Constituíntes químicos de Tabernaemontana laeta Mart. (Apocynaceae) (Vols. 1 e 2)

Abstract

The family Apocynaceae is specially known for the bioproduction of indole alkaloids, Many species of this family are used since old times in popular medicine and in mystic rituals, and nowadays several species are used as natural source of substances of scientific and economic interest, mainly for the pharmaceutical industry. Among the genera of this family, Tabernaemontana stands out for the great variety and number of monoterpenoid indole alkaloids. The purpose of this work seeks was the phychemical investgation of the barks of the roots, leaves, fruits and seeds of the species Tabernaemontana laeta Mart. During this study twenty-five substances were isolated: eight monoterpenoid indole alkaloids with an ibogan skeleton: coronaridine (1), voacangine (2), isovoacangine (3), 19-(S)-heyneanine (4), isovoacristine (5), 3- oxoisovoacangine (6), ibogaine (7) and iboxygaine (8); one with a plumeran skeleton: tabersonine (9); one with an aspidospermatan skeleton: apparicine (10); two with a corynanthean skeleton: vobasine (11) and Nb-methylvoachalotine (12); three bis-indole alkaloids: voacamine (13), conodurine (14) and tabernamine (15); eight triterpenes, of which seven pentacyclic: 3ß-O-acetyl-urs-20-en-22-one (16), 3ß-O-acetyl-D-friedours- 14-en-16-one (17), 313 -O-acetyl-urs-12-en-1ß, l lct-diol (18), 3ß -O-acetyl-a-amyrin (20), 3ß-O-acetyl- ß-amyrin (21), 313-O-acetyl-lupeol (22) and 3-O-acetyl-taraxerol (23) and one tetracyclic with dammarane skeleton: 3ß-O-acetyl-20,24-epoxydammarane (19) and two sterols: ß-sitosterol (24) and 3ß-O-D-glicopyranosil-ß-sitosterol (24). Among these substances the alkaloid 12 and the triterpene 19 were new natural products. The isolated substances were identified through their spectral data, especially NMR. The full assignment of the spectra led in several cases to the correction of previously published assignments