Organic and Mineral Composition of Seeds of Afrostyrax lepidophyllus Mildbr. and Evaluation of ROS Inhibition and Cytotoxicity of Isolated Compounds

Abstract

Considering the large consumption of Afrostyrax Lepidophyllus seeds, chemical analyses is necessary to ascertain its use as food spice and also its medicinal potential. Inductively coupled plasma mass spectrometry and gas chromatography mass spectrometry were used to evaluate the mineral and volatile contents respectively while column chromatography enabled the isolation of some compounds. Seventeen compounds were identified by gas chromatography mass spectrometry. Amongst detected sulphur containing compounds, methylsulfinyl(methylthio) methane was in highest amount with percentage composition of 12.25%. Fatty acids and their methyl esters were most abundant constituents notably n-hexadecanoic acid (28.86%) and methyl (E)-9-octadecenoate (21.85%). Some important unsaturated fatty acids notably linoleic acid and oleic acid were identified. Major elements detected in the sample were sodium (42,137.57 ppb), magnesium (456.90 ppb), phosphorus (1703.31 ppb), potassium (4948.88 ppb) and calcium (88.37 ppb. Trace elements detected in the sample are Cr (0.81 ppb), Mn (5.66 ppb), Fe (107.08 ppb), Co (0.14 ppb), Ni (6.77 ppb), Cu (50.05 ppb), Zn (32.06 ppb) and B (6.65 ppb). Other detected elements involved Al (42.25 ppb) and Pb (2.63 ppb) while Cd and Hg were below detectable limits. Five compounds were isolated and identified from their NMR spectral data as tripalmitin (AL23), n-hexadecanoic acid (AL40-45), ursolic acid (AL65), stigmasterol glycoside (AL192) and saccharose (AS329). Ursolic acid showed moderate ROS inhibition with IC50 = 18.5 ± 3.1 µg/mL compared to 11.2 ± 1.9 µg/mL for ibuprofen. NO inhibition and cytotoxicity on NIH-3T3 cell lines were low for tested compounds. This study fills knowledge gap on chemical analyses of A. lepidophyllus.