Tulbaghia

Other Names

aandblommetjiefragrant tulbaghiaincinsiniishaladi lezinyokaisihaqaisihihiitswele lomlamboivimbamoelelamothebemotsuntsunyanempunziOmentaria alliacea (L.f.) KuntzeOmentaria Salisb.Omentaria violacea (Harv.) Kuntzepink agapanthusPrototulbaghia Vosasefothafothasikwasociety garlicsoetwildeknoffelsweet garlicsweet wild garlicTulbaghia acutilobaTulbaghia affinis LinkTulbaghia alliaceaTulbaghia alliacea var. affinis BakerTulbaghia brachystemma KunthTulbaghia capensisTulbaghia cepacea var. maritima VosaTulbaghia cepacea var. robustior KunthTulbaghia cernua Avé-Lall.Tulbaghia daviesii GreyTulbaghia fragrans I.Verd.Tulbaghia inodora Gaertn.Tulbaghia narcissiflora Salisb.Tulbaghia pulchella P.E.BarnesTulbaghia simmleriTulbaghia violaceaTulbaghia violacea subsp. macmasteri VosaTulbaghia violacea subsp. violaceaTulbaghia violacea var. minor BakerTulbaghia violacea var. obtusa BakerTulbaghia violacea var. robustior (Kunth) R.B.Burb.utswelanewild garlicwilde knoffelwildeknoffelwildeknoflok

Synopsis

Tulbaghia: A Comprehensive Reference

1. Identity and Botanical Description

1.1 Taxonomy and Nomenclature

Tulbaghia violacea, commonly known as society garlic, pink agapanthus, wild garlic, sweet garlic, spring bulbs, or spring flowers, is a species of flowering plant in the family Amaryllidaceae. The Tulbaghia genus, within the Amaryllidaceae, is indigenous to southern African countries such as Lesotho, Malawi, Botswana, Swaziland, Zimbabwe, and South Africa. The genus comprises about 30 species, of which T. violacea is one of the most studied species for medicinal purposes.

The binomial name Tulbaghia violacea Harv. derives from (i) Ryk Tulbagh — governor of the Cape of Good Hope (1699–1771) — and (ii) the violet flowers of the species, respectively. It is commonly called "wild or society garlic," with other names including "isihaqa/sikwa," "moelela/sefothafotha," "ivimba/mpunzi," and "knoflook/wilde knoffel" in IsiZulu, IsiSotho, IsiXhosa, and Afrikaans, respectively.

Tulbaghia is a monocotyledonous genus of herbaceous perennial bulbs predominantly found in Africa. The genus is endemic to Southern Africa and includes about 20 species, of which only T. alliacea and T. capensis are naturally found in the winter rainfall climate area (the Western Cape). The genus forms part of the Alliaceae family and is a geophyte — a plant with an underground perennation organ and leaves that die back annually.

1.2 Botanical Characteristics

Growing to 60 cm (24 in) tall by 25 cm (10 in) wide, it is a clump-forming perennial with narrow leaves and large clusters of fragrant, violet flowers from midsummer to autumn. Tulbaghia violacea is a spreading, vigorous, clump-forming perennial herb with grass-like foliage and corm-like rhizomes. It is a perennial bulb characterized by long and narrow leaves that produce a garlic-like smell. Its purple flowers are held on thin and long (approximately 30 cm) stalks.

Tulbaghia violacea is a drought-resistant medicinal plant that stretches from the Eastern Cape, KwaZulu-Natal, Northern Gauteng and Limpopo in South Africa to even as far north as Zimbabwe. The plant has been assumed to possess biological activities similar to garlic (Allium sativum) since both belong to the same Alliaceae family and have similar bioactive compounds.

1.3 Relationship to Garlic

Wild garlic is known as such because, although its taste is close to that of real garlic, it is supposed not to leave behind embarrassing bad-breath odours. However, research has challenged this assumption: despite the traditional belief, ingestion of marasmin-rich plants was always accompanied by development of a strong "garlic breath." The leaves of T. violacea are eaten as a substitute for chives and garlic, and Tulbaghia violacea has been used in foods as a garlic replacement.

1.4 Medicinal Plant Parts and Common Preparations

The phytomedicine Tulbaghia consists of the fresh or dried subterranean organs of various Tulbaghia species. Wild garlic is most commonly prepared as an infusion or boiled in water and taken orally. Scientific studies have investigated a variety of extract types from multiple plant parts, including methanol, ethanol, aqueous, acetone, hexane, and dichloromethane extracts of leaves, stems, rhizomes/bulbs, and, more recently, fruits and seeds.

It is grown as an ornamental in botanical gardens and in home gardens all over southern Africa and is cultivated in some overseas countries such as the USA and the UK. This species and the cultivars 'Purple Eye' and 'Silver Lace,' with cream-margined leaves, have all gained the Royal Horticultural Society's Award of Garden Merit.

2. Traditional and Historical Use

2.1 Historical Context

For centuries, several Tulbaghia species have found diverse uses in traditional medicine, with T. violacea remaining the most widely used species. Tulbaghia is an economically important genus with several species being traded locally in southern Africa as medicinal plants for various ailments such as colds, fevers, headaches and intestinal worms, and as a snake repellent.

2.2 Cultures and Practices

In South Africa, Zulu people eat the leaves and flowers as a leaf vegetable like spinach or for seasoning meat and potatoes. Zulu people also use T. violacea, which they refer to as isihaqa, as an aphrodisiac.

In South Africa, this herb has been traditionally used in the treatment of various ailments, including fever, colds, asthma, paralysis, hypertension, and stomach problems. Internally, rhizome or bulb preparations are taken orally to treat fever; as a remedy for colds and influenza, asthma, tuberculosis, and stomach problems; as an antihypertensive; or to expel intestinal worms.

The constituents of Tulbaghia violacea include several odour-forming compounds and bioflavonoids. Its medicinal uses include treatment for fever, colds, asthma, tuberculosis, oesophageal cancer, rheumatism, paralysis, hypertension, and stomach problems.

Wild garlic is traditionally used for fever and colds, but also for asthma and tuberculosis. The leaves are used to treat cancer of the oesophagus.

2.3 Other Species in Traditional Use

Plants in the genus Tulbaghia of the Amaryllidaceae family, especially T. violacea and T. alliacea, have been used as traditional herbal medicines to treat diseases such as asthma, tuberculosis, rheumatism, paralysis, and hypertension in southern Africa. Tulbaghia acutiloba is used in traditional medicine to treat barrenness, flu, and bad breath.

Because both the above-ground and underground parts of Tulbaghia are commonly used in African traditional medicine, destructive harvesting of the whole plant is inevitable, thus necessitating the large-scale organized propagation of these species.

3. Key Constituents and Active Compounds

3.1 Overview of Phytochemistry

Close to 100 compounds have been tentatively identified, largely using gas chromatography techniques, from different parts of T. violacea. Most prominent are the sulfur compounds with reported broad-spectrum pharmacological activity. Phytochemical studies on the genus Tulbaghia have been severely neglected when compared to the closely related genus Allium. Unlike other genera in Amaryllidaceae, Tulbaghia is so far devoid of any alkaloids.

3.2 Sulfur-Containing Compounds: Marasmin and Marasmicin

One of the phytochemical features of the genus Tulbaghia is the production of an S-substituted L-cysteine sulfoxide, marasmin [S-(methylthiomethyl)-L-cysteine-4-oxide], which is a major sulfur-containing secondary metabolite. When plant tissues are disrupted, marasmin is hydrolyzed by endogenous C–S lyase to form an unstable thiosulfinate, marasmicin [S-(methylthiomethyl)(methylthio)methanethiosulfinate].

The thiosulfinate marasmicin is the most prolific antimicrobial compound reported thus far from this genus. This compound is formed from its precursor compound marasmin by the enzyme C-lyase. Marasmicin is responsible for the characteristic garlic odor generated by damaged plants.

Antimicrobial activity of marasmicin was evaluated (MIC 4–64 µg/ml) and compared with that of allicin (MIC 4–32 µg/ml), the prominent bioactive compound of garlic (Allium sativum).

Owing to its unstable nature, marasmicin spontaneously decomposes into various sulfur-containing compounds such as 2,4,5,7-tetrathiaoctane and its oxides. The resulting compounds possess antimicrobial, antifungal, and antithrombotic activities.

Marasmin, which is especially known from T. alliacea and T. violacea, is the precursor of the thiosulfinate marasmicin. Marasmicin has attracted considerable attention because of its antifungal and tuberculostatic activities.

3.3 Volatile Sulfur Compounds

Notable volatile sulfur compounds identified from the aerial parts of T. violacea include allicin (possessing antibacterial and antifungal activity), bis(methylthiomethyl) disulfide (found to constitute 48% of volatiles in aerial parts), methyl-2-thioethyl thiomethyl trisulfide (found to constitute 16% of volatile compounds in aerial parts), and methyl (methylthio)methyl disulfide (found to constitute 10% of volatile compounds in aerial parts).

3.4 Non-Sulfur Constituents

Other notable compounds produced by T. violacea include phenols, tannins, and flavonoids, which are also responsible for several observed biological activities. Burton (1990) identified several free sugars including glucose, fructose, sucrose, maltose, arabinose, rhamnose, xylose, and glycosides in water extract of Tulbaghia violacea.

Pro-apoptotic glucopyranosides — D-fructofuranose-β(2→6)-methyl-α-D-glucopyranoside and β-D-fructofuranosyl-(2→6)-α-D-glucopyranoside — were uncovered from aqueous whole plant extracts of T. violacea using bioactivity-guided purification. These compounds have structural similarity with the earlier reported methyl-α-D-glucopyranoside from the same herb, which selectively kills cancer cells through apoptosis mechanisms.

All 10 tested phytochemical classes were detected across six solvents applied to fruits and seeds, with more phytochemicals detected in the fruits. The fruit had higher phenolic content across the solvents except in methanol. Conversely, except in hexanoic extracts, the seed had higher total proanthocyanidin contents across the solvents.

3.5 Mechanism of Sulfur Compound Formation

When Tulbaghia tissue is disrupted, a C-S lyase present in cell vacuoles comes into contact with marasmin and catalyzes its breakdown into the thiosulfinate marasmicin (2,4,5,7-tetrathiaoctan-4-oxide), analogously to the formation of allicin from alliin in garlic. It is widely accepted that the distinct garlic-like odor and the specific taste derive from sulfur-containing secondary metabolites, which are typical for both Tulbaghia and Allium.

4. Scientific Evidence by Area of Use

4.1 Antimicrobial Activity

Overview: Compiled data indicate efficacy in several in vitro and in vivo pharmacological properties such as antimicrobial, anti-hypertensive, antioxidant, and anti-cancer activities. All antimicrobial evidence to date is from in vitro or laboratory-based studies; no clinical trials in humans have been conducted for this indication.

Antibacterial: The antimicrobial properties of crude methanol extracts of above- and below-soil parts of T. violacea were quantified by means of an agar diffusion method against 6 plant pathogenic bacteria and 7 fungi. The growth of 3 out of the 6 bacteria — Clavibacter michiganensis, Ralstonia solanacearum, and Xanthomonas campestris — was significantly inhibited by crude extracts of both below-soil and aerial parts of T. violacea, whereas the growth of Pseudomonas syringae, Erwinia carotovora, and Agrobacterium tumefaciens was unaffected.

In a study comparing T. violacea (TV) and Allium ursinum (AU) dichloromethane extracts, the extracts exhibited weak and unspecific antibacterial and antifungal activity. A. ursinum extract was more effective against methicillin-resistant Staphylococcus aureus (MRSA) than TV with an MIC of 80 µg/mL. AU and TV extracts completely inhibited visible growth of B. subtilis at an MIC of 80 and 40 µg/mL, respectively.

T. violacea fruit and seed extracts showed antibacterial activity against Escherichia coli, Staphylococcus aureus, and Enterococcus faecalis, but this activity was dose-dependent. Neither the fruit nor the seed extract had any antibacterial effect on Klebsiella pneumoniae.

Antifungal: Tulbaghia violacea exhibits antifungal activity towards Candida, Aspergillus flavus, and Aspergillus parasiticus. One study aimed to ascertain the effect of T. violacea rhizome extracts on ergosterol production in A. flavus. The MIC of a T. violacea rhizome extract against A. flavus was determined to be 15 mg/ml.

Both the aerial and below-soil extracts of T. violacea significantly inhibited the mycelial growth of 6 of the 7 test fungi — Botrytis cinerea, Sclerotium rolfsii, Rhizoctonia solani, Mycosphaerella pinodes, Botryosphaeria dothidea, and P. ultimum — whereas only the below-soil extract inhibited the mycelial growth of Fusarium oxysporum significantly.

Anti-parasitic: One study investigated the mode of anti-parasitic activity of T. violacea and Allium ursinum dichloromethane extracts against Trypanosoma brucei brucei and Leishmania tarentolae and evaluated their cytotoxic potential against human cells. Both extracts showed a relevant trypanocidal and leishmanicidal activity, although L. tarentolae was less sensitive. The probable mode of action of both extracts was the irreversible inhibition of the activity of Trypanosoma brucei trypanothione reductase enzyme.

Evidence strength: Antimicrobial evidence is exclusively in vitro and in some cases pertains to plant pathogens rather than human pathogens. Results for human pathogenic bacteria are mixed, with some studies describing activity as weak and unspecific. No human or animal trials have been performed. Evidence is preliminary.

4.2 Antihypertensive and Cardiovascular Effects

Overview: This is among the most extensively studied areas for T. violacea, though all evidence remains from animal models. No human clinical trials have been published.

Blood pressure — spontaneously hypertensive rat model: In a study using anaesthetized male spontaneously hypertensive Wistar rats, methanol leaf extract (MLE) of T. violacea at doses of 5–150 mg/kg was infused intravenously. T. violacea significantly (p<0.01) reduced systolic, diastolic, and mean arterial blood pressure, and heart rate, dose-dependently. The hypertensive effect of angiotensin I and the heart rate-increasing effect of dobutamine were significantly (p<0.01) decreased by co-infusion with T. violacea (60 mg/kg). The study concluded that T. violacea reduced blood pressure and heart rate in the spontaneously hypertensive rat, with the reduction in blood pressure possibly due to actions of the MLE on the angiotensin I converting enzyme (ACE) and β₁-adrenoceptors.

Blood pressure — Dahl salt-sensitive (DSS) rat model: In a study using DSS rats, animals were treated intraperitoneally with either distilled water (control), captopril (25 mg/kg), or methanolic extract of T. violacea (TVL) (50 mg/kg) for 7 weeks. This study showed that TVL possesses antihypertensive effects in Dahl salt-sensitive rats when administered over the long-term.

Mechanism — muscarinic receptors and aldosterone: Stimulation of the muscarinic receptors and a reduction in plasma aldosterone levels contribute to the antihypertensive effect of T. violacea.

Atherosclerosis model: The protective effect of T. violacea rhizomes (TVR) against derangements in serum lipid profile, tissue antioxidant enzyme depletion, endothelium dysfunction, and histopathological changes in the aorta and liver of rats fed with an atherogenic diet (4% cholesterol, 1% cholic acid, and 0.5% thiouracil) was investigated. Co-treatment with TVR extracts (250 and 500 mg/kg body weight for two weeks) significantly (p<0.05) protected against elevated serum triglyceride, total cholesterol, LDL-cholesterol, VLDL-cholesterol, and decreased HDL-cholesterol in a dose-dependent manner. The extracts also reduced elevated lipid peroxidation markers and reversed endothelial dysfunction parameters and tissue antioxidant enzyme activities to near normal.

Evidence strength: All cardiovascular evidence is from rodent models (spontaneously hypertensive Wistar rats, Dahl salt-sensitive rats, and diet-induced atherosclerosis models). No clinical trials in humans exist. Evidence is preliminary and cannot be translated to human recommendations.

4.3 Antithrombotic and Antiplatelet Activity

Plant extracts of T. violacea have been investigated for their potential therapeutic effects in the management of various ailments, among which are cardiovascular diseases, due to the wide range of phytocompounds the plant possesses.

An in vitro study investigated the antithrombotic and anticoagulant properties of T. violacea. The bulb and leaf extracts showed antithrombotic activities which were higher than those found in garlic. The IC₂₀₀ values for the leaf and bulb extracts were 0.4 and 0.3 mg/ml, respectively, for the thrombin time (TT) assay. The IC₅₀ value was 1.73 mg/ml for the bulb extract.

In a further in vitro evaluation, a 0.1 mg/ml T. violacea extract mixed with blood plasma demonstrated the lowest platelet adhesion and activation and also reduced whole blood clotting kinetics. There was a reduction of about 70% in platelet adhesion for the 0.1 mg/ml treatment compared to the control in the first 15 minutes, supported by morphological characterization under SEM. These observations suggest that T. violacea may be a potential antiplatelet therapeutic agent to inhibit the initial step of platelet adhesion and ultimately reduce the incidence of cardiovascular events.

Evidence strength: Entirely in vitro. No animal or human studies have directly assessed antithrombotic efficacy in vivo. Evidence is preliminary.

4.4 Antidiabetic and Hypolipidemic Activity

A study was designed to examine the effects of T. violacea methanolic extract on blood glucose, serum lipids, and antioxidative status in streptozotocin-induced diabetic rats. This study examined the effect of T. violacea rhizome methanolic extract on blood glucose and lipids in normal and streptozotocin-induced diabetic rats. Male Wistar rats (250–300 g) were injected intraperitoneally with streptozotocin (60 mg/kg body weight) to induce diabetes, with treatment at TVL 60 mg/kg body weight.

T. violacea has been shown to have antihypertensive as well as antioxidant effects in various rat models. It also showed increased antioxidant activity and decreased lipid peroxidation in rats fed T. violacea methanolic extracts.

Evidence strength: All antidiabetic and hypolipidemic evidence is from animal (rodent) models using induced diabetes. No human clinical trials have been conducted. Evidence is preliminary and is restricted to preclinical data.

4.5 Antioxidant Activity

Multiple studies have demonstrated that extracts of Tulbaghia have marked antioxidant activity as assessed using different assays in vitro including Trolox equivalent antioxidant capacity (TEAC; ABTS assay), ferric-reducing antioxidant power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods.

Acetone and water extracts of T. violacea exhibited antioxidant activity in a concentration-dependent manner across standard assays. Plant polyphenols have been identified as natural sources of antiplatelet and antithrombotic agents. Aside from their well-known antioxidative properties, polyphenols have the ability to inhibit enzymes by regulating different pathways underlying cardiovascular disease, as well as extracellular matrix degradation, inflammatory response, and cell death.

Evidence strength: Antioxidant activity has been reproducibly demonstrated across multiple in vitro assay systems. No human trials have assessed antioxidant outcomes in vivo. Evidence is mechanistic and laboratory-based only.

4.6 Anticancer Activity

Overview: Several studies have previously demonstrated the cytotoxic activities of extracts of T. violacea (wild garlic from Southern Africa) in cancer cells. All evidence is from in vitro cell line studies; no animal or human cancer trials exist for this plant.

Human cancer cell lines — leaf and bulb: Investigating the potential anti-cancer properties of infusions of T. violacea, a panel of four cancer cell lines (HepG2, MCF7, H157, and HT29) and one non-cancerous cell line (KMST6) was treated with leaf and bulb extracts. The extracts were investigated for their effects on cell growth, induction of apoptosis, oxidative stress, and activation of caspase-3. Extracts of the leaves — but not the bulbs — had growth inhibitory effects through induction of apoptosis, associated with the production of reactive oxygen species (ROS) and the activation of caspase-3. This study confirmed that infusions of T. violacea have potential anti-cancer activity and that this bioactivity is contained in the leaf extract, lending support to claims that this plant can be used to treat cancer.

Oral cancer cells: Acetone and water extracts inhibited the growth of the KB (human oral cancer) cell line with IC₅₀ values of 0.2 mg/mL and 1 mg/mL, respectively. Morphological changes such as cell shrinkage, rounding, and formation of membrane blebs were observed in treated cells. The number of apoptotic cells increased as the concentration of the extracts increased. The activation of multi-caspase activity in KB cells treated with T. violacea extracts was concentration-dependent, leading to cell death by apoptosis and cell cycle arrest at the G2/M phase.

Triple-negative breast cancer: T. violacea extracts demonstrated cytotoxic activity against MDA-MB-231 (triple-negative breast cancer), with an IC₅₀ of 300 µg/mL. Additionally, extracts inhibited migration of the cancer cell lines (metastasis).

Pancreatic cancer: Antineoplastic properties of T. violacea were further observed against pancreatic cancer, with 63% inhibition of cell proliferation at a concentration of 250 µg/mL.

Mechanisms of apoptosis induction: All three extract types (hexane, methanol, and aqueous) exhibited anticancer activity, with the most cytotoxic being methanol extract. p53 expression was significantly increased in treated cells, correlating with increased caspase activity. The results point to possible activation of apoptosis following treatment with hexane extracts.

The anticancer activity of T. violacea extracts can be attributed to secondary metabolites such as phenolic compounds, which have been shown to inhibit the formation of tumours by interfering with growth, proliferation, and metastasis, as well as exerting pro-apoptotic effects by blocking proteasome activity and suppressing angiogenesis.

Evidence strength: All anticancer evidence is from in vitro cell culture experiments. These studies demonstrate plausible mechanisms (apoptosis induction, caspase activation, p53 upregulation) but cannot be used to draw conclusions about therapeutic efficacy in humans. Evidence is preliminary.

4.7 Androgenic / Reproductive Effects

Treatment of testicular cells with T. violacea (312.5–5000 µg/ml) significantly increased (p<0.05) LH-induced testosterone production as compared to vehicle-treated control, whereas cells without LH-treatment showed no significant change in testosterone concentrations. The data presented shows that T. violacea has androgenic properties, though further studies are warranted to determine and clarify the exact mechanisms involved. The ethanol extract significantly increased LH-induced testosterone production without having any significant effect on cell viability.

Evidence strength: A single in vitro study using testicular cell cultures. No in vivo animal studies or human trials exist for this indication. Evidence is very preliminary.

4.8 Tuberculostatic Activity

Marasmicin has attracted considerable attention because of its antifungal and tuberculostatic activities. The link to tuberculosis treatment is both traditional and supported by the identification of tuberculostatic activity in the principal secondary metabolite. However, no clinical or in vivo animal studies have been published establishing therapeutic efficacy against tuberculosis in a living system.

5. Body Systems and Health Areas Associated with Tulbaghia

Cardiovascular system: antihypertensive, antithrombotic, antiplatelet, and hypolipidemic effects, studied in animal models
Immune and infectious disease: antibacterial, antifungal, anti-parasitic (trypanocidal, leishmanicidal), and potential tuberculostatic activity, studied in vitro
Metabolic system: antidiabetic and lipid-lowering effects in animal models of streptozotocin-induced diabetes
Oncology: cytotoxic and pro-apoptotic activity across multiple human cancer cell lines (breast, oral, pancreatic, hepatic, lung), studied in vitro
Antioxidant / redox biology: radical-scavenging activity demonstrated in multiple in vitro assay systems
Reproductive / endocrine system: androgenic activity (LH-potentiated testosterone secretion) shown in testicular cell cultures in vitro
Respiratory system: traditional use for asthma, tuberculosis, and colds; limited laboratory support for tuberculostatic activity of marasmicin
Gastrointestinal system: traditional use for stomach problems, intestinal worms; anthelmintic activity noted in ethnobotanical surveys

6. Dosage Forms and Dosages Reported in Studies

No established human dosage exists for Tulbaghia violacea in any regulatory or pharmacopoeial monograph. The following dosages appear solely in preclinical research and are reported only as stated in published sources.

Antihypertensive study (spontaneously hypertensive rats, IV administration): Methanol leaf extract (MLE) of T. violacea at doses of 5–150 mg/kg was infused intravenously in anaesthetized male spontaneously hypertensive rats.
Antihypertensive study (Dahl salt-sensitive rats, intraperitoneal): DSS rats were treated intraperitoneally with methanolic extract of T. violacea (TVL) at 50 mg/kg body weight for 7 weeks, alongside captopril (25 mg/kg) as a positive control.
Antidiabetic/metabolic study (rats, intraperitoneal): In a streptozotocin-induced diabetic rat model, animals received TVL at 60 mg/kg body weight; the metformin comparator dose was 250 mg/kg body weight.
Atherosclerosis model (rats, oral): TVR extracts were administered at 250 and 500 mg/kg body weight for two weeks.
Androgenic study (in vitro, testicular cell cultures): Cells were treated with T. violacea extract concentrations ranging from 312.5 to 5000 µg/ml.
Antithrombotic study (in vitro): A concentration of 0.1 mg/ml of aqueous T. violacea extract mixed with blood plasma demonstrated the lowest platelet adhesion and activation.
Antiplatelet/anticoagulant study (in vitro): IC₂₀₀ values for the leaf and bulb extracts were 0.4 and 0.3 mg/ml, respectively, for the thrombin time assay. The IC₅₀ value was 1.73 mg/ml for the bulb extract.
Oral cancer cells (in vitro): Extracts inhibited the growth of the KB cell line with IC₅₀ values of 0.2 mg/mL (acetone) and 1 mg/mL (water).
Antifungal MIC (marasmicin vs. allicin comparison): Antimicrobial activity of marasmicin was evaluated at MIC 4–64 µg/ml compared with allicin at MIC 4–32 µg/ml.

7. Safety Considerations and Toxicology

7.1 Preclinical Toxicity Studies

The methanolic extract of the rhizome of T. violacea was tested for toxicity in albino Wistar rats. A single oral administration of a 5 g/kg dosage of the extract did not produce mortality or significant behavioral changes during 14 days of observation. In the sub-chronic study, the extract administered daily for a period of 28 days showed no mortality or morbidity, and relative weights of organs were not affected. The results suggest that the rhizomes of T. violacea may be potentially safe for consumption, with no significant effect on markers of kidney function or hematological parameters in the rats. Indicators of liver damage such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as total serum protein and albumin, showed no significant alteration in the extract-treated animals when compared with controls at all doses used.

7.2 Conflicting Evidence on Cytotoxicity

There is contradictory evidence regarding the safety and toxicity of the plant. Certain extracts exhibit toxicity at higher concentrations. Water extracts from stems demonstrate genotoxic effects, while ethanol extracts cause significant cellular damage and inhibit macrophage proliferation, classifying them as highly cytotoxic. The essential oil has an LC₅₀ of 12.59 µg/mL against brine shrimp, indicating toxicity.

7.3 Traditional Safety Reports

Some fatalities and symptoms like gastro-enteritis, abdominal pain, cessation of gastro-intestinal peristalsis, sloughing of the intestinal mucosa, and contraction of the pupils have been implicated in medication prepared with T. violacea. These reports arise from ethnobotanical documentation and are not verified in controlled studies, but they underscore the importance of dosage and preparation method.

7.4 Conservation and Harvesting Concerns

Due to increasing evidence of its potential as an antifungal agent, large-scale commercialization is anticipated. However, this may make the Tulbaghia genus threatened, as it is susceptible to overuse. The increasing high usage — especially of the underground organs — as well as the incessant reliance on wild populations, will eventually affect their abundance and possibly make them susceptible to extinction.

7.5 Potential Drug Interactions

Given its demonstrated in vitro antiplatelet and anticoagulant activity — with T. violacea showing antithrombotic activities higher than those found in garlic in in vitro assays — there is a theoretical concern that concurrent use with anticoagulant or antiplatelet drugs (e.g., warfarin, aspirin, clopidogrel) could potentiate bleeding risk. This has not been formally studied. Similarly, based on demonstrated antihypertensive effects in animal models involving ACE inhibition and β₁-adrenoceptor activity, additive effects with antihypertensive medications are a plausible, though unstudied, concern.

7.6 Absence of Human Safety Data

No controlled human clinical trials have evaluated the safety, tolerability, adverse effect profile, or drug interactions of T. violacea supplementation. The plant is used as a food ingredient in South Africa, and its leaves and flowers are considered edible in culinary quantities, but formal safety evaluation in the context of supplemental or therapeutic dosing has not been conducted in humans.

7.7 Knowledge Gaps

Despite the extensive in vitro pharmacological screening of extracts of Tulbaghia, less effort has been made to isolate and identify their active principles. Hence, the phytochemistry of the genus Tulbaghia largely remains understudied.

References

Health Conditions

Health conditions that Tulbaghia may help support.

No conditions available.

Body Systems

Body systems that Tulbaghia may help support.

No body systems available.