Optimisation of total flavonoids and total antioxidants extraction from dacryodes edulis leaves

Aim: The aim of this study is to apply experimental design to optimize extraction of total flavonoid and total antioxidant from Dacryodes edulis leaves. Study Design: D. edulis leaves were collected from March to April 2016 around Agboville in the southern part of Cote d’Ivoire. Afterwards, the leaves were transferred to the laboratory for drying. Place and Duration of Study: This study was carried out from June to July 2016 in the Chemistry Laboratory of Water and Natural Substances, at Felix Houphouet Boigny National Polytechnic Institute of Yamoussoukro, Cote d’Ivoire. Methodology: The harvested leaves were subdivided in two groups (Group 1 and Group 2). The leaves of Group 1 were dried in an oven at 40 ° C for 5 days and those of Group 2, dried in the shade for 2 weeks. Then the effect of 5 parameters (solid-liquid ratio, drying method, extraction solution, extraction time and the extraction mode) was observed on the extraction of total flavonoids and total antioxidants. For this purpose, we used two experimental designs: Plackett-Burman design used to identify the most important variables which influence the extraction process and the full factorial design (2k, k = 3), used to optimize the extraction conditions. Results: Results showed that the ratio (w/v), the drying mode and the extraction mode had significant effects on the extraction of total flavonoids and total antioxidants from D. edulis leaves. The optimal experimental conditions for the highest amount of total flavonoids and total antioxidants are obtained through aqueous maceration from dried leaves of D. edulis in oven for 60 minutes with a solid-liquid ratio of 1/100 (w/v). The optimized sample presented a total flavonoid content of 100.33± 1.53 mg/g EQ for antioxidant activity of 314.81 ± 11.33mg/g TE. These experimental results were very close to the predicted values.It was observed that total flavonoids showed a good correlation with total antioxidants of the sample. Conclusion: The extraction of total flavonoids and total antioxidants from D. edulis leaves are influenced by the ratio (w/v), the drying method and the extraction mode. Their optimal extraction condition is the maceration in water of D. edulis leaves that have been dried in oven for 60 min with a solid-liquid ratio of 1/100 (w/v). We came across a strong correlation between total flavonoids and total antioxidants. The good antioxidant capacity of the aqueous extract of D. edulis leaves could play an important role for the population in the fight against diseases related to oxidative stress.