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Lobelia
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Lobelia
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Lobelia
Lobelia erinus
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Campanulaceae
Subfamily: Lobelioideae
Genus: Lobelia
L.[1]
Type species
Lobelia cardinalis
Species
Synonyms[3]
List
    • Mecoschistum Dulac
    • Rapuntium Mill.
    • Dortmanna Hill
    • Cardinalis Fabr.
    • Laurentia Michx. ex Adans.
    • Chamula Noronha
    • Pratia Gaudich.
    • Holostigma G.Don
    • Tupa G.Don
    • Enchysia C.Presl
    • Hypsela C.Presl
    • Trimeris C.Presl
    • Tylomium C.Presl
    • Rhynchopetalum Fresen.
    • Isolobus A.DC.
    • Piddingtonia A.DC.
    • Holostigmateia Rchb.
    • Colensoa Hook.f.
    • Speirema Hook.f. & Thomson
    • Euhaynaldia Borbás
    • Dortmannia Kuntze
    • Galeatella (E.Wimm.) O.Deg. & I.Deg. in O.Degener
    • Neowimmeria O.Deg. & I.Deg
    • Calcaratolobelia Wilbur
Lobelia erinus in an alpine border

Lobelia (/loʊˈbiːliə, lə-/[4][5][6]) is a genus of flowering plants in the family Campanulaceae comprising 415 species,[7] with a subcosmopolitan distribution primarily in tropical to warm temperate regions of the world, a few species extending into cooler temperate regions.[8] They are known generally as lobelias.[9]

Lobelia boninensis

Description

[edit]

The genus Lobelia comprises a substantial number of large and small annual, perennial and shrubby species, hardy and tender, from a variety of habitats, in a range of colours. Many species appear totally dissimilar from each other. However, all have simple, alternate leaves and two-lipped tubular flowers, each with five lobes. The upper two lobes may be erect while the lower three lobes may be fanned out. Flowering is often abundant and the flower colour intense, hence their popularity as ornamental garden subjects.[10]

Taxonomy

[edit]

The genus Lobelia was first formally described in 1753 by Carl Linnaeus in Species plantarum and was named after the Flemish botanist Matthias de Lobel (1538–1616).[11][12][13]

Lobelia is probably the base form from which many other lobelioid genera are derived; it is therefore highly paraphyletic and not a good genus in a cladistic sense. For example, the Hawaiian species (see Hawaiian lobelioids), currently classified in several genera, originated from a single introduction to a now-submerged Hawaiian island 15 million years ago, probably from an Asian Lobelia in Lobelia subg. Tupa.[14]

A New Zealand study concluded that local species of Hypsela, Isotoma and Pratia should be treated as Lobelia.[15]

Species list

[edit]

See List of Lobelia species

Ecology

[edit]

Lobelia species are used as food plants by the larvae of some Lepidoptera species including the Setaceous Hebrew Character.

Cultivation and uses

[edit]

Several species are cultivated as ornamental plants in gardens. These include Lobelia cardinalis syn. Lobelia fulgens (cardinal flower or Indian pink), Lobelia siphilitica (blue lobelia), and Lobelia erinus, which is used for edging and window boxes.[10]

Hybrids

[edit]

Numerous hybrids have been produced, notably Lobelia × speciosa, a hybrid derived from L. fulgens, L. cardinalis and L. siphilitica. The term "fan hybrids" is also used.[16] This plant is borderline hardy and requires fertile, moist soil. It is suitable for summer bedding schemes or growing in containers. The cultivars 'Kompliment Scharlach'[17] and 'Pink Elephant'[18] have gained the Royal Horticultural Society's Award of Garden Merit.[19]

Traditional medicine

[edit]

The species used most commonly in modern herbalism is Lobelia inflata (Indian tobacco).[20] Use of lobelia for cardiovascular diseases may cause adverse effects.[21]

Lobelia has been used as "asthmador" in Appalachian traditional medicine.[22] Two species, L. siphilitica and L. cardinalis, were once considered a cure for syphilis.[23] Herbalist Samuel Thomson popularized medicinal use of lobelia in the United States in the early 19th century.[20]

Adverse effects

[edit]

Many members of the genus are considered poisonous, with some containing the toxic principle lobeline.[24] Because of lobeline's similarity to nicotine, the internal use of lobelia may be dangerous to susceptible populations, including children, pregnant women,[25] and individuals with cardiac disease. Excessive use will cause nausea and vomiting.[26] It is not recommended for use by pregnant women and is best administered by a practitioner qualified in its use. It also has a chemical known as lobellicyonycin,[citation needed] which may cause dizziness.

Chemical constituents

[edit]
Lobelane[27]
Isolobelanine

Extracts of Lobelia inflata contain lobeline[28] and those from Lobelia chinensis contain apigenin, lobeline, lobelanine, isolobelanine, lobelanidine, quercetin, coumarins, glucosides and other flavonoids.[29]

Lobelia sessilifolia
Giant lobelias (Lobelia deckenii), Mount Kenya

Mexican spurred lobelias

[edit]

About eleven species native to Mexico and Central America have spurs on the flowers. These spurred lobelias appear to form a monophyletic group. Most have been classified in the genera Heterotoma (or sometimes Calcaratolobelia). However, since their closest relatives such as Lobelia anatina are in Lobelia, Koopman and Ayers classify them in Lobelia.[30]

References

[edit]

Bibliography

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Lobelia

View on Grokipedia
from Grokipedia
Lobelia is a of flowering plants in the family Campanulaceae, comprising approximately 415 of primarily herbaceous perennials, though some are annuals, subshrubs, or shrubs. The genus exhibits a , with its center of diversity in tropical and subtropical regions, including high-elevation montane habitats, and extends into temperate zones worldwide. Named after the Flemish and physician Matthias de Lobel (1538–1616), who served as royal physician to King James I of , the genus was formally described by in 1753. Species of Lobelia are characterized by alternate leaves that are often simple and toothed, and by irregular, resupinate flowers typically arranged in terminal racemes or spikes, featuring a two-lipped corolla with the upper lip split into two lobes and the lower into three. Many species produce milky and are known for their vibrant blue, purple, red, or white blooms, which attract pollinators such as bees and hummingbirds. While most are terrestrial growing in moist to wet environments like stream banks, meadows, and woodlands, some are aquatic or semi-aquatic, adapted to shallow waters. The genus holds ecological and horticultural significance, with several serving as ornamentals in gardens due to their colorful flowers and adaptability to borders or hanging baskets, particularly in cooler climates. Certain Lobelia , such as L. inflata, have been used in for respiratory ailments owing to their alkaloids, though their toxicity limits modern therapeutic use and they are not recommended without medical supervision. Taxonomically, Lobelia is polyphyletic and part of the larger subfamily Lobelioideae, which includes about 1,200 across 33 genera, prompting ongoing revisions to its classification based on molecular and morphological data.

Morphology

Vegetative Features

The Lobelia comprises , herbaceous, and shrubby , distinguished by their simple, alternate leaves and varied growth forms adapted to diverse environments. Leaves are typically lanceolate, ovate, elliptic, or oblanceolate in shape, with lengths ranging from less than 3 cm in smaller to 10–30 cm in larger ones, and margins that are often denticulate, toothed, or entire. These leaves arise alternately along the stems and may form basal rosettes in some , contributing to the plant's overall compact or upright posture. Stems in Lobelia species are generally erect or ascending, herbaceous in most annuals and perennials but woody at the base or throughout in shrubby forms. Heights vary widely, from 5–15 cm in dwarf herbaceous types to over 1 m in robust perennials and subshrubs, with pubescence ranging from glabrous to densely hairy depending on the species and habitat. Growth habits reflect the genus's ecological versatility, including compact bushy forms in annuals, clump-forming rosettes in wetland perennials, and more sprawling or ascending structures in shrubs. For instance, L. erinus, a popular annual, develops compact, bushy growth with trailing or upright stems 10–23 cm tall and narrow, linear-serrate leaves up to 1.3 cm long, ideal for edging borders. In contrast, the perennial L. cardinalis produces tall, unbranched, erect stems reaching 60–120 cm, bearing lance-shaped, finely toothed leaves up to 10 cm long that form loose basal clusters.

Reproductive Structures

The flowers of Lobelia species are zygomorphic, exhibiting bilateral with a tubular corolla divided into two s: an upper formed by two narrower lobes and a lower by three broader lobes. The corolla, typically measuring 1–5 cm in length, displays a range of colors including blue, red, purple, or white, and is adapted for specific pollinators through its elongated structure. These flowers are bisexual and arranged in inflorescences that are usually terminal racemes or spikes, with bracts that often resemble leaves or are reduced in size. Pollination in Lobelia is primarily entomophilous, facilitated by such as bees and hummingbirds, which access nectar via the tubular corolla while transferring from the fused anthers. The is inferior, positioned below the attachment of the corolla and calyx, leading to the development of capsular fruits after fertilization. These dehiscent capsules typically split open along valves or pores to release numerous tiny seeds, often semi-translucent and oval in shape, enabling wind or animal dispersal. In , the vivid scarlet flowers, measuring about 2.5–5 cm long, form dense terminal racemes and are specialized for , with the elongated corolla excluding most while allowing birds to probe deeply for nectar. Conversely, produces smaller pale blue to purplish flowers in loose racemes, culminating in distinctive inflated seed capsules that dehisce to disperse minute seeds, a trait reflected in its common name, Indian tobacco.

Taxonomy

Classification History

The genus Lobelia was formally established by in his 1753 publication , where he named it in honor of the Flemish and physician Matthias de l'Obel (1538–1616), who had contributed significantly to early botanical studies in . This naming reflects de l'Obel's influence on plant classification, particularly his work on distinguishing monocotyledons from dicotyledons. Lobelia is classified within the family Campanulaceae, specifically the subfamily Lobelioideae, which is distinguished by its resupinate, zygomorphic flowers and connate anthers. The type species, L. cardinalis, was designated in 1929 to stabilize the genus's nomenclature amid ongoing taxonomic revisions. Early 19th-century classifications expanded the genus significantly; for instance, in his 1839 Prodromus Systematis Naturalis Regni Vegetabilis divided Lobelia into three sections based on morphological traits such as corolla shape and capsule dehiscence, incorporating numerous and species into a broader circumscription. Modern phylogenetic analyses, beginning in the early , have revealed the of Lobelia as traditionally defined, with molecular data from genes like rbcL, ndhF, and trnL-F showing that many segregated genera nest within it. This has prompted proposals to merge taxa such as Hypsela into Lobelia, supported by research on species in 2008, which used chloroplast DNA sequences to demonstrate close relationships and synonymize Hypsela and parts of Isotoma under Lobelia. These studies highlight the genus's complex evolutionary history, derived from bellflower () ancestors within Campanulaceae during the , with major diversification occurring in the epoch (approximately 23–5 million years ago), driven by tectonic uplift and climatic shifts in the and other regions.

Species Diversity

The genus Lobelia encompasses approximately 442 accepted species as of 2025, reflecting a diverse array of growth forms such as terrestrial herbs, aquatic perennials, and epiphytic shrubs, though taxonomic revisions continue to refine this count based on molecular and morphological evidence. Infrageneric classification divides the genus into 18 sections, including sect. Lobelia, which predominantly features temperate herbaceous species from and , and sect. Stenotium, the most species-rich group with over 150 tropical shrubs and herbs mainly from and . Notable examples include L. erinus, a South African annual widely used as a bedding ; L. inflata, a North American herb historically employed in ; L. chinensis, an Asian perennial herb; and L. boninensis, an endangered Japanese endemic restricted to the . Species diversity peaks in , home to over 160 species (about 37% of the ), particularly in montane and afro-alpine habitats, followed by substantial representation in American tropical regions; molecular phylogenetic studies in the 2020s have prompted reclassifications, incorporating new taxa and clarifying evolutionary relationships within these hotspots.
Scientific NameCommon NameRegionConservation Status
L. cardinalisCardinal flowerLeast Concern
L. erinusGarden lobeliaLeast Concern
L. inflataIndian tobaccoNot Assessed
L. siphiliticaGreat blue lobeliaLeast Concern
L. chinensisChinese lobeliaLeast Concern
L. boninensisBonin lobelia (Bonin Islands)Endangered
L. dortmannaWater lobeliaNorth temperate zonesLeast Concern
L. laxifloraLooseflower lobeliaNot Assessed
L. tupaDevil's ()Vulnerable
L. boykiniiBoykin's lobeliaSoutheastern USAState Endangered
L. telekiiMount Kenya lobeliaLeast Concern
L. alsinoidesFalse chickweed lobelia and Least Concern
L. nicotianifolia lobeliaLeast Concern

Distribution and Ecology

Geographic Range

The genus Lobelia exhibits a subcosmopolitan distribution, occurring across most continents but largely absent from arid deserts and polar regions. With 442 accepted species as of 2025, the majority—over 300—are concentrated in tropical and subtropical areas, particularly in montane forests of and , where diversity peaks in East African highlands and Asian tropical elevations. In the , Lobelia species are widespread from North to , with notable presence in North American wetlands, such as L. cardinalis along rivers and marshes from to . hosts few native species, primarily aquatic ones like L. dortmanna in northern temperate lakes and streams across to . features endemic clusters, especially in with around 12 small herbaceous species in damp forests and alpine zones, while Pacific islands, including , support unique giant lobelias adapted to volcanic terrains. Historical migration patterns include post-glacial expansions in temperate zones, where species like those in recolonized northern latitudes following the Pleistocene ice ages. Some species show invasive potential outside native ranges, such as L. chinensis establishing in n wetlands after introduction from . Overall, the genus spans predominantly tropical to warm temperate biomes, with altitudinal ranges from to over 4,000 m in Andean and other montane species.

Habitat and Interactions

Lobelia species predominantly inhabit moist environments, including meadows, stream banks, bogs, and forest edges, where they thrive in or semi-aquatic conditions with consistent moisture. Some species, such as Lobelia dortmanna, are fully aquatic, occupying oligotrophic lakes and softwater ponds across and , where they root in sediments and photosynthesize submersed. In tropical regions, certain species exhibit epiphytic growth forms, particularly among , which cling to tree trunks or rocks in montane forests and swamps, adapting to humid, shaded microhabitats. Ecological interactions of Lobelia involve mutualistic relationships that support their reproduction and survival. Flowers are primarily pollinated by long-tongued , including bumblebees for blue-flowered species like L. siphilitica and hummingbirds for red-flowered ones like L. cardinalis, due to the tubular corolla structure that restricts access to smaller pollinators. Several serve as larval host plants for , such as great blue lobelia (L. siphilitica) supporting caterpillars of the blurry-patched nola (Nola cilicoides). Additionally, many Lobelia form arbuscular mycorrhizal associations with fungi, which enhance and nutrient uptake in nutrient-poor soils, with local adaptations observed in populations of L. siphilitica. Conservation challenges for Lobelia are significant, driven primarily by habitat loss and . For instance, Lobelia boninensis, endemic to the , is critically endangered due to predation by introduced rats and competition from invasive plants like Miscanthus sinensis, reducing its populations on coastal cliffs. In , ethnobotanical harvesting for traditional uses exacerbates pressures on montane species. Recent 2024 studies indicate that , through altered precipitation and temperature regimes, threatens giant Lobelia populations in East African afro-alpine habitats by shifting suitable climatic niches. Lobelia plays key ecological roles in natural and restored ecosystems, particularly as a in . Species like L. dortmanna act as keystone components in oligotrophic ponds, stabilizing sediments and facilitating community assembly in softwater habitats during restoration efforts. In riverine and restorations, such as blue lobelia (L. siphilitica) help prevent along banks while supporting recovery.

Cultivation

Ornamental Practices

Lobelia species, particularly L. erinus and hybrids such as L. × speciosa, are widely valued in ornamental for their cascading displays of tubular flowers in , white, and violet, making them ideal for borders, hanging baskets, and edges of water gardens. These provide a low-growing, trailing that adds vibrant color and texture to landscapes, with flowers attracting visual interest from spring through fall in suitable climates. L. erinus and similar tender varieties thrive in full sun to partial shade, depending on regional heat levels, with consistently moist, well-drained soil enriched with to maintain even moisture without waterlogging. A range of 6.0 to 7.0 supports healthy growth, and plants thrive in cooler temperatures but may require afternoon shade in hotter areas to prevent scorching. These are hardy in USDA zones 9 to 11 and treated as annuals in cooler regions where frost is a concern. Hybrids like L. × speciosa, derived from crosses involving L. cardinalis, L. siphilitica, and L. fulgens, are hardier, typically in USDA zones 5 to 9. Notable hybrids and cultivars enhance ornamental appeal through varied foliage and flower forms; for instance, features compact growth with dark bronze foliage contrasting deep blue flowers, suitable for edging or containers, while 'Cambridge Blue' offers pale blue blooms for softer color schemes in baskets. The L. × speciosa group produces upright to trailing forms with bold blue or red flowers, and breeding efforts have focused on improving vigor through polyploidisation. Historically, Lobelia gained popularity during the as a favorite for formal edgings and mass plantings in elaborate schemes, prized for its neat and profuse blooming. In contemporary , it serves as a key component in pollinator-friendly designs, drawing bees and hummingbirds to support in mixed borders or naturalistic settings.

Propagation Methods

Lobelia species can be propagated through or vegetative means, with methods varying by whether the plant is an annual like L. erinus or a perennial such as L. cardinalis. propagation is the most common approach for many , involving surface to allow exposure, which is essential for . Seeds should be sown in spring on a moist, sterile medium without covering them, as aids the process. typically occurs in 10-20 days at temperatures of 18-21°C (65-70°F), though some perennials benefit from cold stratification—placing moist seeds at 1-3°C (34-37°F) for 30 days prior to —to break and improve rates. For perennials like L. cardinalis, fresh seeds collected in early fall from inflated pods can be sown directly or stratified for better results, yielding high in moist conditions with light exposure. Annuals such as L. erinus germinate readily without stratification when started indoors 10-12 weeks before the last , using a well-draining seed-starting mix kept consistently damp via misting. Post-germination, seedlings require bright, indirect light and careful watering to avoid over-saturation, with occurring once true leaves develop. Vegetative propagation offers reliable cloning for desirable traits, particularly in perennials and shrubs. Division is effective for clump-forming species like L. cardinalis, where basal rosettes are separated in spring or fall from established plants, replanted immediately in moist soil to maintain root integrity. Stem cuttings suit shrubby types such as L. tupa, taken as 10 cm basal shoots in spring and rooted in a peat-perlite mix under high humidity, often with rooting hormone to promote uniform root development. Layering provides another option for L. cardinalis, bending stems to the soil in midsummer, securing nodes under a thin layer of earth until roots form at the contact points. Challenges in include damping-off in seedlings, caused by fungal pathogens in overly wet, unsterilized media, which can be mitigated by using pasteurized , ensuring good , and maintaining optimal temperatures for rapid growth. is a viable method for species like L. bridgesii, enabling rapid multiplication from shoot tips , with protocols achieving high survival rates (73-100%) upon acclimation. Timing is crucial for success; stem cuttings root best in late summer under or plastic covers to retain moisture, while divisions and layering align with active growth periods. For tender perennials like L. erinus in cold climates (USDA zones below 9), propagated plants should be overwintered indoors in a cool, bright location to prevent frost damage, ensuring they establish before the next growing season; hardier species like L. cardinalis (zones 3-9) can remain outdoors.

Uses

Traditional Medicine

Lobelia species have been integral to traditional medicine across various cultures, particularly for respiratory ailments and as emetics. In Native American traditions, Lobelia inflata, known as Indian tobacco, was widely employed for treating asthma, bronchitis, and other respiratory conditions, often serving as an emetic to induce vomiting for detoxification. Tribes such as the Cherokee and Iroquois used the leaves and roots, either smoked like tobacco for relief from bronchial spasms or prepared as teas to alleviate coughs and promote expectoration. In Asian herbal practices, Lobelia chinensis held prominence in , documented as early as the 16th century for addressing through its properties and for treating snakebites to reduce swelling and . This species was valued for clearing heat and promoting urination to resolve associated with inflammatory conditions, reflecting its role in balancing vital energies as per classical texts. Across other regions, European folk remedies featured Lobelia dortmanna for soothing sore throats and respiratory irritations. These uses underscore the plant's broad ethnobotanical significance in pre-modern healing systems. Traditional preparations of Lobelia involved infusions, tinctures, or poultices to extract its active properties, with historical therapeutic dosages typically ranging from 100 to 400 mg of dried leaf per administration, though caution is advised if exceeding 1 g daily due to risks. Such methods allowed for targeted application, whether internally for respiratory relief or externally for localized .

Modern Applications

In contemporary , extracts of are incorporated into dietary supplements marketed for respiratory support, particularly to alleviate coughs and promote expectoration. These products, often available as tinctures or capsules, leverage the plant's lobeline content for its purported bronchodilatory and expectorant properties. A 2025 review highlighted the potential of L. inflata in managing post-COVID-19 respiratory complications, such as , by facilitating clearance and reducing in affected airways, based on its traditional expectorant mechanisms supported by preliminary clinical observations. Recent research has explored the anticancer properties of Lobelia , with a 2025 study demonstrating that ethanolic extracts of L. nummularia inhibit proliferation in cells (MDA-MB-231 line) by inducing (ROS)-dependent mitochondrial . This effect involves targeting EGFR/TP53 and PI3K-AKT-mTOR signaling pathways, suggesting a mechanism for selective against malignant cells while sparing normal ones. Such findings underscore the plant's bioactive alkaloids as candidates for further chemotherapeutic investigation, though human trials remain pending. Additional applications include antimicrobial effects observed in Lobelia species. For instance, essential oil from L. pyramidalis has shown moderate activity against Staphylococcus aureus and Escherichia coli, attributed to its compounds. A 2025 study on L. alsinoides ethanolic extract demonstrated antimicrobial activity against methicillin-resistant S. aureus (MRSA) in wound healing models. Anti-inflammatory effects have been noted in preclinical models, where extracts reduce pro-inflammatory cytokines, potentially benefiting conditions like arthritis by modulating oxidative stress. Pharmaceutical development is limited by toxicity concerns. Regulatory oversight varies globally; the U.S. (FDA) deems L. inflata unsafe for self-medication, prohibiting over-the-counter sales of lobeline products since 1993 due to insufficient efficacy and safety data. In contrast, herbal Lobelia preparations, including L. chinensis extracts, are permitted in under traditional herbal medicinal product directives for short-term respiratory use as of 2025, and in , they are commonly sold as supplements in countries like and with established pharmacopeial standards.

Chemical Constituents

Alkaloids

The genus Lobelia is characterized by alkaloids as its primary chemical class, with serving as the predominant due to its structural similarity to and molecular formula C22_{22}H27_{27}NO2_{2}. features a ring with two phenyl-substituted side chains, one bearing a hydroxyl group, contributing to its bioactive properties. Related alkaloids include lobelanine, an oxidized derivative of , and isolobelanine (also known as norlobelanine), both sharing the core scaffold but differing in substitution patterns. These alkaloids constitute the main bioactive constituents, with total concentrations ranging from 0.24% to 0.4% of dry weight in . Biosynthesis of these piperidine alkaloids in Lobelia species proceeds from the and . The nucleus forms via decarboxylation and cyclization of through a Δ¹-piperideine intermediate, while provides the C₆–C₂ side chain units via derivatives. Lobelanine functions as a key symmetrical intermediate in the pathway leading to lobeline, involving dimerization of an α-phenacyl precursor. This dual precursor route underscores the alkaloids' hybrid origin, blending -derived rings with phenylpropanoid extensions. Lobeline exhibits a pharmacological profile as a at nicotinic receptors, particularly the α₄β₂ subtype, eliciting respiratory stimulation at low doses through activation. Extraction and analysis of these alkaloids typically involve solvent partitioning followed by chromatographic separation. Initial isolation uses alkaline extraction with organic solvents like ether, succeeded by silica gel column chromatography or high-performance liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS) for purification and identification. These methods enable quantification of lobeline and congeners, confirming their structural integrity and purity for pharmacological studies. Alkaloid content varies significantly across Lobelia species, with the highest concentrations observed in the North American L. inflata, where lobeline dominates the profile. In contrast, ornamental species like L. erinus exhibit substantially lower levels of these alkaloids, often in trace amounts insufficient for medicinal extraction. This variation reflects ecological adaptations, with L. inflata accumulating higher defenses in its native habitats compared to cultivated ornamentals. Other , such as L. sessilifolia, contain distinct polyacetylenes, highlighting chemical diversity in the genus.

Other Compounds

In addition to alkaloids, species of Lobelia contain various secondary metabolites, including , which exhibit antioxidant properties. In L. chinensis, key identified include , , , luteolin 7-O-glucoside, and , primarily isolated from aerial parts such as leaves. These compounds contribute to the plant's response and have been linked to broader protective effects in Lobelia species. Polyacetylenes and coumarins are prominent in Asian Lobelia species, particularly L. chinensis. Notable polyacetylenes include lobetyolin, a found in the whole , alongside related compounds like lobetyol and isolobetyol. Coumarins such as scoparone, isoscopoletin, and 5,7-dimethoxy-8-hydroxycoumarin have also been characterized from L. chinensis. Recent cultivation studies have demonstrated enhanced accumulation of these polyacetylenes and associated phenolics through elicitation with and in plantlet cultures, increasing yields by up to several-fold compared to controls. These compounds, along with and polyacetylenes, play roles in defense mechanisms, including deterrence of herbivores through and repellency. (HPLC), often coupled with (e.g., HPLC/Q-TOF MS or LC-ESI-MS/MS), is commonly employed for the quantification and profiling of these metabolites in Lobelia extracts.

Safety and Toxicity

Adverse Effects

Exposure to Lobelia, particularly through , can lead to acute symptoms such as , , tremors, profuse sweating, , , and , primarily resulting from the overstimulation of nicotinic receptors by its primary , lobeline. These effects typically onset within 30 to due to the rapid absorption of lobeline from the . In severe cases of overdose, symptoms may escalate to respiratory depression, convulsions, , and potentially , particularly at doses of 4 g or more of the plant material. Historical records from 19th-century include accusations of fatalities, such as the 1809 case where practitioner Samuel Thomson was accused of causing a patient's through excessive Lobelia administration but was acquitted at . Lobelia alkaloids can cause neurotoxic effects such as convulsions and cardiac disturbances like arrhythmias in animal studies at high acute doses. Poisoning reports include incidents from consumption of Lobelia-containing teas, which have induced , respiratory distress, convulsions, and in cases of excessive intake. In rodent models, the (LD50) of lobeline is approximately 40 mg/kg via intraperitoneal administration, underscoring its toxicity threshold.

Contraindications

Lobelia is contraindicated for pregnant and women due to its potential to cause serious and loss of uterine tone, posing risks to fetal development and . It should also be avoided by children under 12 years old, as insufficient safety data exist and toxicity risks are heightened in pediatric populations. Individuals with heart conditions are advised against its use, given lobelia's cardioactive effects that can lead to , , or other cardiac disturbances. Similarly, those with or disorders should avoid lobelia, as it may trigger convulsions despite some isolated reports of potential properties in controlled settings. Regarding drug interactions, lobelia potentiates the effects of due to its lobeline content, which acts as a and can amplify CNS stimulation or respiratory impacts when combined. It is contraindicated with antihypertensives, as lobelia's hypotensive properties may excessively lower , and with sedatives, potentially enhancing CNS depression and leading to excessive drowsiness or respiratory issues. Regulatory warnings highlight lobelia's restricted status; it is restricted for internal medicinal use in the (maximum single dose 200 mg, daily 600 mg, available only in registered pharmacies under supervision), with limited external applications also permitted under strict guidelines. In , it is not sold for internal consumption due to concerns, though low concentrations (e.g., ≤0.001% or 10 mg/kg) are permitted in listed medicines but not for internal therapeutic claims. The U.S. FDA has prohibited over-the-counter lobeline products for since 1993 due to lack of efficacy and safety concerns. Individuals considering lobelia should consult healthcare providers prior to use, particularly those with sensitivities, as handling the plant may induce allergic in some cases.

References

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