A green method for the extraction of Moringa oleifera leaves: evaluation of several in vitro assays for bioactive properties

Today’s green chemistry is pushing for the search and application of novel methods for the extraction of bioactive ingredients from biomass, which are directly related to human health such as food, pharmaceutics, and cosmetics. Therefore, the purpose of this study is to propose a green extraction method by application of automated solvent extraction from the leaves of Moringa oleifera. Central composite design together with response surface approach was exploited for designing of experimental work, modeling, and optimization reasons. Extraction time (40–60 min), particle size of the leaves (0.5–2 mm), and ethanol (solvent) concentration (30–90%, v/v) were the process factors, which were analyzed statistically by means of central composte design. The best conditions to attain the greatest total phenolic and flavonoid contents (34.201 mg-GAE and 162.349 mg-CE per g dried sample) are 60 min of extraction time, 1.25 mm of particle size and 87% (v/v) ethanol solution. While the most effective parameter in terms of total phenolic substance was extraction time, the most statistically significant variable in terms of flavonoids was solvent concentration. The generated second-order models were satisfactory, which was confirmed by validation study (< 2%). In order to verify the findings of antioxidant activity of the extracts, ABTS and DPPH assays were also conducted. A positive and satisfactory correlation (> 0.80) between test results confirms the accuracy of the results.