Exploring a common Apocynaceae - Catharanthus roseus

Alchemica · April 20, 2023

Anyone used the stems/roots of this common ornamental and have experience with it?

The cytotoxic vinca alkaloid constituents are only found in the aerial parts of Catharanthus roseus (Figure 1), the roots are used in several countries as decocts or hot water extracts for the treatment of a number of conditions.

The dried root is an industrial source of ajmalicine (raubasine), which increases the blood flow in the brain and peripheral parts of the body. Preparations of it are used to treat the psychological and behavioural problems of senility, sensory problems (dizziness, tinnitus), cerebrovascular accidents, cranial traumas and their neurological sequelae.

In general, toxicity showed that both extracts and isolated compounds are safe to a certain limit, beyond that they cause adverse effects [1]. That said, the yield of vinblastine and vincristine from C. roseus aerial parts is is low, whereas the precursors, catharanthine and vindoline, are present in higher concentrations [2]. In the stem, there was in micrograms per milligram fresh weight (FW): catharanthine, 0.506 ± 0.044; ajmalicine, 0.071 ± 0.022; serpentine, 0.397 ± 0.031; tabersonine, 0.017 ± 0.003; and vindoline, 0.0026 ± 0.0002 (0.5mg/g fresh weight catharanthine in stem)

Figure 1. The Catharanthus roseus plants used in this paper.

The condensation of catharanthine and vindoline is an absolute requirement for the formation of vinblastine and, later, vincristine. As vindoline is required to synthesise the cytotoxic constituents but does not exist in the roots of C. roseus, but only in the green parts of the plant, no vincristine nor vinblastine can be found in the roots of this species

In the plant, vindoline is a major constituent (up to 0.5%).Major alkaloids in the roots include ajmalicine, catharanthine, and serpentine. Another source mentions ajmalicine and serpentine are essentially present in the roots, whereas catharanthine and vindoline accumulate in aerial parts. The aerial parts contain 0.2-1% alkaloids [3] Roots to be used in pharmacy must contain at least 0.4% ajmalicine and serpentine

Catharanthine (Figure 2) from Catharanthus roseus has been proposed to be a pharmacological treatment for addiction without the adverse side effects associated with ibogaine. It "slows DA reuptake and increases extracellular DA in the nucleus accumbens through partial inhibition of DATs" [4,5] and potentiates GABAARs [6] The root alkaloids from C. roseus root seem to be potent AChE inhibitors and catharanthine exhibited nicotinic receptor antagonism [7]. It has antidepressant activity via SERT inhibition and modulating NE [8]

Figure 2. Catharanthine

Ajmalicine has antihypertensive effects [9]

Experimental: Root material was macerated in basified isopropanol (aq. ammonia) and concentrated to a small sample. TLC (silica, 0.2mm, glass backed, I₂ visualisation) gave poor separation of the constituents with a mixed solvent of acetone:white spirits:1:1. White spirits gave better results with a major constituent Rf = 0.42 and some lesser Rf bands.