Introduction: The seeds of Voacanga Africana Stapf (Apocynaceae), rich in indole alkaloids, is an important non-traditional export commodity in Ghana because the indole alkaloids are a cheaper source of starting material for the production of nootropic and geriatric medicines by some pharmaceutical companies. However, this export trade is limited by the lack of adequate quality control tools locally. This study, therefore, sought to improve the Voacanga trade in Ghana by providing a standard means of chemical quality control for the seeds prior to export.
Method: Six different alkaloids were isolated and purified from the seeds using acid-base fractionation, isocratic column chromatography (silica gel stationary phase and chloroform: ethyl acetate; 60: 40, v/v mobile phase) and recrystallization. The most abundant of the alkaloids was characterized spectroscopically (UV, FT-IR, NMR and MS) and elucidated as coronaridine. An isocratic reverse phase High Performance Liquid Chromatography (RP-HPLC) method (µ-Bondapak C18, 3.9 x 300 mm, 5 µm; water: methanol; 60: 40, v/v; 1.5 mL/min) with UV detection (206 nm) was developed and validated using the coronaridine as a biomarker.
Results and Discussion: The retention time of the biomarker was 2.9±0.03 min. The calibration plot was linear over the concentration range 1.40 µg/mL – 22.40 µg/mL with a coefficient of regression (r) of 0.9996. The Limit of Detection (LOD) and Limit of Quantitation (LOQ) were 0.60 µg/mL and 1.81 µg/mL, respectively. An average recovery of 84.0±5.80 % was obtained, as well as an intra-day and intermediate precision (as measured by the Relative Standard Deviation, RSD) of 1.93 % and 1.65 %, respectively. The proposed method was found as accurate, precise, specific and robust in accordance with ICH guidelines.
Conclusion: A validated simple and economical isocratic RP-HPLC method has been developed for the routine quality control of the seeds of Voacanga africana to boost Ghana’s export trade.