Extraction of alkaloids from baobab (adansonia digitata) fruit pulp for the production of antioxidant functional sweets

Abstract

Oxidative stress is a major driver of chronic non-communicable diseases, creating demand for accessible, food-safe antioxidant sources derived from natural plant matrices. The baobab fruit (Adansonia digitataL.) is well established as a rich source of vitamin C and phenolic compounds; however, its alkaloid fraction and potential for incorporation into functional confectionery remain underexplored. This study aimed to extract alkaloids and associated bioactive compounds from dried baobab fruit pulp, characterise them by spectroscopic and phytochemical methods, quantify total alkaloid content, evaluate antioxidant activity, and formulate a functional antioxidant sweet. Dried baobab fruit pulp powder was extracted using an acidified hydroethanolic solvent (70:30 ethanol–water, pH 3–4) via mechanical shaking maceration at 40–60°C. The concentrated extract was characterised by Fourier Transform Infrared (FTIR) spectroscopy and subjected to qualitative alkaloid screening using Mayer’s and Dragendorff’s reagents. Total alkaloid content (TAC) was determined by titrimetric analysis (0.1 N NaOH, methyl red indicator) and expressed as atropineequivalents. Antioxidant activity was assessed qualitatively by the iodine–starch discoloration assay and quantitatively by the Ferric Reducing Antioxidant Power (FRAP) assay. FTIR spectral analysis confirmed the presence of alkaloids, with characteristicabsorption bands at approximately 3300 cm⁻¹ (N–H/O–H stretching), 1630 cm⁻¹ (C=N stretching), and 1050 cm⁻¹ (C–N stretching), consistent with quinoline and indole-type frameworks. Dragendorff’s test produced a weak positive orange-red precipitate, indicating the presence of alkaloids at low concentration, consistent with baobab’s phytochemical profile. TAC was calculated as 16.1% expressed as atropine equivalents (mean of triplicate titrations: 16.4%, 15.9%, 15.9%). Both antioxidant assays returned positive results: the iodine–starch assay confirmed partial decolouration in the crude extract and in the final sweet matrix, and FRAP analysis yielded a mean value of 8.14 mmol Fe²+ per gram of extract (range: 1.92–24.13 mmol/g across 20–100% extract concentrations), demonstrating a clear concentration-dependent response. A functional antioxidant confectionery sweet was successfully produced by incorporating the extract below 80°C into a sugar-glass matrix, with a final product pH of 4.5–5.0, reflecting the natural acidity of baobab pulp. The study demonstrates the feasibility of extracting bioactive alkaloids from baobab fruit pulp and incorporating them into a functional food product while retaining measurable antioxidant activity.