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Structure Elucidation of pure Glycosidic Diterpene compound Isolated from the Root of Launaea secunda Hook.(Dauk-khwa)
- In this PhD research work, one Myanmar indigenous medicinal plant, namely Launaea secunda Hook. (Dauk-khwa) was selected for chemical analysis. Firstly, preliminary phytochemical screening of selected plant was performed. According to the phytochemical test, the root of Dauk-khwa contains alkaloid, steroid, terpene, sugar, glycoside, phenolic and polyphenol respectively. Moreover, antimicrobial activities of the crude extract of root of this plant in various solvent systems were tested by agar well diffusion method on six organisms, such as Bacillus subtilis, Staphylococcus aureus, Bacillus pumalis, Pseudomonas aeruginosa, Candida albican and Mycobacterium species. The ethyl acetate extract of the root of Dauk-khwa responds high antimicrobial activities on all selected organisms. A bioactive organic compound (MMK-1) was isolated from the root of Launaea secunda Hook. (Dauk-khwa) by using Thin Layer and Column Chromatographic methods. Pure yellowish brown oily form compound (22.0 mg) was obtained and the yield percent was found to be (1.162%) based upon the ethylacetate crude extract. This pure compound gives positive for terpene and glycoside tests. The antimicrobial activities of isolated pure compound were rechecked by agar well diffusion method on six selected organisms and this pure compound gave medium activities on five tested organisms except Bacillus subtilis. In addition, the molecular formula CC26H44o6) and the complete planar structure of compound (MMK-1 ) were elucidated by spectroscopic methods such as FT-IR, 1H NMR (500 MHz),13C NMR (125 MHz), DEPT, HMQC, HMBC, DQF-COSY and FAB mass spectral data. Finally, conformational structure and absolute configuration containing (10) chiral carbons of compound (MMK-1) was determined by using 1H NMR, splitting patterns, coupling constant (J-values), NOESY spectral data and model studies. The IUPAC name of elucidated pure compound is (2R, 3S, 4S, SS, 6S)-2-((2S, 4aS, 4bS, 7S, l0aR)-7-ethyl-1, 1, 4a, 4b-tetramethyl-1, 2, 3, 4, 4a, 4b, 5, 6, 7, 9, 10, 10a-dodecahydro- phenanthren-2-yloxy)-6-(hydroxymethyl)tetrahydro-2H-pyran -3,4,5-triol.
Myint Myint Khaing