Dagga

In Trinidad the plant is called shandilay. In a survey of 450 rural households it was the most-cited medicinal plant of all, named 89 times, 85 of them for coughs and the common cold ^{24Reference 24Clement YN et al. · 2015ObservationalAn ethnobotanical survey of medicinal plants in Trinidad — ethnobotanical/observational surveyView study →}.

The leaves are taken as an infusion or a decoction, or pounded and squeezed and the juice taken with salt. A few informants also used it for fever or as a “cooling” remedy ^{24Reference 24Clement YN et al. · 2015ObservationalAn ethnobotanical survey of medicinal plants in Trinidad — ethnobotanical/observational surveyView study →}.

In Brazil the plant is known as cordão-de-frade. It is used for infections, inflammation, wounds and stomach complaints ^{8,10Reference 8Oliveira DM et al. · 2015In vitroAntibacterial mode of action of the hydroethanolic extract of Leonotis nepetifolia (L.) RView study →Reference 10de Oliveira DP et al. · 2021In vitroExploring the bioactivity potential of Leonotis nepetifolia: phytochemical composition, antimicrobial and antileishmanial activities of extracts from different anatomical parts — in vitroView study →}.

In a survey in western Uganda, dagga was among the most frequently cited of 67 medicinal plants ^{25Reference 25Gumisiriza H et al. · 2021Medicinal plants used to treat “African” diseases by the local communities of Bwambara sub-county in Rukungiri District, Western Uganda — ethnobotanical surveyView study →}. In Rwanda the leaves are used for pneumonia ^{31Reference 31Fern KLeonotis nepetifoliaView study →}.

It is also used as a calming remedy, a traditional use described by researchers in Nigeria ^{18Reference 18Ayanwuyi LO et al. · 2016AnimalPreliminary studies on the behavioural effects of the methanol extract of Leonotis nepetifolia Linn stem in mice — in vivo behavioural (animal model)View study →}.

Two furanolabdane diterpenoids isolated from the leaves, nepetaefuran and leonotinin, suppressed LPS-induced nitric oxide and CCL2 production in macrophages. They did so by blocking the transcriptional activity of NF-κB, without affecting the MAP-kinase pathway. A third diterpenoid, leonotin, was inactive ^{4Reference 4Ueda F et al. · 2015In vitroNepetaefuran and leonotinin isolated from Leonotis nepetaefolia RView study →}.

A 2025 study of the leaf essential oil (mainly germacrene D, β-caryophyllene, α-humulene and phytol) reproduced this in LPS-stimulated RAW 264.7 macrophages. The oil lowered TNF-α, IL-1β, IL-6, iNOS and COX-2, dampened intracellular ROS, suppressed TLR4/MyD88 and NF-κB p65, and induced the Nrf2/HO-1 antioxidant pathway ^{5Reference 5Mohanta O et al. · 2025In vitroAnti-inflammatory activity of Leonotis nepetifolia leaf essential oil in LPS-stimulated RAW 264.7 cells and its molecular mechanism of action — in vitro macrophage modelView study →}.

Separately, transformed-root extracts blunted rhinovirus-induced IL-6 and IL-1β in airway and gingival cell lines ^{6Reference 6Sitarek P et al. · 2023In vitroLeonotis nepetifolia transformed root extract reduces pro-inflammatory cytokines and promotes tissue repair in vitro — in vitro airway/gingival cell modelView study →}.

Gap: all in vitro, plus one root-culture system. There is no animal model of inflammation and no human data, and the most complete study used the essential oil rather than the infused or smoked leaf.

Antimicrobial activity has been found by several independent groups across different preparations. A hydroethanolic leaf extract was active against Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis and Shigella flexneri (MIC 6.25 µg/mL) and against Helicobacter pylori (MIC 25 µg/mL). It acted at least partly by making bacterial membranes more permeable, and it was not toxic to mammalian cells (IC50 > 200 µg/mL) ^{8Reference 8Oliveira DM et al. · 2015In vitroAntibacterial mode of action of the hydroethanolic extract of Leonotis nepetifolia (L.) RView study →}.

Essential oils are consistently active against Gram-positive bacteria, fungi and dermatophytes ^{7,9,12Reference 7Gopal RH et al. · 1994In vitroAntimicrobial activity of essential oil of Leonotis nepetaefolia — in vitroView study →Reference 9Casiglia S et al. · 2014In vitroActivity against microorganisms affecting cellulosic objects of the volatile constituents of Leonotis nepetaefolia from Nicaragua — in vitroView study →Reference 12Adolpho LO et al. · 2024In vitroChemical profile and antimicrobial activity of Leonotis nepetifolia (L.) RView study →}, with germacrene D and β-caryophyllene the dominant volatiles ^{12Reference 12Adolpho LO et al. · 2024In vitroChemical profile and antimicrobial activity of Leonotis nepetifolia (L.) RView study →}.

A leaf extract also inhibited Bacillus cereus, S. aureus and Candida ^{10Reference 10de Oliveira DP et al. · 2021In vitroExploring the bioactivity potential of Leonotis nepetifolia: phytochemical composition, antimicrobial and antileishmanial activities of extracts from different anatomical parts — in vitroView study →}. Flower-bud extracts inhibited a panel of bacterial and fungal pathogens ^{11Reference 11Nagaraja SK et al. · 2023In vitroPhytochemical analysis, GC-MS profiling, and in vitro evaluation of biological applications of different solvent extracts of Leonotis nepetifolia (L.) R.Br. flower buds — in vitroView study →}, and flower powder fully suppressed aflatoxin-producing Aspergillus flavus at 10 mg/mL ^{13Reference 13Abubacker MN · 2003In vitroEfficacy of Euphorbia splendens and Leonotis nepetaefolia on aflatoxin-producing fungi Aspergillus flavus and Aspergillus parasiticus — in vitroView study →}.

Gap: moderate activity in the µg–mg/mL range, entirely in vitro, with no infection model and no data on levels reached in the body.

A methanol extract produced antidepressant-like effects in mice, reducing immobility in the tail-suspension and forced-swim tests. Over 28 days it also improved body-weight gain and lowered corticosterone in chronically stressed animals, pointing to the hypothalamic-pituitary-adrenal axis. The extract’s main compounds were nepetaefolin, methoxynepetaefolin and luteolin-7-glucoside ^{17Reference 17Arrieta-Báez D et al. · 2022AnimalAntidepressant-like effects of a methanol extract of Leonotis nepetifolia in mice — in vivo behavioural (animal model)View study →}.

An earlier study of a methanol stem extract found anxiety-reducing signals at 150 mg/kg: fewer rearings in the staircase test and longer diazepam-induced sleep. It had no effect on exploration or motor coordination, and its LD50 by intraperitoneal injection was 3.8 g/kg ^{18Reference 18Ayanwuyi LO et al. · 2016AnimalPreliminary studies on the behavioural effects of the methanol extract of Leonotis nepetifolia Linn stem in mice — in vivo behavioural (animal model)View study →}.

Bis-spirolabdane diterpenoids isolated from the leaves were screened against CNS G-protein-coupled receptors in vitro ^{3Reference 3Li J et al. · 2012In vitroBis-spirolabdane diterpenoids from Leonotis nepetaefolia — in vitro CNS G-protein-coupled receptor bindingView study →}. The flavone cirsiliol, a marker compound of this species, has shown sedative and hypnotic activity in other research ^{19Reference 19de Oliveira AP et al. · 2019Influence of light intensity, fertilizing and season on the cirsiliol content, a chemical marker of Leonotis nepetifolia (Lamiaceae) — cultivation/chemical markerView study →}.

Gap: two small mouse studies of methanol extracts, testing sedation and mood rather than any euphoric effect. None of this work used the smoked herb.

Flower-bud methanol extract reached 74% DPPH inhibition at 1000 µg/mL, rising with concentration ^{11Reference 11Nagaraja SK et al. · 2023In vitroPhytochemical analysis, GC-MS profiling, and in vitro evaluation of biological applications of different solvent extracts of Leonotis nepetifolia (L.) R.Br. flower buds — in vitroView study →}, and L. nepetifolia was among the more active species in a screen of Brazilian Caatinga plants ^{14Reference 14David JP et al. · 2007In vitroRadical scavenging, antioxidant and cytotoxic activity of Brazilian Caatinga plants — in vitro DPPH/brine-shrimpView study →}.

Transformed- and normal-root extracts scavenged radicals and protected HUVEC cells against H2O2-induced DNA damage ^{15Reference 15Kowalczyk T et al. · 2021In vitroPreliminary phytochemical analysis and evaluation of the biological activity of Leonotis nepetifolia (L.) RView study →}, and silver-nanoparticle preparations showed concentration-dependent DPPH activity ^{16Reference 16Nagaraja SK et al. · 2022In vitroLeonotis nepetifolia flower bud extract mediated green synthesis of silver nanoparticles, their characterization, and in vitro evaluation of biological applications — in vitroView study →}.

The leaf essential oil raised SOD, GSH, GPx and catalase and activated Nrf2/HO-1 in macrophages ^{5Reference 5Mohanta O et al. · 2025In vitroAnti-inflammatory activity of Leonotis nepetifolia leaf essential oil in LPS-stimulated RAW 264.7 cells and its molecular mechanism of action — in vitro macrophage modelView study →}, linking the antioxidant and anti-inflammatory findings.

Gap: chemical-assay and cell-line work with no in-vivo endpoint. Several positive results come from engineered preparations such as nanoparticles and transformed root cultures.

The species-marker flavone cirsiliol, made more soluble as a β-cyclodextrin complex, inhibited PC3, HCT-116 and HL-60 human cancer cell lines. It slowed tumour growth in mice bearing sarcoma S-180 without the toxicity of doxorubicin ^{20Reference 20Oliveira AP et al. · 2019In vitroOliveira AP, Silva JC, Silva RM, et al. (2019). β-Cyclodextrin complex improves the bioavailability and antitumor potential of cirsiliol, a flavone isolated from Leonotis nepetifolia (Lamiaceae) — in vitro plus in vivo murine sarcoma model. Heliyon. https://pubmed.ncbi.nlm.nih.gov/31720439/View study →}.

Methanolic transformed-root extracts were cytotoxic to A549 lung, HCC1937 breast and NALM-6 leukaemia cells ^{15Reference 15Kowalczyk T et al. · 2021In vitroPreliminary phytochemical analysis and evaluation of the biological activity of Leonotis nepetifolia (L.) RView study →}. Against melanoma cells they raised p53 expression and pro-apoptotic activity, and docking studies implicated the identified phenolics ^{21Reference 21Merecz-Sadowska A et al. · 2022In vitroIn vitro and in silico studies on Leonotis nepetifolia (L.) RView study →}.

Flower-bud extracts were also anti-proliferative in vitro ^{11Reference 11Nagaraja SK et al. · 2023In vitroPhytochemical analysis, GC-MS profiling, and in vitro evaluation of biological applications of different solvent extracts of Leonotis nepetifolia (L.) R.Br. flower buds — in vitroView study →}.

Gap: the strongest result depends on a solubility-enhanced isolated molecule, and the cell-line effects come from Rhizobium-transformed root cultures, which are genetically modified tissue rather than the plant. Crude root extract IC50s run high, at 760–980 µg/mL.

A single 1991 study tested hydroalcoholic and tea extracts of the stem on isolated rat and guinea-pig tissue. Both relaxed rat uterus precontracted with potassium chloride, the hydroalcoholic extract about twice as potently as the tea. The relaxation was strengthened by IBMX and unaffected by propranolol or forskolin ^{2Reference 2Calixto JB et al. · 1991In vitroEffect of crude extracts from Leonotis nepetaefolia (Labiatae) on rat and guinea-pig smooth muscle and rat cardiac muscle — in vitro isolated-tissue studyView study →}.

Both extracts also blunted the uterine contractions caused by bradykinin and other agonists, and did the same to acetylcholine-induced contractions of guinea-pig ileum ^{2Reference 2Calixto JB et al. · 1991In vitroEffect of crude extracts from Leonotis nepetaefolia (Labiatae) on rat and guinea-pig smooth muscle and rat cardiac muscle — in vitro isolated-tissue studyView study →}.

The pattern suggests a general smooth-muscle relaxant action.

Gap: one isolated-tissue study, with the mechanism unresolved and never replicated. Its effect on uterine muscle is a reason for caution in pregnancy.

Hydroethanolic extracts from different plant parts were tested against Leishmania amazonensis. Leaf and root extracts were the most active against the intracellular amastigote form, the stage relevant to human disease (IC50 32.9 and 57.7 µg/mL). The extracts contained apigenin, cirsiliol and several luteolin glycosides ^{10Reference 10de Oliveira DP et al. · 2021In vitroExploring the bioactivity potential of Leonotis nepetifolia: phytochemical composition, antimicrobial and antileishmanial activities of extracts from different anatomical parts — in vitroView study →}.

Gap: a single in-vitro study at moderate potency, with no selectivity index and no in-vivo follow-up.

In a phytochemical study of the aerial parts, two isolated compounds, the anthraquinone chrysophanol and the sesquiterpenoid (+)-ar-turmerone, inhibited α-glucosidase with IC50 values of 4.9 and 5.3 µg/mL, well below the acarbose control. The newly described triterpenoid nepetifoliol was inactive ^{22Reference 22Nguyen TK et al. · 2023In vitroNepetifoliol — a new glutinane-triterpenoid from Leonotis nepetifolia — phytochemistry, in vitro α-glucosidase inhibitionView study →}.

Gap: enzyme inhibition by minor constituents in one study, with no cellular, animal or blood-sugar data.

Toxicity. There are no human clinical or toxicology studies. In mice, the intraperitoneal LD50 of a methanol stem extract was 3.8 g/kg ^{18Reference 18Ayanwuyi LO et al. · 2016AnimalPreliminary studies on the behavioural effects of the methanol extract of Leonotis nepetifolia Linn stem in mice — in vivo behavioural (animal model)View study →}, and a hydroethanolic leaf extract was not toxic to mammalian cells in vitro (IC50 > 200 µg/mL) ^{8Reference 8Oliveira DM et al. · 2015In vitroAntibacterial mode of action of the hydroethanolic extract of Leonotis nepetifolia (L.) RView study →}.

Pregnancy. Stem extracts relaxed isolated rat uterine muscle and blunted its contractions ^{2Reference 2Calixto JB et al. · 1991In vitroEffect of crude extracts from Leonotis nepetaefolia (Labiatae) on rat and guinea-pig smooth muscle and rat cardiac muscle — in vitro isolated-tissue studyView study →}. In zebrafish embryos, a methanol flower extract and especially its ethyl-acetate fraction were embryotoxic and teratogenic, with effects on acetylcholinesterase, lipid peroxidation and the heart ^{23Reference 23Adolpho L et al. · 2026AnimalComprehensive analysis of Leonotis nepetifolia flower extracts: phytochemical composition and toxicity in zebrafish embryos — in vivo zebrafish toxicityView study →}.

Smoking. Dagga is often smoked or vaped, and no study has examined the safety of inhaling it.

Interactions and allergy. No CYP450 or other interaction study exists for this species. As a mint-family plant, it may cause cross-reactions in people allergic to related herbs, though no case reports were found.