Tecoma stans: Alkaloid profile and antimicrobial activity

• Published in: Journal of pharmacy & bioallied science 2019-10, Vol.11 (4), p.341-347
• Main Authors: Bakr, Riham, Fayed, Marwa, Salem, Mohammad, Hussein, Ahmed
• Format: Article
• Language: English
• Subjects: Alkaloid; Alkaloids; Amino acids; Ampicillin; Analysis; Anti-infective agents; antibacterial; Antifungal activity; Antimicrobial activity; Antimicrobial agents; Bacteria; Binding sites; Chromatography; Dihydropteroate synthase; Flavonoids; Gentamicin; Gram-positive bacteria; Hydrogen bonds; Ligands; Medical research; Medicine, Experimental; Minimum inhibitory concentration; molecular docking; NMR; Nuclear magnetic resonance; Original; Penicillin; Penicillin-binding protein; Plant extracts; Silica; Silica gel; Tecoma stans
• ISSN: 0975-7406; 0976-4879; 0975-7406
• DOI: 10.4103/jpbs.JPBS_79_19

Aim: Tecoma stans (L.) Kunth is a promising species in the trumpet creeper family Bignoniaceae. This study aimed at showing the antibacterial and antifungal potentials of T. stans methanolic leaf extract (TSME) correlated to its phytoconstituents. Materials and Methods: The antimicrobial potential of TSME was evaluated using agar diffusion method. The main alkaloids were separated on silica gel column and identified using nuclear magnetic resonance spectral analysis. Molecular docking was performed for the isolated compounds against MurD ligase, penicillin-binding protein, and dihydropteroate synthase enzyme to rationalize the observed antibacterial effect. Results and Discussion: TSME showed significant antibacterial effect against all tested microorganisms with comparable minimum inhibitory concentration (MIC) to the ampicillin and gentamicin with MIC values ranging between 0.98 and 1.95 µg/mL, in addition to a promising antifungal effect when compared to amphotericin with MIC values 3.9 and 15.63 µg/mL for Aspergillus flavus and Candida albicans, respectively. Several alkaloids were separated, purified, and identified as tecostanine, 4-OH tecomanine, 5-hydroxyskytanthine, and tecomanine, which were previously isolated from T. stans. The docking study showed that the alkaloids bind in a similar fashion to the co-crystallized ligands of the crystal structures of MurD ligase. The binding poses and scores in the case of penicillin-binding protein and dihydropteroate synthase did not match the co-crystallized ligands in their crystal structures. The in silico results suggest an antibacterial mechanism that involves the inhibition of MurD ligase. Conclusion: T. stans alkaloids could represent the basic skeleton for a powerful antimicrobial agent.