Pokeweed

Pokeweed (Phytolacca americana L.): A Comprehensive Reference

1. Identity and Botanical Description

Nomenclature and Taxonomy

Pokeweed (Phytolacca americana L., synonym P. decandra L.) — also known as American pokeweed, poke sallet, pokeberry, dragonberries, pigeonberry weed, and inkberry — is a poisonous, herbaceous perennial plant in the pokeweed family Phytolaccaceae. The genus Phytolacca is large and globally distributed; it has 25–35 species worldwide, including four species in the People's Republic of China. The name "poke" derives from indigenous North American languages: its namesake is derived from the Algonquian word "pocan," a term given to plants producing red dye.

Morphology and Distribution

Pokeweed grows 1 to 3 metres (4 to 10 ft). It has simple leaves on green to red or purplish stems and a large white taproot. The flowers are green to white, followed by berries which ripen through red to purple to almost black. Pokeweed is native to eastern North America, the Midwest, and the South, with more scattered populations in the far West where it was introduced. It is also naturalized in parts of Europe and Asia. It grows in open or edge habitats, forest edges, in fence rows, pastures, old fields, and forest openings.

Pharmacopeial and Regulatory Status

Phytolacca americana (Phytolaccaceae), in addition to serving as an occasional food, is a medicinal plant listed officially in the United States and in the French and Japanese Pharmacopeia.

Common Preparations and Forms

The different plant parts are each associated with distinct preparations. The root (poke root or radix Phytolaccae) has historically been the primary medicinal part, used as a dried root, tincture, or decoction. The young spring leaves have been processed for food. The berries have been used to produce dye and, after seed removal, as a juice. The plant and its tissue cultures have been investigated as a source of saponins, betalains, mitogens, and antiviral proteins. In contemporary practice, pokeweed is available commercially as tinctures, dried root powder, homeopathic dilutions, and — in a research context — as isolated protein fractions such as pokeweed antiviral protein (PAP) and pokeweed mitogen (PWM).

2. Traditional and Historical Use

Indigenous North American Use

Poke has been a prominent food source and medicine to indigenous Americans since long before the arrival of even the earliest Appalachian settlers. The plant has a history of being used as food, medicine, and a coloring by indigenous people long before others ate it. Various tribal nations made distinct medicinal use of the plant: the Cherokee used it to address rheumatism and joint complaints, and the plant was widely considered a medicine rather than a simple food by most peoples.

Appalachian and Southern United States Food Tradition

A darling of Appalachian culture, pokeweed is often referred to as "poke sallet" (commonly misspelled "poke salad") in reference to the traditional dish prepared with young poke leaves and shoots, boiled, drained, then cooked with salt and bacon grease. Cooking it this way, by boiling only the meristematic shoots and tips and discarding the water, ensures its safe consumption. It was, and for many still is, as much a staple of the Appalachian diet as collards or hoe cakes. It was a staple dish in rural and impoverished communities during the spring season when other fresh produce was scarce.

Poke salad ("poke salat") is considered part of traditional southern U.S. cuisine, where it is cooked three times in three changes of boiling water to remove some of the harmful components. Only the young, tender shoots — harvested before the plant flowers — should be used for cooking.

Folk Medicine in Europe and Korea

The plant has been used in folk medicine as a diuretic, purgative, antiscorbutic, and antisyphilitic agent. The roots are reputed in Korea to treat edema and rheumatism. At present, P. americana is used in some French homeopathic preparations to alleviate influenza, acute amygdalitis, quinsy, mammary and rheumatic pains, and chronic pharyngitis.

Traditional Use in Asian Medicine

The plant has a long history of usage in traditional medicine for treating a variety of ailments including infectious diseases, edema, inflammation, gastric, and abdominal distress. In both Asian and Western traditional medicine, plants from the Phytolaccaceae family are frequently used to treat inflammation, edema, dermatitis, tumors, rheumatism, bronchitis, and as molluscicides. A third Phytolacca species with white flowers is also used: P. americana Linnaeus (American pokeweed, synonym P. decandra), regularly cited for its traditional use to treat edema, ascites, and skin infections.

19th-Century Western Herbal and Pharmaceutical History

The late 19th century herbal, the King's American Dispensatory, describes various folk medical uses that led individuals to ingest pokeberry products. Phytolacca extract was advertised as a prescription weight loss drug in the 1890s. In traditional Western herbalism, poke root has long been categorized as having lymphatic, alterative, and anti-catarrhal actions. Poke root is described as a slow-acting emetic, a purgative, and a mild narcotic that has a long history of use in herbal medicine for a number of chronic health conditions.

Dye Use

The berries are poisonous to humans but have been used to make dye and are a favored food of migrating songbirds. Historically, the dark berry juice was used by American colonists to dye cloth and as an ink substitute.

3. Phytochemistry: Key Constituents and Classes

Triterpene Saponins

Triterpene-containing saponins account for the majority of the chemical components in these plants, along with flavonoids, triterpenes, phenolic acids, polysaccharides, and sterols. Several bioactive natural products have been identified from Phytolacca, including glycosylated saponins such as esculentosides and phytolaccosides, as well as a few flavones (cochliophilin A) and phytosterols (α-spinasterol), which contribute to Phytolacca's anti-inflammatory and/or anticancer effects. Specifically, the root saponin fraction includes phytolaccosides A-1, D2, and O, with aglycones such as phytolaccagenin, jaligonic acid, phytolaccagenic acid, aesculentic acid, and acinosolic acid methyl ester.

Lectins / Pokeweed Mitogen (PWM)

Lectins in pokeweed consist of pokeweed mitogen (PWM), a mixture of five glycoproteins designated Pa-1 to Pa-5. Pokeweed mitogen is a mitogen derived from the roots of Phytolacca americana. It functions as a lectin and a mitotic stimulus for the division of lymphocytes. This lectin specifically induces the proliferation of B cells, plasma cells, and T cells.

Pokeweed Antiviral Protein (PAP)

Pokeweed antiviral protein (PAP) from Phytolacca americana is a ribosome-inactivating protein (RIP) and is an RNA N-glycosidase that removes specific purine residues from the sarcin/ricin (S/R) loop of large rRNA, arresting protein synthesis at the translocation step. PAP is thought to play an important role in the plant's defense mechanism against foreign pathogens. PAP occurs in multiple isoforms: PAP-I (spring leaves), PAP-II (summer leaves), and PAP-S (seeds), each with slightly different expression patterns but similar enzymatic activity.

Alkaloids

Toxic constituents which have been identified include the alkaloids phytolaccine and phytolaccotoxin, as well as a glycoprotein.

Phenolic Compounds and Flavonoids

The phenolic compounds found in the pokeweed berry extract belong to the following groups: flavonoids (rutin, quercetin, catechin, epicatechin) and phenolic acids (gallic acid, ferulic acid, ellagic acid, chlorogenic acid, 2,4-dihydroxybenzoic acid).

Neolignans

Other constituents include isoamericanin A (a neolignan), pokeweed antiviral protein, α-spinasterol, histamine, and GABA. Seed derivative americanin A shows antitumor activity for human colon cancer, while isoamericanin B and C inhibit tyrosinase activity.

Other Constituents

Active plant constituents include triterpene saponins, a tannin, a resin, and a protein called pokeweed mitogen. Pokeweed's histamine and GABA content may have hypotensive effects.

Distribution of Constituents Across Plant Parts

Toxic components are highest in the rootstock, less in the mature leaves and stems, and least in the fruit. The roots have been described as widely toxic due to a high content of mitogen (a single-chain protein capable of inhibiting ribosomal RNA) and saponins.

4. Mechanisms of Action

Ribosome Inactivation by PAP

PAP is an RNA N-glycosidase that removes specific purine residues from the sarcin/ricin (S/R) loop of large rRNA, arresting protein synthesis at the translocation step. Like all ribosome-inactivating proteins, PAP is an N-glycosidase that cleaves an adenine from the conserved sarcin/ricin loop of the large subunit ribosomal RNA. Depurinated ribosomes are unable to bind elongation factor 2, resulting in inhibition of translation and subsequent cell death.

A model for PAP's in vivo antiviral mechanism proposes that PAP (a cell-wall protein) selectively enters virus-infected cells and disrupts protein synthesis, thus causing local suicide and preventing virus replication. PAP and nontoxic mutants of PAP can directly depurinate brome mosaic virus (BMV) RNA in vitro, resulting in reduced viral protein translation.

Direct Viral RNA Depurination

Studies have demonstrated that PAP also depurinates other RNA templates, such as Human Immunodeficiency Virus-1 (HIV-1) RNA and Brome Mosaic Virus RNAs. Pokeweed antiviral proteins PAP-I, PAP-II, and PAP-III cause a concentration-dependent depurination of genomic HIV-1 RNA, TMV RNA, poliovirus, herpes simplex virus, influenza virus, and brome mosaic virus RNA.

Interaction with Translation Initiation Factors

Considering that PAP was shown to bind the m7G of the cap structure of mRNA, PAP may interact with other factors involved in translation initiation. By far-western analysis, PAP binds specifically to eIF4G and eIFiso4G, and a region of eIFiso4G between amino acids 511 and 624 is required for PAP binding activity. The mode of action for the antiviral activity of RIPs is poorly understood; however, this activity does not depend solely on ribosomal inactivation. An alternative mechanism may involve a direct interaction of RIP with viral RNA or DNA, with additional effects brought about by eukaryotic translation initiation factors (eIFs).

Immunostimulatory Mechanism of PWM

Highly purified PWM preparations have been found to fail to induce B cell proliferation. By contrast, commercially available PWM preparations with B cell activity contained Toll-like receptor (TLR) ligands such as TLR2-active lipoproteins, lipopolysaccharide, and DNA of bacterial origin, and these microbial substances contribute to the stimulatory activity of PWM. This finding importantly revised earlier assumptions about PWM's intrinsic immunostimulatory mechanism.

Anti-Inflammatory Mechanisms of Saponins

Saponin extracts, chiefly phytolaccagenin, exhibit anti-inflammatory activity as demonstrated by carrageenan rat paw edema tests. Several bioactive natural products identified from Phytolacca, including glycosylated saponins such as esculentosides and phytolaccosides, as well as cochliophilin A and α-spinasterol, contribute to Phytolacca's anti-inflammatory and/or anticancer effects.

5. Scientific Evidence by Area of Application

5.1 Antiviral Activity

Evidence type: Predominantly in vitro and animal studies; no completed human clinical trials on PAP as a standalone antiviral agent.

Pokeweed antiviral protein (PAP) is a ribosome-inactivating protein isolated from Phytolacca americana that inhibits the proliferation of several plant and animal viruses. Pokeweed antiviral protein shows broad antiviral activity in vitro, and inhibits replication of herpes simplex, influenza, and poliovirus, possibly via inactivation of eukaryotic ribosomes.

PAP is a naturally occurring broad-spectrum antiviral agent with potent anti-human immunodeficiency virus (HIV)-1 activity, the molecular mechanism of which remains an area of ongoing investigation. Lab studies suggest pokeweed extracts may stop the growth of certain fungi and viruses, but human data are lacking.

5.2 Immunotoxin / Cancer Therapy Research

Evidence type: Preclinical animal studies and Phase I/II clinical trials; no approved therapeutic product.

PAP from the leaves of pokeweed is a naturally occurring single-chain ribosome-inactivating protein, which catalytically inactivates both prokaryotic and eukaryotic ribosomes. The therapeutic potential of PAP has gained considerable interest in recent years due to the clinical use of native PAP as the active moiety of immunoconjugates against cancer and AIDS.

A standardized method was developed for the preparation and purification of a potent immunotoxin against B-lineage leukemia/lymphoma cells, constructed with the ribosome inhibitory single-chain plant toxin PAP and a murine IgG1 monoclonal antibody specific for the human B lineage differentiation antigen CD19, for human clinical trials. PAP has been used as the ribosomal-inhibitory (cytotoxic) moiety of an anti-CD19 immunotoxin in Phase I/II clinical trials of adult and pediatric patients with acute lymphoblastic leukemia under an Investigational New Drug Application (BB-IND-3864) approved by the Food and Drug Administration.

In preclinical cynomolgus monkey studies, B43-PAP was very well tolerated, with no significant clinical or laboratory signs of toxicity at total dose levels ranging from 0.007 to 0.7 mg/kg. A transient episode of mild capillary leak was observed at total dose levels equal to or higher than 0.35 mg/kg. At total dose levels of 3.5 and 7.0 mg/kg, B43-PAP caused dose-limiting renal toxicity due to severe renal tubular necrosis.

In vitro and earlier test-tube studies demonstrate that, when extracted from the plant, some bioactive compounds may have anticancer effects: esculentoside A may inhibit breast cancer growth, while esculentoside H may prevent human cancer cells from migrating. Additionally, compounds isolated from pokeweed seeds, americanin A and isoamericanol A, may have anticancer effects on colon and breast cancer. These findings remain preliminary and have not been validated in human trials.

5.3 Immunological Research Tool (Pokeweed Mitogen)

Evidence type: Well-established use as a laboratory research and diagnostic tool; not a therapeutic application per se.

PHA, Con A, and pokeweed mitogen activation are commonly used in clinical labs to assess patients' immunity and to assess the effectiveness of numerous immunosuppressive and immunotherapeutic treatments. PWM is commonly used for B cell assays in vitro. Along with "SAC" (formalin-fixed S. aureus cells), it is the most frequently used stimulatory reagent in assays performed for diagnostic purposes, such as evaluating B cell function in patients with suspected immunodeficiency.

5.4 Anti-Inflammatory Activity

Evidence type: Animal and in vitro studies only; no clinical trials in humans.

Different types of Phytolacca extracts show a range of pharmacological activities including antioxidant, anti-inflammatory, anti-parasitic, antifungal, anticancer, and insecticidal effects. The marked anti-inflammatory activity of Phytolacca extracts supports its use in treating diseases such as arthritis, nephritis, and rheumatism, as well as in combating cancer. However, these conclusions are drawn from animal and in vitro studies. Although pokeweed extracts reduced inflammation in an animal study, clinical trials are lacking. The saponins showed anti-inflammatory activity in a rat paw edema model at doses 10-fold lower than the LD50; however, the toxicity of the saponins precludes their use in inflammation.

5.5 Antifungal Activity

Evidence type: In vitro only.

An antifungal peptide extract from pokeweed displayed fungistatic effects against a variety of species in vitro. No human studies have evaluated this application.

5.6 Other Investigated Activities

Poke extracts were found to have inhibitory activity in a model of diabetic nephropathy. The sterol alpha-spinasterol was isolated as the active principle. Some of the neolignans of poke promote neurite outgrowth in rat cortical neuron cultures. Antiproliferative and antitumor activities have been described for the component americanin A, as well as acetylcholinesterase inhibitory activity from the leaf extract. All of these findings are at the in vitro or animal-model stage, and none have been validated in human trials.

5.7 Overall Assessment of Human Clinical Evidence

While pokeweed has been subject to laboratory research, there is no medical evidence that it has any beneficial effect on human health. The only human clinical application of a pokeweed-derived compound involves PAP used as the toxic moiety within experimental immunotoxin conjugates (e.g., B43-PAP) for hematological malignancies — a highly engineered pharmaceutical context distinct from any supplement or herbal preparation.

6. Body Systems and Health Areas Associated with Pokeweed

Lymphatic System

Poke root has a specific action on the lymphatic system and is used traditionally to increase lymphatic drainage. It is most indicated in cases of hard lymph nodes with pale congested mucous membranes.

Immune System

PWM has been extensively used as a laboratory tool to study B and T lymphocyte activation and differentiation. Due to their potent immunostimulatory properties, Phytolacca americana extracts are used in patients with infections and cancer in some traditional medicine contexts, though clinical evidence for efficacy is absent.

Musculoskeletal System

Saponin contents accumulated in the roots have pharmaceutical uses explored in the context of rheumatism treatments and anti-inflammation. Traditional use for rheumatism and joint complaints is historically documented across multiple cultures, but no controlled human trials validate this use.

Respiratory System

In Western herbal tradition, poke root has been used as an expectorant and anti-catarrhal agent for bronchitis and chronic catarrh. The plant has been used in folk medicine as a diuretic, purgative, antiscorbutic, and antisyphilitic agent. These uses reflect historical categorizations without modern clinical evidence.

Skin and Mucosal Tissues

All plant parts are irritating to the mucosal membranes and toxic due to saponins and lectin content. Despite this, topical preparations have been historically described for treating skin infections and wounds.

Cardiovascular System

In one reported case, Mobitz type I heart block was associated with vomiting due to pokeweed, which resolved after intravenous promethazine. The authors suggested that the heart block had been due to increased vagal tone associated with severe gastrointestinal colic.

7. Dosage Forms and Dosages Reported in Sources

There are no established safe or therapeutic dosages for pokeweed preparations in humans. The following reflect what has been reported in various sources and should be understood in that context only.

• Pokeroot tea (reported exposure): Severe poisonings have been reported in adult humans who ingested mature pokeweed leaves and as little as 1 cup of tea brewed with ½ tsp of powdered pokeroot.
• Preclinical immunotoxin (B43-PAP, in cynomolgus monkeys): B43-PAP was very well tolerated with no significant clinical or laboratory signs of toxicity at total dose levels ranging from 0.007 to 0.7 mg/kg.
• Saponin anti-inflammatory dose (rat paw edema model): The saponins showed anti-inflammatory activity in a rat paw edema model at doses 10-fold lower than the LD50; however, the toxicity of the saponins precludes their use in inflammation.
• French homeopathic preparations: At present, P. americana is used in some French homeopathic preparations to alleviate influenza, acute amygdalitis, quinsy, mammary and rheumatic pains, and chronic pharyngitis. Homeopathic dilutions are prepared at highly attenuated concentrations per classical homeopathic practice.

8. Safety Considerations and Toxicology

General Toxicity

Pokeweed is poisonous to humans, dogs, and livestock. All parts of the plant are toxic, except the above-ground leaves that grow in the early spring, which can be eaten after proper preparation. Toxic components are highest in the rootstock, less in the mature leaves and stems, and least in the fruit. Ingestion of poisonous plant parts causes severe stomach cramping, nausea, emesis, persistent diarrhea, dyspnea, weakness, spasms, hypotension, seizures, and death.

Specific Toxic Agents

American pokeweed contains toxic substances such as saponins and oxalates, which have led to multiple poisoning incidents in recent years. All plant parts are irritating to the mucosal membranes and toxic due to saponins and lectin content. Toxicity is reduced through boiling, as lectins are destroyed by heat.

Symptoms of Poisoning

Symptoms of poisoning include vomiting, diarrhoea (bloody), strong thirst, dizziness, somnolence, drop in blood pressure, and tachycardia, leading to seizures and death due to respiratory depression. Inhaling the dried root can lead to sneezing fits due to saponin content.

Epidemiology of Poisoning Cases

A retrospective observational study of pokeweed exposures in Kentucky (2000–2019) drawn from the National Poison Data System found that: the majority of patients were male (54.9%), with unintentional exposures representing most exposure reasons (97.2%). Oral ingestion of plant material represented the bulk of the exposure route (98.3%), with pokeberries most often implicated in these cases (93.9%). Abdominal pain, nausea, vomiting, and diarrhea were most common. Dermal exposures resulted in cutaneous edema, pain, and swelling. Treatments were mainly supportive, with no deaths reported during the study timeframe. A fatal case of acute pokeweed leaf poisoning has been documented in China, where American pokeweed has become widely distributed in both rural and urban areas, and where its toxic substances have led to multiple poisoning incidents.

Heat Processing and Toxin Reduction

Toxicity is reduced through boiling, as lectins are destroyed by heat. Young plant parts can be eaten only after proper preparation: they must be boiled two or more times, with the water drained and replaced between each boil. The root is never eaten and cannot be made edible.

Dermal Exposure

Skin contact with plant sap, particularly from broken stems or roots, can result in local irritation and edema. Dermal exposures resulted in cutaneous edema, pain, and swelling. The toxins can be absorbed transdermally, particularly through cuts or abraded skin.

Interactions

Pokeweed's histamine and GABA content may have hypotensive effects, suggesting a potential for additive effects with antihypertensive medications, though this has not been formally studied in clinical pharmacokinetic trials. Based on its known pharmacologically active constituents, particular caution is warranted with concurrent use of immunosuppressants (given the immunostimulatory lectin content), anticoagulants (given documented gastrointestinal hemorrhage risk from saponins), and antihypertensive agents.

Special Populations

Pokeweed should never be used by pregnant women. Given its documented severe systemic toxicity, including emetic, hypotensive, and potentially fatal effects at uncharacterized doses, it presents an unacceptably high risk in vulnerable populations including children and pregnant or nursing individuals.

Regulatory and Clinical Standing

There is unlikely to be a valid medical indication for the use of this plant as an herbal preparation, according to toxicological assessments. While pokeweed has been studied in laboratory settings, there is no medical evidence that it provides any beneficial health effects for humans. The plant's most scientifically advanced application — as the toxic payload in PAP-based immunotoxins — is exclusively a pharmaceutical research context, not a dietary supplement or herbal medicine context.

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