Evaluation of the mineral composition, phytochemical and proximate constituents of three culinary spices in Nigeria: a comparative study

Spices are prolific sources of phytochemicals of pharmaceutical and nutritional importance. They have been employed for centuries in the treatment of various maladies, in cuisines, and as inhibitors of oxidative degradation in foods. On this premise, a comparative assessment of the quantitative mineral composition, phytochemical and proximate constituents of Xylopia aethiopica (fruits), Piper guineense (seeds), and Rhaphiostylis beninensis (roots) was done using standard protocols. Subsequently, methanol extracts of the spices were subjected to Gas Chromatography–Mass Spectrometry (GC–MS) analysis. Mineral analysis of the culinary spices revealed significant differences (p < 0.05) in the spices’ magnesium, zinc, iron, selenium, copper, calcium, manganese, molybdenum, potassium, and sodium contents. In the phytochemical analysis, flavonoids, phenols, and alkaloids (4.04%, 2.92%, 2.23%) predominate in X. aethiopica. Similarly, proximate analysis shows a preponderance of carbohydrates (81.24%) and proteins (4.83%) in R. beninensis and P. guineense respectively. However, values for the selenium (0.25 mg/L), saponin (0.23%), and moisture (0.71%) contents for R. beninensis were the lowest among the three spices. Results from the GC–MS analysis revealed the presence of thirteen, twelve, and thirteen phytoconstituents of X. aethiopica, P. guineense, and R. beninensis respectively. Prominent among them are hydrocarbons, acids, and esters with renowned biological attributes such as antioxidant, antimicrobial and anti-inflammatory. These findings indicate that the spices are notable wellsprings of bioactive components and justify their plethoric applications in Nigeria. Therefore, they could serve as lead compounds in the search for natural ingredients for drugs and nutraceuticals formulation.