title: Antidiabetic potential of two medicinal plants used in Gabonese folk medicine.
abstract: BACKGROUND
  Diabetes mellitus is a metabolic disorder which is rising globally in rich and developing countries. In the African region this rate is the highest, with 20 million diagnosed diabetics. Despite a noticeable progress in the treatment of diabetes mellitus by synthetic drugs, the search for new natural anti-diabetic agents is going on. Nauclea diderrichii (De Wild.) Merr. (ND) and Sarcocephalus pobeguinii Hua ex Pellegr. (SP) are used as traditional medicines in Gabon for the treatment of different diseases, especially in the case of diabetes. The aim of this study was to evaluate the antidiabetic potential of these two medicinal plants traditionally used in Gabon.
  
  
  METHODS
  Pharmacological (inhibitory action on α and β-glucosidases) and toxicological (effect on human T cell proliferation) studies were conducted on aqueous extracts of ND (leaves and bark) and SP (bark) collected in Gabon. All raw extracts were analyzed by HPTLC and their content in phenolic compounds was determined by using standard method. The most active extracts were submitted to preparative HPLC in order to evidence the most efficient subfractions by biological evaluation.
  
  
  RESULTS
  The results showed that two extracts from ND were potent α-glucosidase inhibitors, the leaf extract being more active that the bark extract: the first one was more than 60 fold more active than Acarbose, which is an oral medication used to treat type 2 diabetes; the extract from SP bark was less efficient. The HPLC subfractions of the extracts of ND leaves and SP bark were tested in the same experimental conditions. In each case, the most active subfractions still show very potent inhibitory effect on α-glucosidase (80-90% inhibition at 0.1 mg/mL). The most efficient extract, from ND leaves, was also characterized by the highest percentage of phenolic compounds, which suggests a relationship between its inhibitory potential on α-glucosidase and its content in phenolic compounds. Conversely, only a moderate inhibitory activity of the three extracts was observed on β-glucosidase.
  
  
  CONCLUSIONS
  These results clearly indicated that active compounds present in N. diderrichii and S. pobeguinii leaves or/and bark were selective and highly potent inhibitors of α-glucosidase and validate their popular use for the treatment of diabetes.
authors.affiliation: Laboratoire de Substances Naturelles et de Synthèses Organométalliques (LASNSOM), Université des Sciences et Techniques de Masuku, Faculté des Sciences B.P. 943, Franceville, Gabon. ahuguette2001@yahoo.fr.
authors.forename: Huguette
authors.initials: H
authors.lastname: Agnaniet
authors.affiliation: Laboratoire de Substances Naturelles et de Synthèses Organométalliques (LASNSOM), Université des Sciences et Techniques de Masuku, Faculté des Sciences B.P. 943, Franceville, Gabon.
authors.forename: Elvis Jolinom
authors.initials: EJ
authors.lastname: Mbot
authors.affiliation: Institut des Sciences Appliquées (ISA)-Département de Génie Biologique (GB)-Biochimie-Université des Sciences, des Techniques et des Technologies de Bamako (USTTB) BPE, 423 Bamako - Hamdallaye ACI 2000 - Rue : 405, Porte, 359, Mali.
authors.forename: Ousmane
authors.initials: O
authors.lastname: Keita
authors.affiliation: Institut des Biomolécules Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier-ENSCM, Bâtiment E, Faculté de Pharmacie, 15, avenue Charles Flahault BP14491, 34093, Montpellier, cedex 5, France.
authors.forename: Jean-Alain
authors.initials: JA
authors.lastname: Fehrentz
authors.affiliation: CAMAG Laboratory, Sonnenmattstrasse 11, 4132, Muttenz, Switzerland.
authors.forename: Anita
authors.initials: A
authors.lastname: Ankli
authors.affiliation: Institut des Biomolécules Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier-ENSCM, Bâtiment E, Faculté de Pharmacie, 15, avenue Charles Flahault BP14491, 34093, Montpellier, cedex 5, France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Gallud
authors.affiliation: Institut des Biomolécules Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier-ENSCM, Bâtiment E, Faculté de Pharmacie, 15, avenue Charles Flahault BP14491, 34093, Montpellier, cedex 5, France.
authors.forename: Marcel
authors.initials: M
authors.lastname: Garcia
authors.affiliation: Institut des Biomolécules Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier-ENSCM, Bâtiment E, Faculté de Pharmacie, 15, avenue Charles Flahault BP14491, 34093, Montpellier, cedex 5, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Gary-Bobo
authors.affiliation: Laboratoire de Substances Naturelles et de Synthèses Organométalliques (LASNSOM), Université des Sciences et Techniques de Masuku, Faculté des Sciences B.P. 943, Franceville, Gabon.
authors.forename: Jacques
authors.initials: J
authors.lastname: Lebibi
authors.affiliation: CIBLOT, IPSIT - IFR141, 5 rue Jean Baptiste Clément, 92290, Chatenay-Malabry, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Cresteil
authors.affiliation: Institut des Biomolécules Max Mousseron (IBMM) UMR 5247 CNRS-Université Montpellier-ENSCM, Bâtiment E, Faculté de Pharmacie, 15, avenue Charles Flahault BP14491, 34093, Montpellier, cedex 5, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Menut
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003920:Diabetes Mellitus / Q000188:drug therapy / Q000378:metabolism*; D005681:Gabon; D065089:Glycoside Hydrolase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D016488:Medicine, African Traditional; D010636:Phenols / Q000494:pharmacology* / Q000627:therapeutic use; D008517:Phytotherapy; D024301:Plant Bark; D010936:Plant Extracts / Q000494:pharmacology* / Q000627:therapeutic use; D018515:Plant Leaves; D019666:Rubiaceae / Q000737:chemistry*; D000520:alpha-Glucosidases / Q000378:metabolism*
chemical_list: D065089:Glycoside Hydrolase Inhibitors; D007004:Hypoglycemic Agents; D010636:Phenols; D010936:Plant Extracts; D000520:alpha-Glucosidases