A new procyanidin B from Campylospermum zenkeri (Ochnaceae) and antiplasmodial activity of two derivatives of (±)-serotobenine

Abstract

Phytochemical investigation of the stem bark of Campylospermum zenkeri led to the isolation of five known compounds: (Z,Z)-9,12-octadecadienoic acid (1), serotobenine (2), agathisflavone (3), lophirone A (4) and lophirone F (5), together with a new derivative of procyanidin B, a catechin dimer named zenkerinol (6). Serotobenine (2) is structurally related to decursivine which shows moderate activity against D6 and W2 strains of Plasmodium falciparum. For a better understanding of structure-activity relationships, three new semi-synthetic derivatives of serotobenine (2) have been prepared. These are: serotobenine monopropionate (2a), serotobenine monopivalate (2b) and serotobenine cyclohexyl ether (2c) respectively. Two of them (2a) and (2b), were evaluated for their antiplasmodial activity against P. falciparum 3D7 strain in a parasite lactate-dehydrogenase (pLDH) assay. Compound 2b was more active than compound 2a based on their IC₅₀ values (36.6 and 123 μM, respectively).

Keywords:

• Campylospermum zenkeri
• Ochnaceae
• zenkerinol
• flavonoids
• serotobenine
• hemisynthesis
• antiplasmodial activity

Acknowledgements

We gratefully acknowledge the DAAD/STIBET Doktoranden Scholarship for financial support and travel grants for Mr. Mbabi to Germany. The authors are also grateful to the Philipps-Universität Marburg, the Chemistry Department and the Koert’s Group for technical assistance. We also thank Mr. Fulbert Tadjouteu (National Herbarium of Cameroon) for his assistance in the collection and identification of the plant material.