Two decades of Mexican ethnobotany and research in plant drugs

A renewed interest in the systematic study of indigenous medicines and associated medicinal plants arose in the 1970s. In Mexico the government established a national pharmaceutical industry to make use of the valuable colonial heritage of traditional practices combined with European medical concepts and resources. In 1975 the Mexican Institute for the Study of Medical Plants was created to integrate botanical, chemical and pharmacological studies on the Mexican flora. It compiled a database on ethnobotanical information relating to Mexican medicinal plants from the medical literature of the 16th to 19th centuries. A second database contained information on medicinal plants in current use. A medicinal herbarium was established. Taxonomical studies led to classification of the 11,000 voucher specimens in the herbarium and cross-referencing of the information with other databanks. A core group of 1000 plants used in traditional medicine throughout Mexico for almost 400 years was identified. Most of these are used to treat common diseases or basic health problems, usually given orally as decoctions or infusions. 95% of the plants used traditionally are from wild species. Information was collected from almost 3000 small Indian communities over four years on three aspects of traditional medicine--the healer, the disease categories recognized and the therapeutic resources in use. Plants with reported medicinal activity were selected for laboratory screening according to the frequency and commonality of their use, geographical distribution and seasonal availability. Screening involves a collaboration between chemists and pharmacologists: plant extracts are sequentially assayed and fractionated until the pure compound is isolated. Several active compounds are usually obtained from the same extract, frequently from the aqueous fractions. Ethnomedical information influences which plants are selected for screening and the type of assay used.

Pharmacognostical studies of the plant drug Mimosae tenuiflorae cortex

The bark of the Mimosa tenuiflora (Willd.) Poiret (Leguminoseae) tree, known as tepescohuite in Mexico, is commonly used in this country and in Central America to elaborate different products for the treatment of skin burns and lesions. The cicatrizing properties of extracts obtained from this bark have been scientifically studied, attributing the main biological activity to its tannin and saponin content. Studies include clinical trials of phytodrugs based on Mimosae tenuiflora bark extracts for treatment of venous leg ulcerations. Recent commercialization of the plant drug Mimosae tenuiflorae cortex requires pharmacognostical information to develop quality-control methods for raw materials and extracts produced with this plant drug. The present paper reports a group of ethnobotanical, morphological, chemical, and molecular studies performed with Mimosae tenuiflora materials obtained by collection in the southeastern Mexican state of Chiapas. Macro- and micro-morphological parameters were established to authenticate the genuine drug that allowed detection of adulterants usually found in commercial samples of this plant material. These morphological characteristics can be used for rapid identification of the drug and are particularly useful in the case of powdered materials. The chemical studies performed demonstrated that tannins represent the major component group in the bark. Its content in genuine tepescohuite is 16% and is mainly composed of proanthocyanidins, a condition permitting a tannin-based chemical-control method for fingerprinting the plant drug. Contrariwise, the saponin concentration in Mimosae tenuiflora bark is extremely low, and its isolation and content evaluation represent a complex procedure that is unsuitable for routine control purposes. Finally, random amplified DNA (RAPD) analysis results a useful tool for obtaining DNA specific markers of Mimosae tenuiflora species which should be useful in future studies involving raw material authentication by molecular methods.

Immunomodulatory activity of Chilean Cyttaria species in mice with L5178Y lymphoma

The immunomodulatory effect of hydrosoluble extracts of four Chilean Cyttaria species (Discomycetes, Fungi) was assessed in mice with L5178Y lymphoma. Oral administration of 100 mg extract per day for 7 days enhanced the percentual phagocytosis and phagocytosis index in animals receiving Cyttaria berteroi, Cyttaria darwinii, Cyttaria espinosae and Cyttaria harioti extracts. Differences in the digestion index were observed in mice treated with C. darwinii and C. berteroi. In the delayed-type hypersensitivity model, only C. harioti was able to modify the immune response. The results suggest that intake of Cyttaria can improve the immune system of consumers.

An experimental model of stress-induced immunosuppression produced by electrical stimulation of the brain in the rat

The present paper reports a model of stress induction, based on electrical stimulation of the brain in normal Wistar rats. Stress-related stimulation of the hypothalamic-pituitary-adrenal axis produced a rise in circulating corticosterone levels that correlated significantly with the impairment of some immunological parameters, such as delayed hypersensitivity reactions to dinitrofluorobenzene and to sheep red blood cells, together with changes in splenocyte proliferation and phagocytic activity of peritoneal macrophages. This experimentally elicited stress in the rat is proposed as a suitable model of immunosuppression that could be used for the evaluation of drugs with potential immunomodulatory properties.

Phenytoin and electric shock-induced apoptosis in rat peripheral blood lymphocytes

The apoptotic index (AI) of peripheral blood lymphocytes (PBL) and plasma corticosterone (CS) levels were determined in Wistar rats treated with phenytoin (PHT) at therapeutic and toxic doses (100 or 200 mg/kg/day, respectively, over a period of 7 days) and stressed by bifrontal electric shock (60 Hz/40 mA/0.2 seg). The values of CS and AI were found to be significantly higher in rats submitted to electric shock (ES) and in rats treated with therapeutic and toxic doses of PHT plus ES, than in rats treated only with PHT (P<0.001). The plasma concentrations of PHT were found to be significantly higher in rats treated with toxic doses than in those treated with therapeutic doses (P<0.001), while the control group (without treatment) and vehicle group (propilenglycol-ethanol-water, 40:10:50), showed low levels of CS, and less than 1% of AI. The DNA analysis by electrophoresis in agarose in all the groups was positive, displaying the ladder pattern characteristic of apoptotic process (200 bp), except in the control groups (no treatment and vehicle treated). Our results demonstrate that chronic stress, caused by ES, produces an elevation of CS. The values of apoptosis were correlated with the CS levels, suggesting that the apoptotic inductor process is a consequence of an increase in the concentration of corticosterone in plasma, in response to the hypothalamic-pituitary-adrenals (HPA) axis activation, while phenytoin at therapeutic doses is only a moderate apoptosis inductor.

Antimicrobial compounds detected in Bocconia arborea extracts by a direct bioautographic method

BACKGROUND

Among the numerous in vitro methods for studying the antimicrobial activity of plant drugs, bioautography has found widespread applications, especially for the detection of new compounds in complex plant extracts.

METHODS

This paper describes the results obtained during the application of the bioautographic method to detect antimicrobial compounds in a chloroformic extract of leaves and stems of Bocconia arborea, a plant used profusely in traditional medicine for the treatment of diverse infectious diseases.

RESULTS AND CONCLUSIONS

The methods allows for the detection of spots of growth inhibition of cultures directly in the extract thin layer chromatographic plate previously dispersed with a broth culture containing the microorganisms. The procedure also allowed for the detection of the presence of several products in the B. arborea extract with considerable activity against five different microorganisms. Additionally, the method allowed the determination that the antimicrobial activity is due to compounds of probable alkaloid origin.

Antimicrobial evaluation of some plants used in Mexican traditional medicine for the treatment of infectious diseases

Twelve methanolic plant extracts from botanical species used in traditional medicine in Morelos, México to cure infectious diseases have been subjected to a screening study to detect potential antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. The antimicrobial activity of the products was evaluated using colonies growing in solid medium, establishing the minimal concentration required to inhibit their in vitro growth (MIC). The results showed that extracts from Eucalyptus globolus Labill, Punica granatum L., Artemisia mexicana Wild., and Bocconia arborea Watt. possess strong in vitro antimicrobial activity against the tested microorganisms.

Calcium-antagonist effects of quercetin on aortic smooth muscle

Relaxation induced by quercetin was studied on aortic rings depolarized with KCl and on Ca2+ dependent aortic contraction. Quercetin's actions as a cyclooxygenase inhibitor were compared with those of indomethacin. To determine the possible effects of quercetin on internal Ca2+ mobilization, it was assayed on aortic muscle contracted with caffeine. Quercetin relaxes aortic smooth muscle contracted with KCl (RC50 = 1.8 x 10(-4) M) and induces a rightward displacement of Ca2+ curves. The relaxation induced by quercetin is higher than that produced by indomethacin, suggesting that its action is independent of cyclooxygenase inhibition. Caffeine-induced aortic contraction was not modified by quercetin, suggesting that its effect should not involve internal calcium modulation. Our results further support the thesis that the spasmolytic action of quercetin arises from its negative modulation of calcium entry to the smooth muscle.

[Effect produced by the alkaloid fraction of Mimosa tenuiflora (tepescohuite) on the peristaltic reflex of the guinea pig ileum]

An alkaloidal fraction was obtained from Mimosa tenuiflora (Willd.) Poir (tepescohuite) trunk bark. The product contained mainly an indolealkylamine and three minor alkaloids. This fraction inhibited the peristaltic reflex in the guinea-pig isolated ileum in vitro.

[Model of intraluminal perfusion of the guinea pig ileum in vitro in the study of the antidiarrheal properties of the guava (Psidium guajava)]

An experimental in vitro model was developed for the study of plant extracts reported by traditional medicines in the treatment of diarrhea. The guinea-pig isolated ileum is perfused with the plant extract using an intraluminal approach. The peristaltic reflex is induced by electrical stimulation while the plant extract is perfused. The spasmolytic effects of Psidium guajava leaf methanol, hexane and water extracts were demonstrated suggesting the existence of two different types of active components. The results obtained allow to propose this in vitro method as a useful model to reproduce some of the characteristics of the oral way of administration of plant extracts.

[Pharmacological properties in vitro of various extracts of Mimosa tenuiflora (tepescohuite)]

The in vitro biological effects of polar extracts of Mimosa tenuiflora (Willd.) Poir. trunk bark (tepescohuite) were studied. Ethyl acetate extract, with a high tannin content, inhibited the growth of different microorganisms. Alkaloids were particularly abundant in the butanol extract and this product strongly inhibited the intestinal peristalsis and produced contraction of uterine and gastric strips of rat and guinea pig. Saponins were detected in butanol and methanol extracts producing hemolysis. The screenings performed showed the diversity of bioactive compounds present in this plant product.

[Effect of a dehydrated extract of nopal (Opuntia ficus indica Mill.) on blood glucose]

To assess if a dehydrated extract of nopal stems retains the effect on glycemia of the entire nopal stems two experiments were performed. A. Six patients with type II diabetes mellitus in fasting condition received 30 capsules containing 10.1 +/- 0.3 g of the extract, and serum glucose levels were measured hourly from 0 to 180 minutes. B. Six healthy volunteers received 30 capsules with the extract followed by 74 g of dextrose orally. Serum glucose measurements were made in a similar fashion. In each experiment a control test with empty capsules was performed. Nopal extract did not reduce fasting glycemia in diabetic subjects. Nevertheless, the extract diminished the increase of serum glucose which followed a dextrose load. Peak serum glucose was 20.3 +/- 18.2 mg/dl (X +/- SD) lower in the test with nopal than in the control one (P less than 0.025). Dehydrated extract of nopal (Opuntia ficus-indica Mill) did not show acute hypoglycemic effect, although could attenuate postprandial hyperglycemia.

Experimental evaluation of mimosa tenuiflora (willd.) poir. (Tepescohuite) I. Screening of the antimicrobial properties of bark extracts

Mimosa tenuiflora (Willd.) Poir, is a tree from the south areas of Mexico. This bark is popularly used as remedy to treat different skin lesions. The present study demonstrates the in vitro antimicrobial properties of the water and ethanolic extracts prepared with the dried and powdered bark of this plant. A clear inhibition growth effect was observed in all the gram positive and gram negative organisms, yeasts and dermatophytes used.

The in vitro effect of grandiflorenic acid and zoapatle aqueous crude extract upon spontaneous contractility of the rat uterus during oestrus cycle

Montanoa tomentosa (zoapatle) is a Mexican plant popularly used for antifertility purposes and with promising characteristics for the development of a new oral contraceptive agent with uteroevacuant properties. In a previous pharmacological report we established the ambivalent myometrial response to zoapatle leaves aqueous extract (ZACE) depending on the animal species used and on the existence or absence of pregnancy. This fact could be useful in determining an appropriate medical use of zoapatle and suggests an interesting possible hormonal dependence in its mechanism of action. To elucidate the ZACE effect upon the pattern of uterine contractility in different hormonal stages, the rat uterus in vitro during oestrus cycle was studied. The aqueous crude extract of Montanoa tomentosa leaves produced different (or even opposite), effects on uterine motility during the distinct phases of the oestrus cycle in the rat. Furthermore, pure grandiflorenic acid (GA), obtained from the phytochemical work up of this plant reproduced the uterine responses induced by ZACE. The action of zoapatle is discussed in relation to hormonal stage and to a probable adrenergic mechanism involved.

The zoapatle II--botanical and ecological determinants

A collection of Montanoa (Cerv) specimens was conducted throughout Mexico. Twenty-one specimens were classified, some of them grown in the greenhouse and transplanted in an agricultural experimental field station in the Valley of Mexico. In vitro uterotonic potency was assayed and the results expressed as equivalents of oxytocine, by using estrogenized guinea pig uterine strips. A great variation of uterotonic potency was observed among the wild plants. A clear decrease and uniformity of uterotonic potency was found in plants grown in the experimental field. The study points out the importance of ecological variations in expression of the plant's biological activity.

The zoapatle IV--toxicological and clinical studies

The zoapatle aqueous crude extract has been used in Mexico for the last 5 centuries for the induction of labor, treatment of post-partum bleeding problems, and as a menses inducer. Today, it is sold in street markets, and its long documented history of use by humans could be taken as indirect evidence of a lack of toxicity. Rigorous pharmacological and clinical studies described here, fully confirm the empirical observations.

The zoapatle V--the effect of kauradienoic acid upon uterine contractility

Kauradienoic acid was obtained from the hexanic extract of M. tomentosa (Cerv) leaves by chromatographic separation. This substance influenced the in vitro contractility of the rat, dog and guinea pig uterine strips. It also induced strong contractions of the guinea pig uterus in vivo when administered intravenously, without changes on arterial blood pressure. The effects produced by the plant infusion, the hexanic extract and pure species were compared. The hexanic of other utero-active compounds in M. tomentosa in addition to those already described is discussed.

The zoapatle III--biological and uterotonic properties of aqueous plant extract

Differences in uterotonic activity were observed between zoapatle Montanoa (Cerv.), plants growing in their natural habitat and plants growing in an experimental agricultural plot. Details of an in vitro analogic model for assaying uterotonic potency in guinea pig strips is described. Important species differences on the uterine response to zoapatle aqueous crude extract were noticed in rats, hamsters, guinea pigs, cats and Rhesus monkeys. The need for proper biological evaluation of chemical substances already isolated from zoapatle specimens, is mentioned, and the advantages of working with zoapatle specimens grown under controlled ecological conditions are pointed out.

Active components in Perezia roots

The effects produced by perezone, which was isolated from Perezia cuernavacana Rob. et Greenm., and hydroxyperezone monoangelate, from Perezia hebeclada (D.C.) A.Gray, on intestinal motility in vivo and in vitro in animal experiments are reported. It is suggested that hydroxyperezone monoangelate is a laxative principle present in certain species of the Perezia genus, with use in Mexican folk medicine.

A uterotonic substance from Annona cherimola seeds

Water extract from seeds of Annona cherimola was tested in vitro on uterus strips of nongravid guinea-pigs. The extract resulted in possessing utero-constrictive properties due to the presence of a gluco-steroidal substance isolated from it.

Mexican medicinal plants used for treatment of cardiovascular diseases

This article reviews the state of research for a number of plants traditionally related to treatment of cardiovascular diseases. It stresses the importance of both anthropological surveys and historical studies for the proper understanding of this ancient and still very popular medicine.