A comparative study of the proximate, FTIR analysis and mineral elements of the leaves and stem bark oF Grewia lasiocarpa E.Mey. ex Harv.: An indigenous southern African plant

Abstract

The crude powder of the leaves and stem bark of Grewia lasiocarpa E.Mey. ex Harv., commonly known as forest raisins were analysed for proximate chemical composition (% ash, % carbohydrate, % moisture, % crude lipid, % crude protein and % crude fibre), using the methods of Association of Official analytical chemist (AOAC) and the energy (Kcal) was derived. The FTIR spectrum in the mid-infrared region (4000–400 cm−1) was used for the identification of the different functional groups present. An analytical comparison of the Certified Reference Material (CRM) White Clover (BCR 402) gave a significant correlation between the certified values of the analyte elements (mg Kg−1) and the data obtained using Energy Dispersive X-ray fluorescence (EDXRF) microscopy. The fluorescence characters of the leaves and stem powder were done after treatment with different chemicals.The proximate composition of the ash, carbohydrate, moisture, crude lipid, crude protein and crude fibre (leaves/stem bark) were 33.67 ± 1.04%/24.17 ± 4.25%, 18.75 ± 8.47%/6.74 ± 1.08%, 6.84 ± 3.46%/6.04 ± 0.44%, 2.67 ± 1.15%/2.00 ± 0.00%, 11.93 ± 4.62%/4.25 ± 0.65% and 25.81 ± 2.31%/ 55.59 ± 5.55% while the derived energy values were 146.75 ± 33.56 KCal 100 g−1/61.96 ± 4.07 KCal 100 g−1, respectively. FTIR analysis revealed the presence of functional groups such as C=O, C–H, =C–H, C–O in the leaves and stem bark of G. lasiocarpa, which are responsible for of hemicellulose, alkanes, aromatics, alkynes and carboxylic acid. The EDXRF analysis revealed the presence of elements, including the essential elements such as Calcium (Ca), Iron (Fe), Molybdenum (Mo), Zinc (Zn), Copper (Cu) and Chromium (Cr) in various proportions. The fluorescent analysis revealed varied colours of brown, green, red and purple in the crude powder of G. lasiocarpa E. leaves and stem bark. The results obtained validate the potential use of G. lasiocarpa as a plant with appreciable medicinal and functional food properties although documentation on its ethnobotany is relatively limited.