Medicinal plants are the richest, cheapest and most readily available source of drugs, nutraceuticals and food supplements. Pharmaceutical industries still rely largely on medicinal plants for intermediates due to their chemical diversities. This study, therefore, investigated the chemical constituents, thermal decomposition products and biological activities of extract from seeds of Cola nitida (the ‘kola nut’).
The pulverized seed was sequentially extracted with dichloromethane and methanol CH3OH. The extracts were analysed directly by Fourier Transform Infra-Red, electrospray ionization mass spectrometer and as fatty acid methyl ester and trimethylsilyl derivatives by gas chromatography-mass spectrometry (GC-MS). The CH3OH extract was analysed by high-performance liquid chromatography for sugars. The intact and extracted seed biomasses were analysed directly by pyrolysis GC-MS. For isolation of chemicals and assessment of biological activity, a large scale CH3OH extraction was performed and the extract partitioned with n-hexane, ethyl acetate (EtOAc) and butanol. Fractionation was done using various chromatographic techniques. Antimicrobial and antioxidant activities of the extract, fractions and isolated caffeine were respectively determined by the methods of agar-well diffusion and 2,2-diphenyl-1-picrylhydrazyl radical scavenging.
Caffeine and hexadecanoic acid were isolated from the EtOAc fraction while theobromine, caffeine, catechins, procyanidins, proanthocyanidins, sugars, fatty acids, alcohols and sterols were identified in the extracts. Multitude (62) biomass degradation products were identified in pyrolysed seed samples. The extract and fractions showed varying activities against most of the tested microbes, except against Shigella species, for which neither the extract nor fractions elicited any response. The butanol fraction exhibited the highest antioxidant activity.
This report gives insight into the chemical constituents in Cola nitida seed, details the thermal decomposition constituents and establishes the antimicrobial and antioxidant activities of the seed extract and fractions, thereby contributing to the knowledge on the chemistry and pharmacology of the genus.
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