Quinoline, Indole, and Isogranatanine Alkaloids from Malayan Leuconotis eugeniifolia

  • J Nat Prod. 2024 Feb 23;87(2):286-296. doi: 10.1021/acs.jnatprod.3c00960.
Yi-Sheng Tan  1 ,  Min-Phin Ng  2 ,  Chun-Hoe Tan  3 ,  Wai-Kit Tang  1 ,  Kae-Shin Sim  2 ,  Kien-Thai Yong  2 ,  Premanand Krishnan  4 ,  Kuan-Hon Lim  5 ,  Siew-Huah Lim  1 ,  Yun-Yee Low  1
Affiliations
  • 1. Department of Chemistry, Faculty of Science, Universiti Malaya, 50603 Kuala Lumpur, Malaysia.
  • 2. Institute of Biological Sciences, Faculty of Science, Universiti Malaya, 50603 Kuala Lumpur, Malaysia.
  • 3. Department of Biotechnology, Faculty of Applied Science, Lincoln University College, 47301 Petaling Jaya, Selangor, Malaysia.
  • 4. Foundation in Science, University of Nottingham Malaysia, Jalan Broga, 43500 Semenyih, Selangor, Malaysia.
  • 5. School of Pharmacy, University of Nottingham Malaysia, Jalan Broga, 43500 Semenyih, Selangor, Malaysia.
PMID: 38284153 DOI: 10.1021/acs.jnatprod.3c00960
Abstract

Nine new Alkaloids, eugeniinalines A-H (1-8) and (+)-eburnamenine N-oxide (9), comprising one quinoline, six indole, and two isogranatanine Alkaloids, were isolated from the stem-bark extract of the Malayan Leuconotis eugeniifolia. The structures and absolute configurations of these Alkaloids were established based on the analysis of the spectroscopic data, GIAO NMR calculations, DP4+ probability analysis, TDDFT-ECD method, and X-ray diffraction analysis. Eugeniinaline A (1) represents a new pentacyclic quinoline alkaloid with a 6/6/5/6/7 ring system. Eugeniinaline G (7) and its seco-derivative, eugeniinaline H (8), were the first isogranatanine Alkaloids isolated as natural products. The known Alkaloids leucolusine (10) and melokhanine A (11) were found to be the same compound, based on comparison of the spectroscopic data of both compounds, with the absolute configuration of (7R, 20R, 21S). Eugeniinalines A and G (1 and 7) showed cytotoxic activity against the HT-29 Cancer cell line with IC50 values of 7.1 and 7.2 μM, respectively.