Antimycobacterial activity of medicinal plants used by the Mayo people of Sonora, Mexico.
BACKGROUND
Tuberculosis (TB) is an infectious disease mainly caused by Mycobacterium tuberculosis (Mtb), which generates 9 million new cases worldwide each year. The Mayo ethnicity of southern Sonora, Mexico is more than 2000 years old, and the Mayos possess extensive knowledge of traditional medicine.


OBJECTIVE
To evaluate the antimycobacterial activity levels of extracts of medicinal plants used by the Mayos against Mtb and Mycobacterium smegmatis (Msm) in the treatment of TB, respiratory diseases and related symptoms.


METHODS
A total of 34 plant species were collected, and 191 extracts were created with n-hexane, dichloromethane, ethyl acetate (EtOAc), methanol and water. Their minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined against Mtb H37Rv using the microplate alamar blue assay (MABA) and against Msm using the resazurin microplate assay (REMA) at 6 and 2 days of exposure, respectively, and at concentrations of 250-1.9µg/mL (n-hexane extracts) and 1000-7.81µg/mL (extracts obtained with dichloromethane, EtOAc, methanol and water).


RESULTS
Rhynchosia precatoria (Willd.) DC. (n-hexane root extract), Euphorbia albomarginata Torr. and A. Gray. (EtOAc shoot extract) and Helianthus annuus L. (n-hexane stem extract) were the most active plants against Mtb H37Rv, with MICs of 15.6, 250, 250µg/mL and MBCs of 31.25, 250, 250µg/mL, respectively. R. precatoria (root) was the only active plant against Msm, with MIC and MBC values of ≥250µg/mL. None of the aqueous extracts were active.


CONCLUSIONS
This study validates the medicinal use of certain plants used by the Mayo people in the treatment of TB and related symptoms. R. precatoria, E. albomarginata and H. annuus are promising plant sources of active compounds that act against Mtb H37Rv. To our knowledge, this is the first time that their antimycobacterial activity has been reported. Crude extracts obtained with n-hexane, EtOAc and dichloromethane were the most active against Mtb H37Rv.
Departamento de Biotecnología y Ciencias Alimentarias, Instituto Tecnológico de Sonora, 5 de Febrero 818 Sur, 85000 Ciudad Obregón, Sonora, Mexico.
Enrique Wenceslao
EW
Coronado-Aceves
Herbario USON, Departamento de Investigaciones Científicas y Tecnológicas, Universidad de Sonora, Niños Héroes entre Rosales y José María Pino Suárez, Edificio 1A (Museo), Colonia Centro, 83000 Hermosillo, Sonora, Mexico.
José Jesús
JJ
Sánchez-Escalante
Departamento de Biotecnología y Ciencias Alimentarias, Instituto Tecnológico de Sonora, 5 de Febrero 818 Sur, 85000 Ciudad Obregón, Sonora, Mexico.
Jaime
J
López-Cervantes
Departamento de Ciencias Químico Biológicas, Universidad de Sonora, Encinas y Rosales, Colonia Centro, 83000 Hermosillo, Sonora, Mexico.
Ramón Enrique
RE
Robles-Zepeda
Departamento de Ciencias Químico Biológicas, Universidad de Sonora, Encinas y Rosales, Colonia Centro, 83000 Hermosillo, Sonora, Mexico.
Carlos
C
Velázquez
Departamento de Biotecnología y Ciencias Alimentarias, Instituto Tecnológico de Sonora, 5 de Febrero 818 Sur, 85000 Ciudad Obregón, Sonora, Mexico.
Dalia Isabel
DI
Sánchez-Machado
Departamento de Ciencias Químico Biológicas, Universidad de Sonora, Encinas y Rosales, Colonia Centro, 83000 Hermosillo, Sonora, Mexico. Electronic address: agaribay@guayacan.uson.mx.
Adriana
A
Garibay-Escobar
D000085:Acetates / Q000737:chemistry; D000995:Antitubercular Agents / Q000302:isolation & purification / Q000494:pharmacology*; D019448:Ethnobotany; D020834:Ethnopharmacology; D028481:Euphorbia / Q000737:chemistry*; D007887:Fabaceae / Q000737:chemistry*; D006368:Helianthus / Q000737:chemistry*; D006586:Hexanes / Q000737:chemistry; D006801:Humans; D008519:Medicine, Traditional; D008752:Methylene Chloride / Q000737:chemistry; D008800:Mexico; D008826:Microbial Sensitivity Tests; D020102:Mycobacterium smegmatis / Q000187:drug effects* / Q000254:growth & development; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000254:growth & development; D008517:Phytotherapy; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D010946:Plants, Medicinal; D012997:Solvents / Q000737:chemistry; D014376:Tuberculosis / Q000188:drug therapy* / Q000382:microbiology
D000085:Acetates; D000995:Antitubercular Agents; D006586:Hexanes; D010936:Plant Extracts; D012997:Solvents; C026385:n-hexane; D008752:Methylene Chloride; C007650:ethyl acetate
MABA; Mayo; Mycobacterium; REMA; Rhynchosia; Tuberculosis