Enrique Wenceslao Coronado-Aceves1, Giulia Gigliarelli2, Adriana Garibay-Escobar3, Ramón Enrique Robles Zepeda3, Massimo Curini2, Jaime López Cervantes4, Clara Inés Inés Espitia-Pinzón5, Stefano Superchi6, Stefania Vergura6, Maria Carla Marcotullio7. 1. Department of Chemistry-Biology, University of Sonora, Blvd. Luis Encinas y Rosales s/n, Hermosillo, Sonora 83000, Mexico; Department of Biotechnology and Alimentary Sciences, Technological Institute of Sonora, 5 de Febrero 818 Sur, 85000 Ciudad Obregon, Sonora, Mexico. 2. Department of Pharmaceutical Sciences, University of Perugia, via del Liceo, 1-06123 Perugia, Italy. 3. Department of Chemistry-Biology, University of Sonora, Blvd. Luis Encinas y Rosales s/n, Hermosillo, Sonora 83000, Mexico. 4. Department of Biotechnology and Alimentary Sciences, Technological Institute of Sonora, 5 de Febrero 818 Sur, 85000 Ciudad Obregon, Sonora, Mexico. 5. Immunology Department, Biomedical Research Institute, National Autonomous University of Mexico, 04510 DF, Mexico, Mexico. 6. Department of Sciences, University of Basilicata, Via dell'Ateneo Lucano 10, 85100 Potenza, Italy. 7. Department of Pharmaceutical Sciences, University of Perugia, via del Liceo, 1-06123 Perugia, Italy. Electronic address: mariacarla.marcotullio@unipg.it.
Abstract
ETHNOPHARMACOLOGY RELEVANCE: The evaluation of the antimycobacterial activity of extracts of medicinal plants used by Mayos against tuberculosis and respiratory problems, allowed the identification of Rhynchosia precatoria (Humb. & Bonpl. ex Willd.) DC (Fabaceae) as the best candidate to find new antimycobacterial compounds. AIM OF THE STUDY: To isolate and characterize the compounds of R. precatoria responsible for the inhibitory and bactericidal activity against Mycobacterium tuberculosis H37Rv and Mycobacterium smegmatis ATCC 700084. To determine antimycobacterial synergistic effect of pure compounds and their selectivity index towards Vero cells. MATERIALS AND METHODS: A total of six flavonoids were purified by silica gel column chromatography. Structural elucidation of the isolated compounds was achieved by using 1D and 2D NMR spectroscopy techniques. The configuration at the C-3 chiral center was established by quantum mechanical calculation of the electronic circular dichroism (ECD) spectrum. In vitro inhibitory and bactericidal activity against M. tuberculosis and M. smegmatis were determined with the redox indicator Alamar Blue (resazurin). Synergy was determined by X/Y quotient. Cytotoxicity was measured by MTT assay. RESULTS: The isolated compounds were identified as precatorin A (1), precatorin B (2), precatorin C (3), lupinifolin (4), cajanone (5) and lupinifolinol (6). Compounds 1-3 are new. Compounds 1 to 5 inhibited the growth of M. tuberculosis (MIC ≥31.25µg/mL); compounds 1, 2, 4 and 5 killed the bacteria (MBC ≥31.25µg/mL) and also inhibited M. smegmatis (MIC ≥125µg/mL), while 1 and 4 also resulted bactericidal (MBC ≥125µg/mL). Compounds 4 and 5 presented synergistic effect (X/Y quotient value <0.5) at a concentration of 1/2 MIC of each compound in the combination. Cytotoxicity in murine macrophages (RAW 264.7 cells) gave IC50 values of 13.3-46.98µM, for compounds 1-5. CONCLUSIONS: In this work we isolated two new isoflavanones (1 and 2), and one new isoflavone (3) with a weak antimycobacterial activity. The (3R) absolute configuration was assigned to 1 by computational analysis of its ECD spectrum and to 2 and 5 by similarity of their ECD spectra with that of 1. We are also reporting by first time, activity against virulent strain of M. tuberculosis for compounds 4 and 5 and their antimycobacterial synergistic effect.
ETHNOPHARMACOLOGY RELEVANCE: The evaluation of the antimycobacterial activity of extracts of medicinal plants used by Mayos against tuberculosis and respiratory problems, allowed the identification of Rhynchosia precatoria (Humb. & Bonpl. ex Willd.) DC (Fabaceae) as the best candidate to find new antimycobacterial compounds. AIM OF THE STUDY: To isolate and characterize the compounds of R. precatoria responsible for the inhibitory and bactericidal activity against Mycobacterium tuberculosis H37Rv and Mycobacterium smegmatis ATCC 700084. To determine antimycobacterial synergistic effect of pure compounds and their selectivity index towards Vero cells. MATERIALS AND METHODS: A total of six flavonoids were purified by silica gel column chromatography. Structural elucidation of the isolated compounds was achieved by using 1D and 2D NMR spectroscopy techniques. The configuration at the C-3 chiral center was established by quantum mechanical calculation of the electronic circular dichroism (ECD) spectrum. In vitro inhibitory and bactericidal activity against M. tuberculosis and M. smegmatis were determined with the redox indicator Alamar Blue (resazurin). Synergy was determined by X/Y quotient. Cytotoxicity was measured by MTT assay. RESULTS: The isolated compounds were identified as precatorin A (1), precatorin B (2), precatorin C (3), lupinifolin (4), cajanone (5) and lupinifolinol (6). Compounds 1-3 are new. Compounds 1 to 5 inhibited the growth of M. tuberculosis (MIC ≥31.25µg/mL); compounds 1, 2, 4 and 5 killed the bacteria (MBC ≥31.25µg/mL) and also inhibited M. smegmatis (MIC ≥125µg/mL), while 1 and 4 also resulted bactericidal (MBC ≥125µg/mL). Compounds 4 and 5 presented synergistic effect (X/Y quotient value <0.5) at a concentration of 1/2 MIC of each compound in the combination. Cytotoxicity in murine macrophages (RAW 264.7 cells) gave IC50 values of 13.3-46.98µM, for compounds 1-5. CONCLUSIONS: In this work we isolated two new isoflavanones (1 and 2), and one new isoflavone (3) with a weak antimycobacterial activity. The (3R) absolute configuration was assigned to 1 by computational analysis of its ECD spectrum and to 2 and 5 by similarity of their ECD spectra with that of 1. We are also reporting by first time, activity against virulent strain of M. tuberculosis for compounds 4 and 5 and their antimycobacterial synergistic effect.
Authors: Ali A Rabaan; Saad Alhumaid; Hawra Albayat; Mohammed Alsaeed; Fadwa S Alofi; Mawaheb H Al-Howaidi; Safaa A Turkistani; Salah M Alhajri; Hejji E Alahmed; Abdulwahab B Alzahrani; Mutaib M Mashraqi; Sara Alwarthan; Mashael Alhajri; Fatimah S Alshahrani; Souad A Almuthree; Roua A Alsubki; Abdulmonem A Abuzaid; Mubarak Alfaresi; Mona A Al Fares; Abbas Al Mutair Journal: Molecules Date: 2022-08-22 Impact factor: 4.927