A sustainable extraction procedure for indole alkaloids from Vinca minor

Monoterpene indole alkaloids (MIA) comprise a large subgroup of alkaloids with diverse biological activities [1] [2]. MIA enriched fractions are usually obtained by acidic or basic extraction of plant material, followed by two-step liquid-liquid extractions (LLE) using hydrochloric acid and dichloromethane (DCM) or chloroform as the most common solvents [3]. However, DCM and chloroform have been classified as hazardous substances due to their severe detrimental effects on health and the environment. The aim of the study was therefore; to improve the extraction procedure for MIA using solvents generally recognised as sustainable [4].

The experiments were performed using aerial parts of Vinca minor L., a well-known Apocynacea in Europe. For LLE after acidic extraction (pH 1), DCM was replaced by ethyl acetate (EtOAc) or n-butyl acetate. The alkalinized aqueous phase was then re-extracted in DCM, EtOAc or heptane. For alkaline extraction, an equal volume of DCM, n-butanol, EtOAc or heptane was added to the aqueous solution (pH 9). Organic partitions were subsequently extracted with citric acid (pH 1), which was then re-extracted using DCM, EtOAc or heptane after alkalinization (pH 9). The success of each procedure was estimated at analytical scale by HPLC, comparing the content of the reference compound vincamine in the organic phases obtained from the second step of LLE.

Overall, with exception of n-butanol, all solvents replacing DCM were at least as efficient in enriching MIA, particularly EtOAc performed superiorly. The current study is therefore an encouraging example how principles of green chemistry can easily be introduced in routine phytochemical practice.

 

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• References

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Publication History

Article published online:
16 November 2023