of or structural aberrations such as satellite markers. Broader cytogenetic surveys of the confirm this uniformity, as R. palmatum shares the same symmetric, predominantly metacentric (mean length ~2.35 μm) with other in the Qinghai-Tibetan Plateau , indicating minimal differentiation despite morphological diversity. Within the genus Rheum, the conserved diploid of R. palmatum facilitates potential hybridization, as evidenced by multiple (ITS) copies in related species, suggesting reticulate evolution and . However, represents a significant evolutionary mechanism, with tetraploid species ( $2n = 44 ) arising possibly through hybridization events, driving and diversification in this rapidly radiating lineage while the uniform morphology limits structural barriers to interspecific crosses.

Similar species

_Rheum palmatum differs from the closely related Rheum officinale in leaf morphology and flower coloration. While both species reach similar heights of 1.5-2 m, R. palmatum features basal leaves that are palmately divided into deeply pinnatisect lobes, with blades 40-60 cm wide and five prominent basal veins, whereas R. officinale has orbicular to broadly ovate blades that are palmatilobate with shallower lobes and 5-7 basal veins. Additionally, R. palmatum produces purple-red flowers, in contrast to the green to yellow-white flowers of R. officinale. Their native ranges also diverge, with R. officinale primarily found in southwestern China, such as Sichuan, while R. palmatum occurs more broadly across central and northern regions. Rheum tanguticum is morphologically similar to R. palmatum but exhibits more pronounced leaf dissection and a preference for higher altitudes. Leaves of R. tanguticum are palmately 5-lobed, with the middle three lobes pinnatisect into narrower segments, compared to the pinnatisect but less intricately divided lobes of R. palmatum. Both share purple-red flowers and stout roots, but R. tanguticum typically grows at 1600-3000 m in , occupying higher and cooler niches than the broader 1500-4400 m range of R. palmatum. In distinction from the cultivated edible garden rhubarb, Rheum rhabarbarum, R. palmatum exhibits a larger stature, reaching 1.5-2 m compared to 0.5-1.5 m for R. rhabarbarum. The leaves of R. palmatum are deeply palmately divided, while those of R. rhabarbarum are triangular-ovate to ovate with entire or sinuate-dentate margins, and the species is selected for edible petioles rather than the medicinal roots of R. palmatum; notably, leaves of both are toxic and non-edible. R. rhabarbarum also bears white or greenish-white flowers, unlike the purple-red of R. palmatum. Identification of R. palmatum relies on key traits including leaf shape, flower color, and root structure:

Habitat and distribution

Native range

_Rheum palmatum is native to the mountainous regions of western and northern , including provinces such as , , , , , and , as well as northern (Xizang) and the . Its natural distribution extends into north and , with some records indicating presence in . In its native , the occurs at elevations ranging from 1,500 to 4,400 meters in and subalpine zones, primarily on slopes, valleys, and rocky areas. Distribution maps from botanical databases illustrate its concentration in the temperate biomes of these high-altitude regions, highlighting a patchy but widespread occurrence tied to specific topographic features. The plant has been introduced and cultivated beyond its native range for medicinal and ornamental purposes, including in (such as ) since the 18th century, , and other parts of . This spread occurred historically along trade routes like the , where its roots were valued in and transported to distant markets.

Habitat preferences

_Rheum palmatum is adapted to high-altitude environments in mountainous regions, where it occurs on scrub-covered rocky slopes and along stream banks at elevations typically ranging from 2500 to 4000 meters. These habitats provide the moist, well-drained conditions essential for its growth, preventing while supporting nutrient uptake in nutrient-rich substrates. The species favors cool temperate climates with full sun exposure, enabling robust vegetative development during short growing seasons. It demonstrates strong cold tolerance, surviving winter temperatures as low as -20°C, which aligns with the harsh conditions of its native alpine and subalpine zones in the and . Soil preferences center on fertile, humus-rich loams or heavy clay types that retain moisture without becoming waterlogged, with optimal levels ranging from to slightly acidic (approximately 6.0–7.0). Such soils, often found in valley slopes and edges, facilitate the plant's deep , which anchors it against and accesses subterranean water in these rugged terrains.

Ecology

Reproduction

Rheum palmatum is a monoecious , producing both male and female reproductive organs within the same flowers, which are small and pinkish, arranged in large panicles up to 1 meter tall. These flowers bloom during summer, typically from to in its native range, with seed set occurring in autumn from July to September. is primarily facilitated by , as the species is anthophilous and self-incompatible, promoting outcrossing to enhance ; common pollinators likely include bees and flies attracted to the flowers' and . Following pollination, the plant develops trigonous achenes as fruits, which are winged to aid in dispersal primarily by wind, though gravity also plays a role in local spread. Seed viability remains high for several weeks post-maturity, with germination rates typically exceeding 60% under optimal conditions, such as storage at 25°C for up to eight weeks and sowing in moist, well-drained soil; rates can reach up to 98% for fresh seeds when soaked for 24 hours prior to planting. Germination usually occurs within 13 days at temperatures around 20–25°C, contributing to the plant's ability to establish in suitable habitats. In addition to , R. palmatum propagates asexually through division or root cuttings, a method that maintains clonal uniformity and is commonly used in . As a rhizomatous , it exhibits a growth cycle where new shoots emerge from the underground rhizomes each spring. This asexual strategy supports the plant's persistence in stable environments, complementing seed-based dispersal for colonization.

Ecological interactions

Rheum palmatum attracts a variety of insect visitors to its pinkish flowers, thereby supporting pollinator diversity in its native alpine meadow habitats. These interactions enhance biodiversity by providing nectar and pollen resources during the flowering period from June to July. The plant exhibits defenses against herbivory through high concentrations of oxalic acid in its leaves, rendering them toxic and unpalatable to livestock and potentially deterring insect herbivores. Its robust underground root system offers additional protection, allowing the perennial to persist in rocky, disturbed environments where above-ground foliage may be vulnerable. Furthermore, the species shows resistance to rabbit browsing, acting as a reliable companion plant in mixed ecosystems. In its native rocky slopes and streamside habitats, R. palmatum contributes to via its extensive rhizomatous root network, which anchors and mitigates in sloped, moist terrains. Wild populations face significant threats from overharvesting for medicinal purposes, contributing to their endangered status and reduced in remnant habitats. In introduced regions, such as parts of and , the plant can self-seed and spread modestly, though it is not widely regarded as invasive.

History

Traditional use in Asia

Rheum palmatum, known as dahuang in (TCM), has been utilized for over 2,000 years primarily for its purgative properties, as well as to address fever and digestive disorders such as and . In TCM, it is classified as a cooling that clears heat, invigorates blood, and promotes bowel movements, often prescribed in formulas to treat conditions involving excess heat or stagnation in the body. Its earliest documented use appears in the Shennong Bencao Jing, a foundational compiled between the 1st and 2nd centuries AD, where it is described as bitter and cold, suitable for expelling toxins and relieving fire-related ailments. The preparation of Rheum palmatum in traditional Asian practices typically involves harvesting the roots and rhizomes in autumn from plants at least three years old, followed by cleaning, slicing, and sun-drying to preserve potency. These dried materials are then commonly decocted in water to create herbal teas or added to multi-ingredient formulas, with processing methods like stir-frying or steaming sometimes applied to modulate its effects, such as reducing its strong purgative action for gentler use. Ancient texts like the Shennong Bencao Jing emphasize careful harvesting to avoid depleting vital energy from the plant, ensuring sustainable use in medicinal preparations. Trade in Rheum palmatum roots along the began in the 14th century CE, facilitating its export from to the and eventually as a valued medicinal . This exchange highlighted its reputation as a versatile remedy, with dried roots bundled and transported over long distances, often commanding high prices due to their perceived efficacy against digestive and febrile conditions. Beyond , Rheum palmatum features prominently in Tibetan medicine, where it is employed to treat , , and blood disorders, often combined with other herbs to balance its cooling effects. In Mongolian folk medicine, it serves similar roles, acting as a key ingredient in formulations like Liuwei'an Xiaosan for alleviating and abdominal issues, reflecting shared therapeutic traditions across Central Asian cultures. These applications underscore its enduring role in regional healing practices, though primarily medicinal rather than ritualistic or dietary.

Introduction to the West

Rheum palmatum, commonly known as Chinese rhubarb or Turkey rhubarb, was formally named by the Swedish botanist in his (10th edition, 1759), based on dried specimens imported from . This taxonomic designation marked the plant's entry into Western scientific , distinguishing it from other rhubarb and facilitating its study in European botanical circles. Native to the mountainous regions of , , and , the plant's roots had long been valued in Eastern , but its introduction to the West began with these early specimens. The first successful cultivation of R. palmatum in occurred in around 1762, when seeds imported from were sown in botanical gardens, including those in by 1764. This development was driven by efforts to produce the medicinal root locally, reducing reliance on expensive imports and ensuring supply for apothecaries. By the late , British physicians like William Fordyce advocated for expanded cultivation, publishing methods in 1792 to promote its growth for therapeutic purposes. Meanwhile, trade in the dried root, known as "Turkey rhubarb," flourished through intermediaries, with overland routes from via the supplying European markets during the 18th and 19th centuries; prices could rival those of luxury spices due to its and . In early Western applications, R. palmatum roots were primarily employed as a potent in apothecary medicine, valued for treating and digestive disorders without the harsh effects of other purgatives. Botanical interest grew through studies by explorers and naturalists, contributing to its integration into pharmacopeias. Additionally, yielded yellow-orange dyes, used in coloring, though less prominently than its medicinal role. By the , the plant gained popularity as an ornamental in gardens for its dramatic palmate leaves and tall flower spikes, leading to the of cultivars such as 'Atrosanguineum' with deep red foliage, enhancing its appeal in .

Phytochemistry

Active compounds

The primary active compounds in Rheum palmatum are anthraquinones, which constitute a major class of metabolites responsible for many of its biochemical properties. Key anthraquinones include , , aloe-emodin, chrysophanol, and physcion, with total concentrations ranging from 3% to 5% in the dried roots. These compounds occur predominantly in free and glycosylated forms, contributing to the plant's characteristic pigmentation and profiles. In addition to anthraquinones, R. palmatum contains other significant chemical classes such as stilbenes, including rhaponticin, rhapontigenin, and isorhapontigenin; tannins, which are hydrolyzable and condensed types comprising 10% to 30% of the root material; polysaccharides; flavonoids; and anthrones like rheinosides A–D and sennosides A–F. Stilbenes and flavonoids are present in lower abundances compared to anthraquinones and tannins, while polysaccharides form complex carbohydrate structures that enhance the plant's overall extractability. Anthrones serve as biosynthetic precursors to anthraquinones, often accumulating alongside them. The highest concentrations of these active compounds are found in the roots and rhizomes, where and predominate, with levels varying based on plant age—typically increasing after 3–5 years of growth—and processing methods such as drying or steaming, which can alter and total yields. For instance, older roots exhibit elevated content due to prolonged . Extraction of these compounds has evolved from historical techniques, such as water or alcohol maceration used in traditional preparations to yield crude tinctures, to modern analytical methods like (HPLC), which enables precise quantification and isolation of individual and stilbenes with high purity. HPLC, often coupled with UV detection, has become standard for , allowing separation of compounds like and in root extracts within minutes.

Pharmacological basis

The pharmacological basis of Rheum palmatum centers on its derivatives, such as and , which underpin its primary therapeutic effects. These compounds are metabolized by colonic bacteria into active anthrones that inhibit Na⁺/K⁺-ATPase in intestinal epithelial cells, promoting chloride ion secretion and subsequent accumulation of water and electrolytes in the lumen. This osmotic effect, combined with stimulation of the and contraction, enhances and facilitates , establishing the plant's action. Anti-inflammatory effects arise mainly from emodin, which suppresses the pathway by preventing IκBα degradation and inhibiting p65 nuclear translocation, thereby reducing production of pro-inflammatory mediators like TNF-α, IL-6, and MMPs in activated macrophages and synovial cells. Stilbenes, such as rhaponticin present in the plant, contribute properties by scavenging (ROS) and inhibiting enzymes like COX and LOX, mitigating and inflammation. Beyond these, R. palmatum exhibits antimicrobial activity, particularly against , where disrupts bacterial cell membrane integrity, inhibits formation, and attenuates virulence factors like and at sub-MIC concentrations (e.g., 6.25–12.5 µg/mL). In anticancer contexts, induces in various tumor cells, including lines, via ROS generation, activation of , and modulation of and pathways, leading to arrest and mitochondrial dysfunction. Bioavailability of key anthraquinones is limited, with poor in the upper and primary activation occurring via microbial reduction in the colon; systemic exposure is further influenced by hepatic through UDP-glucuronosyltransferase (UGT) enzymes like UGT2B7. This profile raises concerns for drug interactions, as R. palmatum activates efflux pumps and modulates transporters, reducing the of substrates such as by up to 52% in pharmacokinetic studies.

Cultivation

Ornamental cultivation

Rheum palmatum is valued in ornamental for its dramatic, large palmate leaves and towering flower stalks, which add architectural interest to gardens. It performs best in full sun to partial , preferring fertile, evenly moist but well-drained soils rich in . The plant is in USDA zones 5–7, enduring winter temperatures as low as -20°C, though it benefits from protection in exposed sites. In hotter climates, afternoon helps prevent leaf scorch. Propagation of Rheum palmatum for garden use typically occurs through seed sowing or root division. Seeds require cold stratification for 1–2 months at around 2–4°C to break dormancy before spring sowing, achieving higher germination rates when fresh and treated with gibberellic acid. Division is preferred for true-to-type plants and is carried out in early spring, separating the rhizomatous crowns into sections each with at least one bud. Plants should be spaced 1–1.5 meters apart to accommodate their mature spread of up to 1.8 meters. Popular cultivars enhance the ornamental appeal with varied foliage colors and forms. 'Bowles's Crimson' displays striking red foliage in spring that matures to green with red undersides, providing bold contrast in borders. 'Hadspen Crimson', which holds the Royal Horticultural Society's Award of Garden Merit, produces large, incised leaves that emerge deep crimson before turning green, adding vibrant color through the season. Maintenance involves mulching annually with organic material to retain and keep roots cool, especially in summer. Division every 5–7 years rejuvenates clumps, preventing overcrowding and maintaining vigor, and can be done in or after flowering. The bold foliage offers year-round structure, emerging reddish in and forming expansive rosettes that pair well with perennials in or gardens.

Medicinal production

Rheum palmatum is commercially cultivated primarily for the of bioactive compounds from its and , with planting typically achieved through rhizome cuttings or . The crop follows a long cycle, requiring 6–10 years of growth before harvest to allow sufficient accumulation of medicinal constituents in the underground parts. Harvesting occurs in autumn, generally between and in major areas, or sometimes in May, when the rhizomes are dug up from mature . Optimal growth demands fertile, deep loamy soils that are humus-rich, moisture-retentive, and well-drained, often in heavy clay or loamy conditions with good content. The plant thrives in cool, climates at altitudes of 2500–4400 meters in scrub or environments, exhibiting hardiness down to around -20°C and for full sun or semi-shade. Primary production regions include highland areas of , particularly Province, the main production area, alongside ; minor cultivation occurs in , , , and the for export purposes. Post-harvest processing begins with thorough cleaning of the and rhizomes to remove and outer , followed by peeling, slicing into thin pieces, and sun-drying or oven-drying to preserve quality and bioactive components. The dried material is then cut into small pieces or powdered for and pharmaceutical , ensuring minimal loss of heat-sensitive compounds. Processed typically yield 1.5–3.4% total anthraquinones by weight, depending on variation and environmental factors, with as a dominant . Yields average 8–12 kg of dried rhizomes per plant in systems. To address overharvesting of wild populations and prevent nutrient depletion, sustainable practices emphasize in planting bases, integration of biofertilizers like species, and amendments such as to enhance growth and nutrient uptake while reducing reliance on chemical inputs. These approaches support long-term in intensive production areas, where global output remains dominated by without precise aggregate tonnage estimates available.

Medicinal uses

Traditional applications

In Traditional Chinese Medicine (TCM), Rheum palmatum, known as Da Huang, has been employed primarily as a purgative to relieve by promoting bowel movements and purging accumulations in the intestines. It is also utilized to reduce fever by clearing internal heat and to detoxify the blood, addressing conditions involving , , and . Typical dosages range from 3–12 g of dried root per day, adjusted based on the condition and preparation method. The is commonly prepared as decoctions by 3–12 g of dried slices in water for 10–15 minutes, powders by mixing 1–2 g in warm water or capsules, or incorporated into pills and formulas for internal use. It is frequently combined with other , such as licorice (Gan Cao), to harmonize effects, prevent abdominal cramps, and protect the during purgative treatments. In other traditional systems, such as , R. palmatum is applied for ailments, including as made from ground root mixed with vinegar to treat eczema, , boils, and wounds by reducing and promoting healing. Externally, it has been used as a for swelling and fever-related issues. Culturally, R. palmatum holds significant place in ancient TCM texts like the Shen Nong Ben Cao Jing (circa 270 BC), where it is classified as a superior for heat-clearing to restore yin-yang balance and eliminate pathogenic heat from the body.

Modern research

Modern research on Rheum palmatum has focused on validating its traditional uses through clinical and preclinical studies, particularly emphasizing its and properties. A double-blind, randomized, -controlled involving middle-aged adults with chronic demonstrated that supplementation with rhubarb extract significantly increased stool frequency and improved gut composition by promoting butyrate-producing and short-chain fatty acid production, confirming its efficacy. Another randomized evaluated a herbal capsule containing free anthraquinones from rhubarb, showing superior stool-softening effects compared to in postoperative patients, with no significant adverse events reported. Studies on anti-inflammatory applications have highlighted the role of anthraquinones like and . A 2022 investigation using and T-cell models of found that R. palmatum extract, particularly and , suppressed pro-inflammatory cytokines such as TNF-α, IL-17, CXCL8, and , reducing keratinocyte hyperproliferation and suggesting potential for psoriasis treatment. Emerging research explores broader therapeutic potentials. In anticancer studies, induced in cell lines (HT-29 and SW480) via activation and mitochondrial pathways, while promoted cell cycle arrest and in breast and tongue squamous cancer cells. For antidiabetic effects, improved insulin sensitivity and glucose uptake in animal models, with a 2023 review summarizing its inhibition of α-glucosidase and enhancement of translocation over the past decade. Antimicrobial investigations indicate and inhibit SARS-CoV-2 main protease and block spike protein-ACE2 interactions, as shown in molecular docking and assays from 2021–2022 studies. The European Medicines Agency's 2020 herbal monograph recognizes R. palmatum root for short-term relief of occasional , based on well-established use, but cautions against prolonged administration due to risks of intestinal dependence. Research gaps persist in long-term safety, with calls for extended human trials to assess chronic effects beyond use. Publications from 2017 to 2025 have advanced understanding of , revealing low oral absorption of anthraquinones like and due to rapid metabolism and transformation, prompting development of standardized extracts to enhance efficacy. For instance, nano-formulated extracts improved bioavailability in pharmacokinetic models, supporting optimized medicinal production.

Safety and risks

Toxicity

The leaves of Rheum palmatum contain high concentrations of , which can bind to calcium and form insoluble crystals that damage the kidneys upon ingestion, potentially leading to acute renal failure. Historical cases of , including goats and swine, have been reported from consumption of rhubarb leaves, resulting in symptoms such as weakness, tremors, and bloody urine due to toxicity. The roots of R. palmatum harbor anthraquinones such as and , which become toxic in excess and can disrupt electrolyte balance, particularly by causing through severe . Overconsumption may induce acute symptoms including , , griping , and profuse . Toxicity estimates for key anthraquinones include an intraperitoneal LD<sub>50</sub> of approximately 35 mg/kg body weight for in mice, indicating moderate acute potency via non-oral routes.

Contraindications

_Rheum palmatum is contraindicated during due to its constituents, such as , which act as uterine stimulants and increase the risk of ; this applies to all trimesters based on preclinical data indicating genotoxic potential and traditional Chinese medicine observations of effects. Use with caution in individuals with due to the plant's high content and potential for ; while it may exacerbate renal damage and lead to acute renal failure with prolonged exposure or overuse, is sometimes used therapeutically in CKD under medical supervision. Similarly, it is contraindicated in cases of intestinal obstruction, as the properties may worsen the condition, and caution is advised for or due to potential aggravation of inflammatory joint issues. Long-term use of Rheum palmatum has been associated with liver , imbalances, and , stemming from chronic exposure that promotes organ enlargement and renal protein leakage. Interactions with diuretics or heart medications, including cardiac glycosides, are a concern because the effect of Rheum palmatum can cause depletion, amplifying and increasing the toxicity of these drugs. Due to overharvesting pressures on wild populations in native regions like and , sustainable sourcing from cultivated stocks is recommended to mitigate conservation threats to Rheum palmatum.

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