In vitro antiplasmodial activity, cytotoxicity, and gas chromatography – flame ionization detector metabolites fingerprint of extracts and fractions from Tetrorchidium didymostemon

BACKGROUND: Tetrorchidium didymostemon is used as an antimalarial remedy in southern Nigeria. OBJECTIVE(S): This study was aimed at providing scientific validation for the use of T. didymostemon in the treatment of malaria in Nigeria. MATERIALS AND METHODS: Plasmodium falciparum 3D7 (Pf3D7) strain was cultured and maintained in fresh O(+) human erythrocytes. Standard methods were used to evaluate in vitro antiplasmodial activity, cytotoxic effect on Vero cell line, phytochemical screening, and antioxidant capacity. Gas Chromatography – Flame Ionization Detector (GC-FID) metabolite fingerprinting of the most potent fraction was carried out. RESULTS: The methanol leaf extract had higher antiplasmodial activity (IC(50)Pf3D7 = 25 ± 0.21 μg/mL) in comparison with the stem bark extract (SBE) (IC(50)Pf3D7 = 50 ± 0.94 μg/mL). The n-hexane fraction of the leaf extract had the best antiplasmodial activity (IC(50)Pf3D7 = 3.92 ± 0.46 μg/mL) and selectivity index. This was followed by the dichloromethane (IC(50)Pf3D7 = 12.5 ± 1.32 μg/mL), ethyl acetate (IC(50)Pf3D7 = 35.0 ± 4.80 μg/mL), and hydromethanol fraction which was inactive (IC(50)Pf3D7 > 100 μg/mL). All extracts and fractions were not toxic on Vero cell line (CC(50) > 1000 μg/mL). The n-hexane and dichloromethane fractions had the highest amount of phytochemicals. GC-FID analysis revealed high amounts of kaempferol, α-pinene, camphor, humulene, azulene, and β-caryophyllene in the n-hexane fraction. CONCLUSION: The results of our study validate the traditional use of T. didymostemon in the treatment of malaria in southern Nigeria. They also suggest that the phytoconstituent(s) responsible for the antiplasmodial activity of this plant may be more extractable in non-polar solvents.