Carboline Alkaloids
1- Rauwolfia Alkaloids Source: Rauwolfia roots (Rauwolfia serpentina, Fam. Apocynaceae)
Constituents: The most important are Reserpine and Rescinnamine. Properties: Reserpine and related alkaloids are weakly basic diester, tertiary alkaloids and possess a carboxylic group on ring "E".
Alkaline Hydrolysis: 1- Reserpine → reserpic acid + trimethoxybenzoic acid + methanol. 2- Recinnamine → reserpic acid + trimethoxycinnamic acid + methanol. Its solution acquires a yellow color and a pronounced fluorescence especially after the addition of acids or upon exposure to light. Tests for reserpine: Vanillin /HCl reagent: → violet color. Sodium molybdate in H 2 SO 4 → Yellow → Blue in two minutes. Uses: Reserpine and the related alkaloid rescinnamine are mainly used as antihypertensives ( mg daily) and as tranquilizers (0.1- 1mg or more daily).
2- Yohimbe Alkaloids Source: Yohimbine occurs in the barks of the West African tree Pausinystalia yohimbe = Coryanthe yohimba, Fam. Rubiaceae.
Constituents: About 6% total alkaloids, the major is Yohimbine. Tests: 1- Yohimbine + H 2 SO 4 + crystals of K 2 Cr 2 O 7 → violet streaks → blue → green 2- Yohimbine + Mandalin's reagent → blue color → green Uses: Yohimbine is mainly used as an aphrodisiac drug.