Copalchi

Copalchi (Hintonia latiflora): A Comprehensive Reference

1. Identity and Botanical Classification

Copalchi is the common Mexican name for a group of medicinal plants with intensely bitter bark, most prominently Hintonia latiflora (Sessé et Mociño ex DC.) Bullock. The term copalchi has been used in the scientific literature to define a group of plants of the Rubiaceae and Euphorbiaceae families with extremely bitter stem-barks, useful for treating diabetes and malaria. In its strictest and most commercially significant sense, copalchi refers to Hintonia latiflora, but the broader "copalchi complex" encompasses several related species.

1.1 The Copalchi Complex

The copalchi complex, Hintonia latiflora, H. standleyana Bullock and Exostema caribaeum (Jacq.) Roem. et Schult., is widely used in Mexico and includes the main, highly commercialized species that conform the Rubiaceae section of a medicinal plant complex known as the copalchi complex. The definition of the copalchi complex is further complicated by the inclusion of other poorly studied Rubiaceae species such as Coutarea hexandra (Jacq.) K. Schum., Exostema mexicanum A. Gray and Simira mexicana (Bullock) Steyerm., and Euphorbiaceae species, mainly Croton guatemalensis Lotsy, C. glabellus L., C. niveus Jacq. and C. reflexifolius Kunth.

The primary species H. latiflora is a synonym of the historical name Coutarea latiflora DC., and this earlier name appears throughout older German and Mexican pharmacological literature. The plants are collectively branded by consumers with synonyms such as copalchis, copalquín, jutetillo, or campanilla. Additional vernacular names in the Mexican marketplace include palo amargo (bitter stick) and cáscara sagrada.

1.2 Botanical Description and Habitat

The taxonomy of copalchi within the diverse Rubiaceae family — which also includes coffee and quinine-producing species — underscores its botanical significance. The bark of Hintonia latiflora is a crucial identifying feature; it is generally smooth, grayish-brown, and possesses a fine texture that often peels away in thin, elongated strips. This peeling characteristic is especially important for traditional harvesting, as the bark is the primary part utilized for its medicinal properties. Ecologically, copalchi thrives in areas with well-drained soils, often found as an understory component within deciduous forests, benefiting from dappled sunlight and consistent moisture. The stem-bark infusion is highly valued in contemporary Mexico and the plant has a well-documented ethnomedical record comprising more than 400 years.

1.3 Common Forms and Preparations

The medicinally used material is the dried stem bark, also called the cortex. The bark was traditionally brewed into teas or decoctions, which were consumed to address a variety of ailments. The consumption of this medicinal plant is by means of hot infusions or in capsules with extract. Modern commercial forms include dry concentrated bark extracts in capsule form and standardized liquid extracts (drops). One licensed natural health product (NHP) lists Hintonia latiflora as an active ingredient: Sucontral D, which contains a dry extract of H. latiflora bark, with a drug-to-extract ratio (DER) range of 2–4:1 (w/w) and a content of 6% coutareagenin, in combination with biotin, chromium, folate, and other micronutrients. In clinical studies, the capsule formulation used in the Korecova & Hladikova (2014) trial contained 100 mg of a dry concentrate per capsule (DER 2.4:1, solvent 32% ethanol), combined with vitamins C, E, B1, B2, B6, B12, folic acid, biotin, zinc, and chromium.

2. Traditional and Historical Use

2.1 Mesoamerican Origins

The copalchi complex is widely used in Mexico for treating diabetes and gastrointestinal disorders. The first therapeutic use for H. latiflora bark was registered in the Florentine Codex in the sixteenth century. This Franciscan compilation of Aztec (Nahua) knowledge, assembled by Bernardino de Sahagún, thus constitutes the earliest documented evidence of copalchi's medical application. The extremely bitter stem-bark of some Mexican Rubiaceae species, commonly known as "Copalchi," has been used in Mexican traditional medicine for over 400 years with well-documented ethnomedical properties; Hintonia species are widely commercialized under the names copalchi, copalquín, cáscara sagrada, and quina.

2.2 Conditions Treated in Folk Medicine

The stem-barks of Hintonia latiflora and Hintonia standleyana, locally known as "copalchi," are used for treating several maladies such as diabetes and gastrointestinal complaints, including gastric ulcers. In 2001, copalchi bark was listed in the first edition of the Mexican Herbal Pharmacopoeia as a medicinal plant with ethnobotanical uses in Mexico, such as for treating stomach pain, malaria, and diabetes.

The stem-bark infusion is highly valued in contemporary Mexico for the treatment of gastritis and diabetes; the plant is commercialized under the names copalchi, cáscara sagrada, and quina.

2.3 European Introduction and German Research Tradition

The plant's history extends into Europe through trade and medical research. From 1890 to 1913, the stem bark of H. latiflora was subjected to pharmacological investigations at the Instituto Médico Nacional (IMN) in Mexico. These studies included the isolation of a glycoside called "coutareoside" that was later rediscovered by German and French researchers. German pharmaceutical interest in copalchi, particularly as an antidiabetic agent, began in earnest in the mid-20th century and resulted in the commercial product Sucontral, marketed by Harras Pharma Curarina Arzneimittel GmbH in Munich. More than 60 years later, Harras Pharma continues to market the product in Germany; Sucontral is also marketed in the United States and Canada by EuroMedica and EuroPharma (Green Bay, Wisconsin). Studies evaluating therapeutic response in patients with NIDDM (non-insulin-dependent diabetes mellitus) have been reported since 1953.

2.4 Pharmacopeial Recognition

In 2013, a full quality standards monograph for copalchi bark specifications entered the second edition of the Mexican Herbal Pharmacopoeia. The copalchi complex is widely used in Mexico for treating diabetes and gastrointestinal disorders. The first therapeutic use for H. latiflora bark was registered in the Florentine Codex in the sixteenth century. The latest pharmacological and phytochemical studies revealed that the infusion of the leaves has hypoglycemic, antihyperglycemic, and gastroprotective activities. For these reasons, the monograph of the main copalchi species, H. latiflora, was recently added to the Mexican Herbal Pharmacopoeia.

3. Key Chemical Constituents and Active Compounds

3.1 Overview of Primary Constituents

The primary active constituents of copalchi bark include a group dominated by the presence of neoflavonoids (mainly 4-phenylcoumarins) and neoflavonoid glycosides, as well as flavones, flavonols, and phenolcarboxylic acids; and a second group (triterpenes) consisting mainly of cucurbitacins.

Their major components are 4-phenylcoumarins 5,7,3′,4′- or 5,7,4′-substituted with oxygenated functionalities, with the former having the most common pattern. These, along with a few cucurbitacins, are responsible for the antidiabetic properties of both Hintonia species. Within the related species Exostema caribaeum, 4-phenylcoumarins appear to be the primary antimalarial constituents.

3.2 Coutareagenin (Coutareoside Aglycone)

The neoflavonoid coutareagenin — chemically identified as 5-hydroxy-7-methoxy-4-(3,4-dihydroxyphenyl)-2H-benzo-1-pyran-2-one — is consistently identified as the principal biomarker and active constituent of copalchi bark extract. A blood sugar-lowering effect due to oral or intragastric administration of a copalchi native extract (Hintoniae latiflorae cortex) or intragastric administration of the pure substance, coutareagenin (neoflavonoid), was demonstrated with statistically significant results in streptozotocin-induced diabetic rats. This evidence confirms that coutareagenin, one of the active substances contained in Hintonia latiflora bark, produces a reduction of diabetically elevated blood sugar levels; however, the native extract as a whole is regarded as the active substance complex of copalchi bark.

3.3 Cucurbitacins

Extracts from the stem barks of several Mexican copalchi species were tested in three different in vivo models using normal and streptozotocin-induced diabetic rats. From the active extract of H. latiflora, 25-O-acetyl-3-O-β-d-glucopyranosyl-23,24-dihydrocucurbitacin F, an analog of 23,24-dihydrocucurbitacin F, and several known compounds were isolated; this cucurbitacin glycoside was also isolated from H. standleyana. The isolated cucurbitacin glycoside, when administered at doses of 10 mg/kg or 30 mg/kg, significantly reduces blood glucose levels in STZ-induced diabetic rats.

3.4 Other Identified Compounds

Phytochemical work on H. latiflora also yielded the new compound 5-O-[β-d-xylopyranosyl-(1→6)-β-d-glucopyranosyl]-7,4′-dimethoxy-4-phenylcoumarin, along with several known compounds including ursolic acid and desoxycordifolinic acid. Phenylcoumarins in this series showed hypoglycemic activity. Chlorogenic acid has also been identified as a notable bioactive component. The noted antidiabetic action of leaf infusions involves the major active principles chlorogenic acid and a broad diversity of 4-phenylcoumarins. Iridoids, identified as key bioactive compounds in copalchi, are associated with antioxidant and anti-inflammatory benefits, supporting cardioprotective, hypolipidemic, and hepatoprotective effects.

4. Mechanisms of Action

4.1 Alpha-Glucosidase Inhibition

Hintonia is an inhibitor of alpha-glucosidase, an enzyme that releases sugar from foods, particularly carbohydrates. By inhibiting this enzyme at the intestinal brush border, copalchi compounds slow the release of glucose into the bloodstream following carbohydrate ingestion, blunting postprandial glucose spikes. This compound appears to inhibit alpha-glucosidase, an enzyme that releases sugar from carbohydrates, and because Hintonia delays the release of sugar in the bloodstream, it keeps glucose balanced, rather than allowing it to spike as seen in cases of type 2 diabetes.

4.2 Vasodilating Action

It has been shown for the first time that an extract of Hintonia latiflora (HLE) which is used as an antidiabetic herbal medicine is not only able to decrease blood glucose concentration but additionally exerts a vasodilating effect. Accordingly, this extract might have a positive influence on diabetes-associated dysfunction of blood vessels. The vasodilating effect was demonstrated in vitro in aortic rings of guinea pigs as well as in vivo in rabbits.

It can be suggested that the vasodilating effect of HLE is primarily the result of an inhibition of G protein-induced increase in intracellular calcium and not of a blockade of voltage-operated L-type calcium channels. This mechanism is distinct from classical calcium channel blockers. Aortic rings pre-contracted with noradrenaline could completely be relaxed by HLE (EC50: 51.98 mg/l); in contrast, potassium-induced contractions were not diminished by HLE.

4.3 Gastroprotective Mechanism

In preclinical models, the stem-bark and leaf infusions of H. latiflora provoked significant gastroprotective effects, and the mode of action of the active phenylcoumarin compounds involved non-protein sulfhydryl endogenous compounds. Sulfhydryl-mediated gastroprotection is a known mechanism shared with several gastroprotective agents that enhances gastric mucosal defense.

4.4 Overall Phytochemical Synergy

The native extract as a whole is regarded as the active substance (active substance complex) of Hintonia latiflora (Copalchi) bark, suggesting that no single compound fully accounts for all observed biological activities. The interplay between 4-phenylcoumarins, cucurbitacins, and other phenolic compounds appears to drive the overall pharmacological profile.

5. Scientific Evidence by Area of Use

5.1 Glycemic Control in Type 2 Diabetes and Pre-Diabetes

This is the most extensively studied area for copalchi, with multiple open clinical trials conducted primarily in German-speaking Europe. Positive effects of preparations of the bark of the Central American plant Hintonia latiflora (family Rubiaceae) on blood glucose reduction and maintenance of physiologically normal blood glucose values have been reported in scientific investigations published over at least the past 60 years.

Study 1: Long-Term Open Study (up to 33 Months) — Korecova, Hladicova, Korec (2006)

The antidiabetic efficacy and safety of an extract from Hintonia latiflora (drug-extract ratio 1:4.5, extraction solvent 32% ethanol) was tested in a monocenter open, uncontrolled study in 30 patients with type 2 diabetes. Patients were adjusted to a stable diet at least two months prior to therapy and during the entire duration of the study in order to exclude dietary impact. After 12 months of therapy, fasting glucose was reduced by 20.6%, postprandial glucose by 19%, and the mean HbA1c by 10.3% (p < 0.001). In the patients remaining in the study, these parameters were stable thereafter (up to 33 months of treatment). In the patients remaining in the study, these parameters were stable thereafter (up to 33 months of treatment), and there were no hypoglycemic episodes or adverse events throughout the total treatment period.

Study 2: Six-Month Open Prospective Trial — Korecova & Hladikova (2014, European Journal of Medical Research)

A dry concentrated extract from the bark of Hintonia latiflora in capsule form was tested in an open, prospective clinical study in 41 dietetically stabilized subjects with type 2 diabetes. The effects on parameters of blood glucose control were documented over a period of six months. Fasting and postprandial glucose and the HbA1c value declined significantly. In the case of HbA1c, this meant a reduction of the absolute value from 7.49 ± 0.72% to 6.82 ± 0.67% (from 58.4 to 51.0 mmol/mol Hb; intention to treat (ITT) population). Furthermore, cholesterol and triglycerides were slightly reduced, and no negative effect on other laboratory parameters and no change of the liver values were observed. Tolerance was very good. In particular, no side effects and no hypoglycemic episodes or worsening of diabetic symptoms occurred.

Study 3: Eight-Month Multicentric Non-Interventional Study — Schmidt & Hladikova (2014, Naturheilpraxis)

In an open, prospective, multicentric and non-interventional application study, the effects of a dry concentrate from the bark of Hintonia latiflora in capsule form were examined for the laboratory parameters of blood sugar levels (HbA1c, fasting and postprandial glucose) as well as for diabetic accompanying symptoms. Particular attention was given to tolerance and clinical laboratory parameters including blood pressure, liver values, and blood lipids. An eight-month treatment was documented in 178 test persons with type 2 diabetes/pre-diabetes. The HbA1c values improved over the course of the study with a high level of clinical relevance and significance from 7.2 ± 0.4% to 6.4 ± 0.5%. At the end of eight months, researchers noted: HbA1C improved by a significant average of 10.4 percent; fasting glucose improved an average of 23.3 percent; and postprandial glucose decreased by an average of 24.9 percent.

Study 4: Long-Term Open Study with Fluid Extract (10 Months)

Fourteen patients with type 2 diabetes received approximately 10 drops of a copalchi (Hintonia latiflora) extract twice daily for a duration of 10 months. The patients were stabilized to glibenclamide and diet prior to the administration of copalchi drops. In 9 patients, "good" to "very good" improvement of their HbA1c values was found, and in 4 of these patients, glibenclamide could be discontinued within 10 months. With regard to safety, no pathologic changes in liver parameters during long-term application of copalchi drops in 16 subjects with diabetes mellitus were detected.

Evidence Strength Assessment

All published human clinical studies on copalchi are open-label, non-randomized, and uncontrolled. While they consistently show statistically significant improvements in HbA1c, fasting glucose, and postprandial glucose, the absence of placebo arms, blinding, and randomization represents a fundamental limitation. Large-scale, rigorous clinical trials are limited. Reductions in HbA1c across studies are clinically meaningful (approximately 0.5–0.8 percentage points absolute), but cannot be definitively attributed to the botanical in the absence of controlled trials. The evidence should currently be characterized as preliminary positive but methodologically limited.

5.2 Lipid Metabolism

Secondary endpoints in several glycemic control trials reported lipid changes. In the 2014 six-month trial, cholesterol and triglycerides were slightly reduced. Similar observations were noted in the 8-month multicentric study. These findings are consistent but represent secondary, uncontrolled observations within studies not designed to assess lipid outcomes as primary endpoints. Evidence for lipid-lowering effects is therefore weak and preliminary.

5.3 Gastrointestinal Protection

A study was undertaken to establish the acute toxicity and preclinical efficacy for treating gastrointestinal disorders of the infusions of two Mexican copalchis. The findings of the investigation provided scientific support for the centennial popular use of the stem-barks of both Hintonia species for treating gastric complaints. In preclinical (rodent) models, the stem-bark and leaf extracts of both species provoked significant gastroprotective effects: H. latiflora stem-bark (HLSB) demonstrated 80.5 ± 3.35% gastroprotection (ED50 = 184.7 mg/kg). The gastroprotective effect of the leaf aqueous extracts provides an alternative for the popularly used crude drug, being a valuable discovery in terms of natural resource conservation.

All gastroprotective evidence remains at the preclinical (animal) level. No human clinical trials have investigated copalchi for gastrointestinal outcomes.

5.4 Antimalarial Activity

Although a concentration of 1,200 mg/kg of H. latiflora methanolic extract (HlMeOHe) slowed down parasite replication, retarded the patency time, and increased the survival time of P. yoelii yoelii-infected mice, its chemical composition should be studied in detail in order to reduce its genotoxic potential. Within the copalchi complex, Exostema caribaeum contains mostly 4-phenylcoumarins, which are the apparent antimalarial constituents of these plants.

Antimalarial evidence for copalchi/H. latiflora remains preclinical only, with significant safety concerns at effective doses.

5.5 Vasodilation and Cardiovascular Parameters

As detailed in Section 4.2, the vasodilating effect of H. latiflora extract has been demonstrated in preclinical models. An extract of Hintonia latiflora (HLE), used as an antidiabetic herbal medicine, is not only able to decrease blood glucose concentration but additionally exerts a vasodilating effect, and accordingly this extract might have a positive influence on diabetes-associated dysfunction of blood vessels. Blood pressure improvements were noted as secondary outcomes in some clinical observational studies, but no dedicated human cardiovascular trials have been published.

5.6 Antioxidant and Anti-inflammatory Activity

Iridoids, identified as key bioactive compounds in copalchi, offer significant antioxidant and anti-inflammatory benefits, supporting cardioprotective, hypolipidemic, and hepatoprotective effects. These activities have been characterized principally in in vitro or preclinical models and have not been evaluated in dedicated human trials.

5.7 Antinociceptive Activity

Research at UNAM has identified antinociceptive properties in H. standleyana. Antinociceptive activity of 3-O-β-d-glucopyranosyl-23,24-dihydrocucurbitacin F from Hintonia standleyana (Rubiaceae) has been pharmacologically characterized. This evidence is preclinical and pertains primarily to a related species rather than H. latiflora itself.

6. Body Systems and Health Areas Associated with Copalchi

• Endocrine / Metabolic System: Copalchi is traditionally associated with type 2 diabetes (mild to moderate), hyperglycemia, dyslipidemia (high cholesterol), and hypertriglyceridemia (high triglycerides).
• Gastrointestinal System: Used in folk medicine for gastrointestinal complaints including gastric ulcers, with preclinical evidence of gastroprotective effects.
• Cardiovascular System: Preclinical evidence indicates vasodilating properties that might have a positive influence on diabetes-associated vascular dysfunction.
• Infectious Disease (Traditional): Documented therapeutic properties include antidiabetic, gastroprotective, antimalarial, and antimicrobial activity, mostly of the stem-bark of H. latiflora.

7. Dosage Forms and Reported Dosages

The following dosages are reported specifically as used in identified studies and should not be interpreted outside the context of those investigations:

• Capsules (dry concentrate, DER 2.4:1, 32% ethanol): 100 mg of dry concentrate per capsule, used in the 2014 six-month trial by Korecova & Hladikova.
• Liquid extract (DER 1:4.5, 32% ethanol): Used in the long-term 33-month study; approximately 10 drops of a copalchi extract twice daily for 10 months in one long-term open study.
• Liquid drops (historical clinical validation): Dosages applied to patients with mild to moderate diabetes ranged between 3 × 30–50 drops per day.
• Traditional infusion: The bark was traditionally brewed into teas or decoctions. In case of infusions, it is important not to exceed the boiling time of the bark, as prolonged boiling may reduce the content of some active compounds.
• Pharmacopeial standard: The copalchi monograph in the Mexican Herbal Pharmacopoeia requires the dried bark to contain a minimum specified level of the principal 4-phenylcoumarin compounds.

8. Safety Considerations and Known Interactions

8.1 Hepatotoxicity — Key Safety Signal

Hepatotoxicity is the most significant safety concern identified in the scientific literature for copalchi. Cases of acute hepatotoxicity have been reported with an increase in hepatic transaminases (ALT and AST) by the continuous consumption of this bark. A notable Spanish case series (Bruguera et al., 2007, Gastroenterología y Hepatología) documented acute hepatitis associated with copalchi consumption; this represents clinical case-level evidence of liver injury in humans.

Preclinical evidence further substantiates hepatic risk at higher doses. A study evaluated the histopathological effect of 200 and 1,000 mg/kg of H. latiflora methanolic stem bark extract (HlMeOHe) in the small bowel, liver, pancreas, kidneys, and brain of CD-1 male mice after oral sub-acute treatment for 28 days. No histopathological alterations were observed in the brain and small bowel; however, mice presented diarrhea from day 2 of treatment with both doses. Animals treated with the higher dose showed, in liver sections, hydropic degeneration, hepatitis, and necrosis; kidney sections depicted tubular necrosis; and in pancreas sections, hydropic degeneration of the pancreatic islets was observed. In conclusion, HlMeOHe damaged the liver with an oral dose of 200 mg/kg, and at 1,000 mg/kg injured the kidneys and pancreas of the CD-1 male mice.

The extract type used in toxicology studies (methanolic) differs from that used in clinical trials (aqueous/ethanolic at lower ratios), which is an important caveat. Water is mostly used in natural medicine practice for extraction; however, this solvent does not extract a wide range of active molecules contained in the plant. This distinction between extraction methods may explain apparent discrepancies in observed toxicity profiles across studies.

8.2 Acute Toxicity of Aqueous Preparations

In a contrasting finding with aqueous/infusion preparations, investigation of the acute toxicity revealed that infusions of the leaves (HLL and HSL) and stem barks (HLSB and HSSB) of both Hintonia species were not toxic to mice (LD50 > 5,000 mg/kg in all cases). This finding suggests that the solvent of extraction is a critical determinant of the safety profile.

8.3 Genotoxicity Concern

The antimalarial study using methanolic extract raised genotoxic concerns at effective antimalarial doses. Although a concentration of 1,200 mg/kg of HlMeOHe slowed parasite replication and increased survival time of infected mice, its chemical composition should be studied in detail in order to reduce its genotoxic potential.

8.4 Gastrointestinal Adverse Effects

Copalchi bark is intensely bitter, which can cause gastrointestinal irritation in sensitive individuals. Symptoms such as nausea, bloating, mild abdominal pain, or belching can occur when consuming too much of the infusion or extract. In preclinical sub-acute studies, mice presented diarrhea from day 2 of treatment with both dose levels tested.

8.5 Hypoglycemia Risk in Combination with Antidiabetic Drugs

Given its demonstrated blood glucose-lowering activity, additive hypoglycemic effects are plausible when copalchi is combined with conventional antidiabetic medications. In the long-term clinical studies reviewed, there were no hypoglycemic episodes or adverse events throughout the total treatment period in participants on dietary management. However, the study design did not systematically investigate combination use with pharmaceutical hypoglycemic agents. Regular monitoring of blood glucose levels is advisable, especially when combining copalchi with hypoglycemic medications.

8.6 Limitations of the Safety Dataset

Hintonia latiflora is a tree native to the American continent belonging to the Rubiaceae family, and its stem bark is empirically used mainly to treat diabetes and malaria; supplements containing H. latiflora are sold in America and Europe without medical prescription, thus scientific information regarding its toxicity as a consequence of regular consumption is needed. The favourable liver safety findings from the controlled clinical trials (dry ethanolic extract, 100 mg DER 2.4:1) showed no negative effect on liver values, but longer-term, larger-scale and controlled safety studies have not been published. The human hepatotoxicity case series and the animal histopathological data together indicate that extract form, dose, duration, and individual susceptibility are critical variables.

8.7 Variability and Adulteration

Because the copalchi complex includes multiple species from two different plant families, product quality and species identity are recognized challenges. The complementary use of molecular and chemical markers will assure the quality of plant material used in traditional medicine for therapeutic purposes, and this is considered valuable new information for National Health authorities as a part of the Mexican Herbal Pharmacopoeia. Misidentification of the source species is a documented concern in the commercialized market.

References

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