1. Carboline Alkaloids

2. 1- Rauwolfia Alkaloids  Source: Rauwolfia roots (Rauwolfia serpentina, Fam. Apocynaceae)

3.  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".

4.  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 (250-500 mg daily) and as tranquilizers (0.1- 1mg or more daily).

5. 2- Yohimbe Alkaloids  Source: Yohimbine occurs in the barks of the West African tree Pausinystalia yohimbe = Coryanthe yohimba, Fam. Rubiaceae.

6.  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.