Abstract
The copalchi complex, Hintonia latiflora, H. standleyana, and Exostema caribaeum, 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 have 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. Nevertheless, quality control parameters are focused to the bark but not to the leaves. Moreover, information about other Rubiaceae species is needed. The main goal of this study was to generate molecular and chemical markers for quality control of the copalchi complex raw material. In addition, the resolution of the taxonomical ambiguity between H. latiflora and H. standleyana, as well as the testing of the molecular and chemical markers in different geographical batches, were aims of this study. The molecular markers and chemical profiles of the leaf infusions were generated considering three different populations for H. latiflora and separate individuals of the three species (HL, n = 10; HS, n = 3; EC, n = 4). The molecular markers matK, rbcL, trnH-psbA, rpl32-trnL, and ITS2 were tested for their discriminating capabilities. Chemical profiles of the leaf infusions were obtained by means of HPLC analyses using chlorogenic acid and 4-phenylcoumarins as chemical markers. The concatenated sequence of the molecular markers trnH-psbA, rpl32-trnL, and ITS2 clearly distinguished the three taxa, clarifying the taxonomical ambiguity of the Hintonia genus. Additionally, the chemical profiles allowed the unequivocal identification of each species supporting the molecular results; the geographical origin of the samples did not modify neither the chemical profiles nor the concatenated sequence of H. latiflora, suggesting that it is a robust identity test. The complementary use of molecular and chemical markers will assure the quality of plant material used in traditional medicine for therapeutic purposes, and should be valuable new information for the National Health authorities as a part of the Mexican Herbal Pharmacopoeia.
Highlights
Hintonia latiflora (Sessé et Mociño ex DC.) Bullock, Hintonia standleyana Bullock and Exostema caribaeum (Jacq.) Roem. et Schult. are the main, and highly commercialized, species that conform the Rubiaceae section of a medicinal plant complex known as the copalchi complex (Linares and Bye, 1987)
There is a taxonomical disagreement about the identity of H. standleyana; some authors recognizes the existence of H. standleyana as a taxon (Borhidi and Diego-Pérez, 2002; Stranczinger et al, 2006); where as other specialists state that this species is a synonym of H. latiflora (Ochoterena-Booth, 2000; Motley et al, 2005; Martínez-Cabrera et al, 2014); morphological and molecular data were analized in both cases but chemical analysis was never used for clarify this taxonomical ambiguity
Among the 17 plant specimens used in this study, the protocols for DNA extraction, PCR and DNA sequencing functioned for 13 (76.47%), 12 (70.58%), and 11 (64.71%) of individuals analyzed using molecular markers trnH-psbA, ITS2, and rpl32trnL, respectively
Summary
Hintonia latiflora (Sessé et Mociño ex DC.) Bullock, Hintonia standleyana Bullock and Exostema caribaeum (Jacq.) Roem. et Schult. are the main, and highly commercialized, species that conform the Rubiaceae section of a medicinal plant complex known as the copalchi complex (Linares and Bye, 1987). Hintonia latiflora (Sessé et Mociño ex DC.) Bullock, Hintonia standleyana Bullock and Exostema caribaeum (Jacq.) Roem. The definition of the copalchi complex is intricate because of the addition of other poorly studied Rubiaceae species such as Coutarea hexandra (Jacq.) K. In contemporary Mexico, the copalchi complex, H. latiflora, H. standleyana, and E. caribaeum, is in widespread use for treating diabetes (Mata et al, 2013), generating a great pressure over its wild populations, because all the crude drug supply is derived from wild individuals. A recent risk study of the wild medicinal species traded in the Balsas Basin, shows that H. latiflora is ranked in the third place of endangered species, whereas E. caribaeum is located in the top 50 (Beltrán-Rodríguez et al, 2017). The harvesters, motivated for the price market, increased decortication which in turn has endangered the wild populations (Martínez-Pérez et al, 2012; Reyes-García et al, 2012; Monroy-Ortiz et al, 2013)
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