Structural characterization and in vitro biological exploration of phytoconstituents isolated from a chloroform extract of Rauvolfia vomitoria (Apocynaceae) root bark from Côte d’Ivoire

The species of the genus Rauvolfia are a reservoir of indole alkaloids with proven pharmacological properties. A chloroform extract of the root bark of Rauvolfia vomitoria (Apocynaceae) was studied. The phytochemical investigation of said extract allowed the isolated of four indolic alkaloids, three of which are known (Reserpine, ajmaline and mauiensine) and the unknown phyto-constituent (3). In addition, the methyl esters of 3, 4, 5-trimethoxybenzoic acid (Phytoconstituent (1)) and 3, 4, 5-trimethoxycinnamic acid (Phytoconstituent (2)) were characterized and considered as new products of reserpine degradation. Their molecular structures were determined by MS, NMR (H, C), IR, UV and their melting points were established. The evaluation of the antioxidant activity in vitro revealed the antioxidant efficiency expressed by the DPPH radical reduction concentration at 50% (CR50) of the phytoconstituents (3) (CR50= 0.346 mg/mL) and (5) (CR50= 0.127 mg/mL) compared with vitamin C (CR50 = 0.003 mg/mL). The in vitro study of the anticholinesterase activity towards galantamine, showed a clear anticholinesterase activity with percentages of acetylcholinesterase inhibition higher than 50% of the phytoconstituents (4) and (5). Moreover, phyto-constituent (5) showed the best antioxidant and anticholinesterase activity. These results presage promising research, including toxicological evaluation for therapeutic phyto-formulations.