Montanoa tomentosa

Montanoa tomentosa (Zoapatle / Cihuapatli)

1. Identity and Botanical Description

Montanoa tomentosa Cerv. is the accepted scientific name for a species of flowering plant belonging to the family Asteraceae (tribe Heliantheae). It is a shrub originally from Mexico and Central America, known for its medicinal properties. The zoapatle plant is a bush about 2 m high that grows wild in Mexico. It is native to Mexico and much of Central America.

This small yellow-flowered shrub is best known for its use in traditional herbal medicine. The plant belongs to the same genus as several closely related medicinal species, including Montanoa frutescens and Montanoa grandiflora.

Common Names and Synonyms

• Zoapatle — the local common name in Mexico.
• Cihuapatli — from the Nahuatl language, meaning "women's medicine" (cihuatl = woman, patli = remedy or medicine).
• Zoapatli — a variant Nahuatl spelling that Spanish pronunciation later transformed into "zoapatle."

The Cihuapatli Group

Cihuapatli is the common name assigned to plants from the Montanoa genus (family: Asteraceae; tribe: Heliantheae), including Montanoa tomentosa, Montanoa frutescens, and Montanoa grandiflora, among others. While this article focuses on M. tomentosa, the three species have historically been used interchangeably, and much of the pharmacological research covers the genus collectively.

Natural Source and Common Preparations

The extract of leaves was used in women to induce menstruation, abortion, and labor, and also to reduce postpartum bleeding. The leaves are also used for their diuretic properties and the ground roots are used in the treatment of dysentery.

The plant has been used for centuries in the form of a "tea" or other crude aqueous preparations primarily as a labor inducer or menses inducer for humans. Modern research preparations include aqueous crude extracts (ACE), lyophilized powders, and purified fractions of the isolated diterpenoids. The ethnomedical use of the tea prepared from the leaves of the zoapatle plant for the induction of menses and labor in the past 400 years in Mexico, the clinical evaluation of this preparation in human volunteers, the isolation, structural elucidation, and biological evaluation of zoapatanol — an oxepane diterpene claimed to be responsible for the action of the tea — as well as the synthesis of zoapatanol analogues and derivatives, have been the subjects of numerous reports.

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2. Traditional and Historical Use

Pre-Columbian and Colonial Era Documentation

Descriptions of this plant as a traditional remedy are found in the Badianus Codex or Libellus de Medicinalibus Indorum Herbis (1552), which lists botanical determinants, traditional recipes, and prescriptions; the Historia General de las Cosas de Nueva España (Florentine Codex); and Historia Natural de la Nueva España, which describes a tea prepared from the leaves of M. tomentosa that facilitates parturition, ameliorates the puerperium, serves as a contraceptive agent, and remedies mood disorders.

Zoapatle has been used since the 16th century to induce labor or to increase both the tone and frequency of uterine contractions during labor. Since 1866, the plant has been recognized as a potential menses inducer. Pharmacological observations of zoapatle were made in Mexico in 1945 and focused on the administration of zoapatle aqueous crude extract (ZACE).

Peoples and Regions

In ancient Mexican traditional medicine, the Nahuatl-speaking peoples used Cihuapatli for the treatment of mood and nervous disorders. The aqueous crude extract from these plants has been used for centuries in Mexican traditional medicine as a remedy for reproductive impairments and mood disorders.

Traditional Indications

• An extract of the leaves was used to start uterine contractions to induce menstruation, abortion, and labor, and to slow postpartum bleeding.
• M. tomentosa aqueous crude extract has been used for the last five centuries for the induction of labor, regulation of fertility, treatment of postpartum bleeding problems, and to induce menses.
• It was used for the treatment of mood and nervous disorders.
• In Mexico, there is a history of the use of M. tomentosa as a traditional remedy for sexual dysfunction.
• There are reports indicating that this plant was also consumed by Mexican ancient people for its relaxing properties.
• The leaves are also used for their diuretic properties, and the ground roots are used in the treatment of dysentery.

Traditional Preparation

The predominant traditional preparation was a tea or infusion of the leaves. The Historia Natural de la Nueva España describes a tea prepared from the leaves of M. tomentosa that facilitates parturition and ameliorates the puerperium. An aqueous decoction of the dried leaves was the standard folk method of administration.

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3. Phytochemistry: Key Constituents and Active Compounds

More than 70 compounds of the Montanoa genus have been characterized. The most relevant compounds are terpenoids, diterpenoids, monoterpenoids, and sesquiterpenoids, with anxiolytic, antitumor, anti-inflammatory, and antineoplastic properties.

3.1 Oxepane Diterpenoids

The most pharmacologically distinctive class of compounds in M. tomentosa is the oxepane diterpenoids — a structurally unusual group featuring a seven-membered oxygen-containing ring. (+)-Zoapatanol, montanol, tomentanol, and tomentol are diterpenoid oxepanes isolated from the leaves of the Mexican zoapatle plant, Montanoa tomentosa.

• Zoapatanol: The first and most studied oxepane diterpenoid. Zoapatanol is an oxepane diterpene claimed to be responsible for the action of the tea. Recent studies support the belief that zoapatanol and its metabolites might be responsible for the observed antifertility activity.
• Montanol: A related oxepane diterpenoid co-isolated with zoapatanol.
• Tomentanol and Tomentol: The leaves of Montanoa tomentosa afforded a new oxepane diterpene, tomentanol, and its previously known relatives zoapatanol, montanol, tomexanthin, and tomentol.
• Chemical analysis of Montanoa tomentosa yielded, in addition to the known biologically active oxepane diterpenoids zoapatanol, tomentol, and tomexanthol, three new uterotonic acyclic diterpenoids, which are considered the precursors of the oxepane derivatives mentioned above.

3.2 Kaurane-Type (Tetracyclic) Diterpenoids

The bioactive molecules are the uterotonic diterpenes kaurenoic acid (KA), grandiflorenic acid (GF), and monoginoic acid (MO). Roots of M. tomentosa contain all three diterpenes, whereas in leaves only kaurenoic acid and grandiflorenic acid are present.

• Kaurenoic acid (ent-kaur-16-en-19-oic acid): A tetracyclic diterpene with established uterotonic and, according to some research, anti-inflammatory properties.
• Grandiflorenic acid (kauradienoic acid): The aqueous crude extract of Montanoa tomentosa leaves produced different (or even opposite) effects on uterine motility during distinct phases of the oestrus cycle in the rat. Furthermore, pure grandiflorenic acid (GA), obtained from the phytochemical workup of this plant, reproduced the uterine responses induced by ZACE.
• Monoginoic acid: Present in roots; another uterotonic tetracyclic diterpene.
• Three tetracyclic diterpenes (kaurenoic, kauradienoic, and monoginoic acid) have been isolated with different activities, among which are uterotonic, antispasmodic, antineoplastic, antibacterial/antifungal, and anti-inflammatory effects.

3.3 Sesquiterpene Lactones

Investigation of the leaves of Montanoa tomentosa ssp. microcephala resulted in the isolation of three novel guaianolide sesquiterpenes — montacephalin (1), tomencephalin (2), and 5-hydroxytomencephalin (3) — which were shown to be cytotoxic (P-388). Additional sesquiterpene lactones characterized include zoapatanolide A and pumilin.

3.4 Triterpenes and Sterols

From the hexane extract (MtHex) of M. tomentosa, the following compounds were isolated and identified: β-sitosterol (1), stigmasterol (2), kaurenoic acid (3), grandiflorenic acid (4), taraxasterol (5), and 15-cinnamoylkaurenic acid (6). Also isolated were the known terpenes β-amyrin, β-amyrin acetate, stigmasterol, stigmasterol-3β-D-glucoside, (−)-kaur-16-en-19-oic acid, and monoginoic acid.

It has been described that Montanoa contains triterpenoids with anti-tuberculosis, anti-fungal, anti-inflammatory, and anti-viral activity.

3.5 Flavonoids

Phytochemical studies have revealed that Montanoa tomentosa contains several classes of chemical constituents including flavonoids and terpenoids. The flavonoids nicotiflorin (kaempferol-3-rutinoside) and isoquercitrin have been isolated from the leaves.

3.6 Volatile Oil Constituents

The constituents of the volatile oils of Montanoa tomentosa were investigated using capillary GC/MS. Borneol acetate, beta-cubebene, and beta-caryophyllene were found to be the major constituents of the volatile oil of M. tomentosa. The possible correlation between the high concentration of monoterpenes and the alleged antifertility effect of the plant is discussed in the literature.

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4. Mechanisms of Action

4.1 Uterotonic / Oxytocic Activity

Data show that the cihuapatli extract acts directly at the spinal system in charge of the expression of ejaculatory motor patterns and suggest that the aqueous crude extract exerts its aphrodisiac properties by increasing sexual potency acting as an oxytocic agent.

The aqueous crude extract of Montanoa tomentosa leaves produced different — or even opposite — effects on uterine motility during distinct phases of the oestrous cycle in the rat. This bidirectional effect on uterine smooth muscle has been attributed to the hormonal environment. The action of zoapatle is discussed in relation to hormonal stage and to a probable adrenergic mechanism involved.

With respect to smooth muscle action, compounds in zoapatle exert their impact on uterine muscle through the direct stimulation of β-adrenergic receptors and/or cholinergic receptors in the smooth muscle cell membrane. However, the exact receptor of this pathway in which Montanoa tomentosa acts is still unknown.

The kaurane-type diterpenes display a more complex profile: grandifloric and kauradienoic acid from M. tomentosa were assayed on contractions of rat uterus induced by acetylcholine, oxytocin, and serotonin. The four kauranes assayed inhibited the contractile activity induced by the three agonists through a mechanism independent of either β₂-adrenergic or H₂-histaminergic receptors present in uterine smooth muscle.

4.2 Oxytocinergic System Modulation

The release of oxytocin (OXT) can be promoted by neurosteroids, oxytocin analogues, and oxytocin-receptor ligands produced by some plants. In pre-clinical research, both the extract and some of its active metabolites have produced oxytocinergic-like effects on female reproductive organs.

An M. tomentosa infusion promoted an anti-depressant-like effect in rats on the FST while simultaneously inducing activation of hypothalamic oxytocinergic neurons in both experimental and control rats, suggesting that the biologically-active compounds that it contains may act directly on the oxytocinergic system in the brain.

The cihuapatli-induced ejaculatory motor patterns were similar to those obtained after systemic oxytocin. Cihuapatli- and oxytocin-induced ejaculatory motor responses and penile erections and movements were abolished by the pre-treatment with hexamethonium, a selective oxytocin antagonist.

4.3 GABAergic System (GABA_A Receptor)

Studies have shown that Montanoa has anxiolytic properties. The mechanism underlying this action lies in the interaction with the GABA_A receptor. Phytochemical studies have revealed that Montanoa tomentosa contains several classes of chemical constituents including flavonoids and terpenoids. It is well recognized that many of these compounds produce anxiolytic-like effects which are mainly dependent on their interaction with the GABA_A receptor complex.

Pentacyclic triterpenes and tetracyclic diterpenes (e.g., ent-kaurenoic acid, grandiflorenic acid, kauradienoic acid, zoapatanol, and montanol), sesquiterpene lactones, and flavonoids are the main biologically active compounds identified in plants from the Montanoa genus. With respect to the anxiolytic-like effect, it is possible that terpenes or flavonoids could be involved, considering that these kinds of compounds have the capacity to target the GABAergic system through activation of GABA_A receptors.

4.4 Blood–Brain Barrier Penetration

Recent studies reported that the extract of Cihuapatli prepared with Montanoa tomentosa can cross the blood–brain barrier to exert its actions directly on the central nervous system.

4.5 NF-κB Inhibition

Certain components of the Montanoa genus, including Zoapatle, may contribute to inhibitory activity against NF-κB, a key player in the inflammatory cascade. In contrast, kaurane-type diterpenes inhibit the contractility and induce the relaxation of smooth muscle.

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5. Scientific Evidence by Area of Use

5.1 Reproductive Effects: Uterotonic, Labor Induction, and Contraception

Human/Clinical Evidence

The most significant piece of human clinical data is a small study published in 1979. Freshly prepared aqueous decocts of the Mexican plant Montanoa tomentosa were administered orally to six women in the early stages of pregnancy for two days prior to interruption of gestation by vacuum aspiration. The daily dose administered varied between 1.0 and 1.4 gm-equivalent of dry leaves per kilogram of body weight. A comparable control group of six pregnant women received the same volume of commercial tea according to the same schedule before vacuum aspiration.

The results of this human study showed uterotonic activity: administration of Zoapatle extracts resulted in a menstrual-like cramp and a significant dilatation of the cervix in all subjects studied. In four of the six subjects the menstrual-like pains were associated with bleeding. No comparable effects were observed in the control group.

Evidence strength: This single study had an extremely small sample size (n = 6 per group) and no placebo-controlled blinding. It demonstrates a uterotonic effect in vivo in humans at the doses tested, but the data cannot support dose-response conclusions or broader clinical application.

Preclinical Evidence

As the purity of the extracts increased, it was possible to demonstrate inhibition of implantation in rats and mice when administered on days 1–6 and in hamsters when administered on days 4–6 of gestation. However, when an aqueous extract of the leaves similar to the tea utilized in folklore medicine was administered orally during early stages of pregnancy, no antifertility activity could be detected in standard rodent models, with purer fractions being required. Purer fractions derived from the plant were more potent in the assay system when administered either intraperitoneally or orally.

The experimental studies with cihuapatli aqueous crude extract or its purified fractions confirm popular observations, and it has been shown that the contraceptive effects of Montanoa tomentosa aqueous crude extract are provoked by inhibition of implantation, cervical dilation, and uterine bleeding without influencing endocrine status.

Evidence strength: Preclinical evidence is consistent and reproduced across multiple laboratories, but no adequately powered controlled clinical trial has been conducted on contraceptive or labor-induction endpoints.

5.2 Aphrodisiac and Pro-Sexual Effects

Preclinical Evidence

Results showed that acute oral administration of crude extracts of M. tomentosa facilitates expression of sexual behavior in sexually active male rats, significantly increases mounting behavior in genitally anesthetized animals, and induces the expression of sexual behavior in non-copulating male rats. Altogether, these data reveal a facilitatory action of this extract on sexual activity and particularly on sexual arousal. Present findings provide experimental evidence that the crude extract preparation of M. tomentosa, used as a traditional remedy, possesses aphrodisiac properties.

Systemic administration of the aqueous crude extracts of Montanoa tomentosa exerted a pro-ejaculatory effect and produced an increase in the number of discharges in the ejaculatory motor patterns in spinal rats. The cihuapatli-induced ejaculatory responses included the expression of penile erections and penile movements and the potent expulsion of urethral contents.

Two studies conducted in rats demonstrated the aphrodisiac properties of Montanoa tomentosa. This activity has been attributed to the presence of components that act as oxytocic agents.

Evidence strength: All evidence for aphrodisiac activity is preclinical (animal models only). No controlled human trials have been conducted. The mechanistic link to the oxytocinergic system is biologically plausible, but translation to humans is unestablished.

5.3 Anxiolytic Effects

Preclinical Evidence

Multiple independent preclinical studies have evaluated the anxiolytic properties of M. tomentosa:

The effect of Montanoa tomentosa lyophilisate (MT) on rats' anxiety-like behavior was evaluated and its mechanism of action analyzed. The anxiolytic-like action of MT (1.5, 3.0, 6.0, and 12.0 mg/kg) was investigated in male Wistar rats tested in three animal models of anxiety: the burying behavior, the elevated plus maze, and the hole-board tests. The results corroborate the anxiolytic-like actions of Montanoa tomentosa and suggest that this effect is mediated through GABA_A receptors but not oxytocin receptors.

The effect was also examined in females under varying hormonal conditions: MT reduced anxiety-like behavior in female rats under progesterone withdrawal, in contrast to diazepam which was ineffective. MT's anxiolytic-like effect was blocked by picrotoxin, suggesting the participation of the GABA_A receptor complex. However, increased anxiety-like behavior was observed in rats with a high hormone level condition and low doses of MT. Beneficial anxiolytic-like actions of MT are observed under low hormone conditions, particularly in the progesterone withdrawal challenge.

Evidence strength: Consistently demonstrated across multiple animal models and study groups. The GABA_A/benzodiazepine receptor mechanism is well-supported. However, all data are preclinical; no human studies exist. Importantly, the hormonal context of the animal appears to modulate outcomes, which is a relevant complication for potential human application.

5.4 Antidepressant-Like (Anti-Despair) Effects

Preclinical Evidence

The aim of one study was to analyze the behavioral effects of acute administration of a Mt infusion on male rats during the Open Field (OFT) and Forced Swim (FST) Tests, and their association with the activation of oxytocin (OXT) cells in the paraventricular and supraoptic nuclei. Fifty-two adult male Wistar rats were assigned to two conditions. Each integrated condition included four groups [Control, Vehicle, Fluoxetine (Flx; 10 mg/kg), and Mt (50 mg/kg), p.o.]. Mt and Flx treatment produced an anti-despair-like effect on the FST.

The three Montanoa species produce anxiolytic-like and antidepressant-like effects in both male and female rats in preclinical studies.

Montanoa extracts reduced immobility since day 1 of treatment, while fluoxetine and Remotiv required 14 days. GABA_A antagonism blocked the effects of Montanoa extracts, but not of fluoxetine or Remotiv. Montanoa extracts prevented quickly the stress-induced behaviors in the swimming test through action at the GABA_A receptor, exerting a protective effect different from the typical antidepressants.

Evidence strength: Preclinical evidence only. The faster onset of action compared to fluoxetine in FST models is intriguing but these behavioral tests do not directly translate to clinical antidepressant efficacy in humans. No human data exist.

5.5 Anti-Inflammatory Activity

Preclinical / In Vitro Evidence

M. tomentosa has been used in Mexican traditional medicine as a labor inducer and contraceptive, as well as for the treatment of pain after childbirth. In this sense, M. tomentosa is an important source of metabolites with potent anti-inflammatory activity.

The MtHex (1 mg/ear) reduced edema (61.16 ± 3.8%), showing a similar effect to indomethacin (70.02 ± 1.24%) in the TPA-induced ear edema model in mice. From the hexane extract, compounds isolated and identified were: β-sitosterol, stigmasterol, kaurenoic acid, grandiflorenic acid, taraxasterol, and 15-cinnamoylkaurenic acid. Compound 6 (15-cinnamoylkaurenic acid) showed the most significant effect in the TPA model (79.05 ± 3.07%). These exploratory results demonstrate that M. tomentosa could be an important source of terpene-type metabolites such as kaurenoic acid derivatives and sterols with potential anti-inflammatory effects.

Evidence strength: Preliminary; mouse ear edema model only. No human clinical trials on inflammatory endpoints have been conducted.

5.6 Cardiac Hypertrophy and Inflammatory Markers

Preclinical Evidence

A 2024 murine study evaluated the effect of Zoapatle on inflammatory markers in a model of ventricular hypertrophy. The aim was to evaluate the effect of Zoapatle on the hypertrophy index and the gene expression of TNF-α, IL-1β, NF-κB, STAT5, and the PRLR in the brain, left ventricle, and renal cortex of rats with isoproterenol-induced cardiac hypertrophy. Three groups were studied: the control group (n = 4), hypertrophy group (n = 4), and hypertrophy group treated with Zoapatle (n = 4). Zoapatle was administered for 28 consecutive days (25 mg/kg).

A notably reduced left ventricle mass index was observed in the Zoapatle group. Additionally, Zoapatle administration in cardiac hypertrophy demonstrated a significant decrease in the gene expression of TNF-α, IL-1B, STAT5, and the PRLR. TNF-α and the transcription factor STAT5 exhibited a similar trend in both the left ventricle and renal cortex, suggesting a correlation with the inflammatory state in these tissues due to ventricular hypertrophy. The findings suggest that Zoapatle reverses the hypertrophy index in a hypertrophy model, concurrently reducing several proinflammatory mediators associated with the hypertrophy index.

Evidence strength: Very preliminary; small sample sizes (n = 4 per group), single animal model. Results are hypothesis-generating only.

5.7 Antitubercular Activity

It has been described that Montanoa contains triterpenoids with anti-tuberculosis activity. This is based on work identifying antitubercular activity of triterpenoids from Asteraceae flowers, which include the genus Montanoa. Evidence is limited to in vitro and early-stage preclinical work.

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6. Body Systems and Health Areas of Association

• Female Reproductive System: Uterotonic activity, labor induction, menses regulation, postpartum hemorrhage, contraception (via anti-implantation), and dysmenorrhea. This is the most historically and scientifically documented area.
• Male Reproductive / Sexual Function: Aphrodisiac and pro-ejaculatory effects mediated through the oxytocinergic system, demonstrated in multiple preclinical studies.
• Central Nervous System — Anxiety: GABA_A/benzodiazepine receptor-mediated anxiolytic effects, demonstrated in validated animal models; shows hormonal state-dependency in females.
• Central Nervous System — Mood: Anti-despair-like (antidepressant-type) effects in rodent forced swim test, linked to activation of hypothalamic oxytocinergic neurons.
• Musculoskeletal / Smooth Muscle: Smooth muscle relaxation via kaurane-type diterpenes.
• Inflammatory Pathways: Anti-inflammatory activity via terpenoids (kaurenoic acid derivatives), with putative NF-κB inhibition.
• Cardiovascular System: Preliminary evidence from animal models of ventricular hypertrophy, with reductions in pro-inflammatory markers.
• Urinary / Renal System: Traditional diuretic use; preliminary gene expression evidence from kidney tissue in the hypertrophy model.
• Gastrointestinal System: Traditional use of ground roots for dysentery.

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7. Dosage Forms and Reported Dosages

There is no standardized pharmaceutical-grade dosage for M. tomentosa. Dosages reported in the scientific literature are as follows:

7.1 Human Studies

• In the only published human clinical study, the daily dose of freshly prepared aqueous decoct administered varied between 1.0 and 1.4 gm-equivalent of dry leaves per kilogram of body weight, administered for two days prior to vacuum aspiration in women aged 24–37 of 6–7 weeks' gestation.

7.2 Animal (Preclinical) Studies

• The anxiolytic-like action of MT was investigated at doses of 1.5, 3.0, 6.0, and 12.0 mg/kg in male Wistar rats (lyophilisate, route not specified in available abstracts).
• Fluoxetine (10 mg/kg) and Mt (50 mg/kg), administered p.o., were compared for anti-despair effects in the forced swim test in male Wistar rats.
• In the cardiac hypertrophy study, Zoapatle was administered for 28 consecutive days at 25 mg/kg.
• The anxiolytic-like effect of aqueous crude extract of M. frutescens (25, 50, and 75 mg/kg) was investigated in male Wistar rats evaluated in the elevated plus-maze and compared with several doses of diazepam (1, 2, and 4 mg/kg) as a reference anxiolytic drug.

7.3 Preparation Forms

Preparations used in research and traditional contexts include:

• Aqueous crude extract (ACE / ZACE): The traditional tea/decoction form; most extensively studied in both traditional and scientific contexts.
• Lyophilisate: Freeze-dried extract used in several anxiolytic studies.
• Purified fractions (hexane, ethyl acetate, methanol extracts) and isolated compounds (zoapatanol, grandiflorenic acid, kaurenoic acid): Used primarily in mechanistic and phytochemical research.

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8. Safety Considerations and Interactions

8.1 Human Safety Data

Peroral administration of Zoapatle decocts did not produce any cardiovascular changes, and it did not influence the hematologic status, liver, kidney, and thyroid function, blood lipids, proteins, and electrolyte status in the six women studied at doses of 1.0–1.4 g-equivalent dry leaves/kg body weight for two days.

Based on experimental data, it was concluded that oral administration of Montanoa tomentosa has no toxic effects at the doses tested in those early studies. However, this conclusion derives from very limited human data and cannot be considered comprehensive toxicological evidence.

8.2 Uterotonic and Pregnancy Risk

Mexican traditional medicine mentions that the aqueous crude extract of this plant possesses contraceptive activity in women during the early stages of pregnancy. Experimental studies confirm that the contraceptive effects of Montanoa tomentosa aqueous crude extract are provoked by inhibition of implantation, cervical dilation, and uterine bleeding. This constitutes a serious and well-documented safety concern: the plant has documented abortifacient properties at clinically relevant doses, and any pregnant person should be aware of its historical use specifically to induce abortion and uterine contractions.

8.3 Hormonal-State Dependent Paradoxical Effects

Increased anxiety-like behavior was observed in rats with a high hormone level condition and low doses of MT. Beneficial anxiolytic-like actions of MT are observed under low hormone conditions, particularly in the progesterone withdrawal challenge. Furthermore, the participation of the GABA_A receptor is evidenced. However, hormonal variations could induce the opposite effects, hence women should be cautious.

8.4 Sedative Potential

The results corroborate the use of M. frutescens in folk Mexican ethnomedicine as a potential anxiolytic agent and suggest that this effect is mediated by the GABA_A receptors. Additionally, some sedative effects with high doses of M. frutescens were detected in the present study. By extension, similar sedative potential may apply to M. tomentosa, given the shared mechanism, though this has not been directly confirmed at equivalent doses.

8.5 Cytotoxic Sesquiterpene Lactones

Investigation of the leaves of Montanoa tomentosa ssp. microcephala resulted in the isolation of three novel guaianolide sesquiterpenes — montacephalin, tomencephalin, and 5-hydroxytomencephalin — which were shown to be cytotoxic (P-388) in in vitro tumor cell assays. The relevance of these cytotoxic sesquiterpenes to human safety at typical ingested doses remains unexplored.

8.6 Cardiovascular Interactions

Compounds in Zoapatle exert their impact on uterine muscle through the direct stimulation of β-adrenergic receptors and/or cholinergic receptors in the smooth muscle cell membrane. This modulation is particularly relevant in cardiovascular diseases, in which the adrenergic pathway plays a hegemonic role in physiological cardiac function, mainly in the β₁ receptor. The potential for interactions with cardiovascular drugs acting on adrenergic pathways has not been directly studied.

8.7 Overall Evidence Limitations

As with the entire pharmacological literature on M. tomentosa, safety data are extremely limited. The sole human study enrolled only six individuals and lasted two days, with a specific focus on uterotonic outcomes. There are no long-term human safety studies, no pharmacokinetic studies in humans, and no systematic evaluations of drug–herb interactions. The full toxicological profile of isolated active compounds — particularly the cytotoxic sesquiterpene lactones — at typical or prolonged exposure levels has not been established in humans.

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