Abstract

Polypharmacological activities of the biflavonoid fraction of Garcinia kola seed justify its development as a nutraceutical, however, quality assurance of active nutraceutical ingredient (ANI) requires conformance to appropriate standards of composition and quality. It was hypothesized that variation in extraction protocols, as previously reported for the biflavonoid fraction, would lead to variation in extract composition and potency. Computational antioxidant capacity simulation (CAOCS) assay of G. kola extracts obtained by different extraction protocols tested the hypothesis, through incremental addition (250 and 100 µL) of standard antioxidant (AOX) extract solutions in a photometric titration. Preferred model fitting was then statistically selected between mono- and bi-exponential decay. Best - fit reaction constant (k_ptt) was integrated into a metric for ranking antioxidant capacity (AOC) of the extracts. The AOC metric is a molecular descriptor for kinetics of phenolic bond cleavage. Three AOX extracts, namely, ethyl acetate seed extract, kolaviron and acetone seed extract were found to vary in composition, and produced optimal AOC values of 1500/g, 1150/g, and 1050/g respectively. Our findings demonstrated that the composition and potency of biflavonoid fraction of G. kola seed are critically dependent on solvent extraction protocol, and hence, consistent with the hypothesis. CAOCS assay is a suitable analytical tool for ensuring batch–to–batch sameness of ANI prepared from G. kola seed.

Key words: Garcinia kola seed extracts, biflavonoids, active nutraceutical ingredient, antioxidant capacity, quality assurance.

Abbreviation

AICc, Akaike's information criterion; ANI, active nutraceutical ingredient; AOC, antioxidant capacity; AOX, antioxidant; ASE, acetone seed extract; BED, bi-exponential decay; CAOCS, computational antioxidant capacity simulation; DSP, Digital signal processing; EASE, ethyl acetate seed extract; KV, kolaviron; MED, mono-exponential decay; PPA, photometric phenolphthalein assay; PPRA, photometric phenol red assay; PTKM, proton transfer kinetics modeling; TLC, thin layer chromatography.