Phytochemical investigation of the Neotropical plant Strychnos aff. darienensis

Strychnos darienensis Seem. of the family Loganiaceae, initially identified by Seemann [1], is widely distributed in the region of Central and South America [2] and it was used in the preparation of curarizing arrow poison from the South American Indian hunters. Generally, Strychnos species are rich in alkaloids, whereas the content of other secondary metabolites is in many cases neglected. In continuation of our investigation of plants from the Amazonia [3], S. aff. darienensis that has not been previously investigated was collected from Peru. The evaluation of the best extraction procedure in order to recover a vast range of metabolites was of great importance. Profiling of the extracts with TLC revealed that the best approach was the maceration of the stem bark with EtOAc-EtOH-NH3 (96:3:1) and percolation with EtOAc and then with MeOH [4]. We report herein the investigation of the EtOAc and MeOH extracts, which has lead to the isolation of flavonoids and alkaloids. The isolation procedure was performed using Medium Pressure Liquid Chromatography (MPLC), molecular exclusion chromatography on Sephadex LH-20, semi preparative HPLC and preparative TLC. All compounds isolated, were identified by means of spectral data (1D and 2D NMR, HRMS). Two monomeric flavonoids and one bisflavonoid were identified, namely luteolin (1), 3-methoxyquercetin (2) strychnobiflavone (3) and the monoterpene alkaloid venoterpin. Compound 2 is for the first time reported in the genus and strychnobiflavone (3) is isolated for the second time from a plant extract [5].

Figure 1: Isolated flavonoids of Strychnos aff. darienensis

References: 1 Semmann B (1854) Bot Voy Herald 166, London

2 Krukoff BA (1979) Phytologia 41: 201–238.

3 Vougogiannopoulou et al. (2010) Org Let 12: 1908–1911.

4 Philippe G et al. (2003) Phytochemistry 62: 623–629.

5 Nikoletti M et al. (1984)J Nat Prod 47: 953–957.