Identification of Bioactive Compounds in Acetone Leaf and Stem-Bark Extracts of Psychotria dalzellii Hook.f. by GC-MS Analysis and Evaluation of in vitro Anti-bacterial Properties

Background: Psychotria dalzellii Hook.f. (Rubiaceae) is an ethnobotanically important plant species, traditionally the stem part is used as a remedy for pruritus and the leaf juice is utilized in the preparation of eye drops for migraines. However, these claims lack of scientific validation. The current study focused on Gas Chromatography-Mass Spectrometry analysis and in vitro evaluation of antibacterial properties of leaf and stem bark acetone extracts of P. dalzellii. Materials and Methods: P. dalzellii leaf and stem-bark samples were collected from Joida, Western Ghats, Karnataka, India. The collected plant materials were subjected to Soxhlet extraction using acetone. The presence of phytochemicals were investigated by preliminary qualitative screening and GC-MS for quantitative estimation. Then, the antibacterial potential was analysed by agar well diffusion technique against selected plant and animal pathogenic bacterial strains. Results: GC-MS chromatogram of acetone stem-bark extract shows the presence of 15 chemical constituents in that, Resorcinol (58.36%) and Hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester (8.81%) were found to be the major phytoconstituents. Whereas, the leaf extract shows 19 bioactive compounds in that, 3,7,11,15-Tetramethyl-2-hexadecen-1-ol (26.99%); Hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl)ethyl ester (21.99%) and Resorcinol (17.87%) were found to be the major compounds. P. dalzellii extracts of stem-bark and leaf exerted greater antibacterial activity towards all tested bacterial strains. Among leaf and stembark extracts, the stembark acetone extract were shown to be the most potent against Gram-negative pathogenic bacterial strains like Pseudomonas syringae (19.33 ± 0.16 mm), Klebsiella pneumoniae (19.25 ± 0.14 mm), Xanthomonas compestris (18.16 ± 0.16 mm) and Escherichia coli (17.25 ± 0.14 mm). Conclusion: This study provides new insights into the Psychotria dalzellii as a potential tool for antibacterial drug discovery through in vitro investigation that could be used to treat human and plant infectious diseases.