African locust bean (Parkia biglobosa) seed coat: A source of phenolic compounds

Abstract

Parkia biglobosa is a versatile plant species used extensively by local communities in arid Africa. The seeds of this plant are valued for their high polyphenol content, highlighting their therapeutic antioxidant, and anti-inflammatory, antimicrobial, antidiabetic and antihypertensive properties. The aim of this study was to optimize the conditions for the extraction of the polyphenol content of the seed coat of P. biglobosa. Five extraction factors, namely solvent concentration, time, temperature, solid-liquid ratio, and pH, were optimized using the response surface technique. The optimization screening design results showed that temperature, time and solvent concentration were the most important variables with significant effects on polyphenol yield in a two-stage Placket-Burman design (p0.05). Box Behnken and Response Surface Analysis were applied to further investigate the mutual interactions between these variables and determine the ideal values that give the highest possible phenolic yield. The results showed the following ideal extraction conditions: 45 °C temperature, 240 min extraction time and 47.5 % solvent concentration. The TPC value obtained under the ideal extraction conditions was 54.023 ± 2.05 mg GAE /g. The antioxidant activity results of the concentrates showed 72.389 % inhibition of 2, 2-diphenyl-2-picrylhydrazyl hydrate and antioxidant capacity of 80.96 ± 1.16 mg AA /g. The results of the study show that the model is suitable for maximizing polyphenol extraction from the dried seed coat of P. biglobosa, as there is good agreement between the laboratory experiments and the estimated values