Multi-solvent extraction, quantification and characterisation of tannin from <i>Neltuma juliflora</i> bark: a pathway to sustainable utilisation

This research investigates the extraction, quantification and characterisation of tannin from the bark of <i>Neltuma juliflora</i> (Sw.) Raf. (<i>N. juliflora</i>, formerly known as <i>Prosopis juliflora</i> (Sw.) DC.), an invasive species that is widely available but underutilised. Various solvent extraction techniques, including single-phase, combined and sequential extractions, were evaluated. The highest tannin yield (85%) was obtained with 4% NaOH in single-phase extraction, while combined extraction resulted in the highest tannin purity (85.91%). Sequential extraction demonstrated solvent selectivity, with methanol producing the highest extract (93.6%) and acetone yielding a highly purified fraction (83.14%). The presence of essential tannin functional groups was validated by Fourier Transform Infra-red (FTIR) spectroscopy. The analysis of band gap energy indicated values between 4.00 and 5.09 eV, varying with the extraction method. These findings underscore <i>N. juliflora</i> as a promising sustainable tannin source, which offers an eco-friendly alternative to conventional sources and supports invasive species control efforts.