Solid-state fermentation with Aspergillus niger for the bio-enrichment of bioactive compounds in Moringa oleifera (moringa) leaves

In recent years solid state fermentation (SSF) has been used to produce bioactive compounds with high added value from agro-industrial waste. This study was aimed to obtain extracts from moringa leaves flour with increased levels of polyphenolic compounds after SSF with Aspergillus niger. Extraction of unfermented and fermented moringa flour was performed using distilled water, 40% acetone (v/v), 80% acetone (v/v), 40% ethanol (v/v) and 80% ethanol (v/v). The highest increases of total phenolics (136.4%) and flavonoids (783.1%) were obtained in fermented flours, with initial moisture of 50 and 70%, respectively when 80% ethanol and 80% acetone were used as extraction solvents, respectively. The 80% acetone extract from fermented flour showed enhanced in vitro antioxidant activity in ferric reduction antioxidant power (277.2 μmol Trolox/g MLF). Extracts from fermented flour exhibited antimicrobial activity against B. subtilis, which was not inhibited by extracts of unfermented flour. Bioactive compounds were identified and quantified using high performance liquid chromatography, and gallic acid was the major compound identified within all extracts. Also, 14 new compounds were released and/or synthesized after flour was fermented. The 80% acetone extract obtained from fermented MLF (50% initial moisture) the highest number of compounds (11), seven of which (epigallocatechin, epigallocatechin gallate, quercetin, kaempferol 3-glycoside, caffeic acid, taxifolin and p-coumaric acid) were not found in the unfermented MLF extract. SSF associated with extraction using organic solvents was successfully used to obtain extracts rich in bioactive compounds and enhanced antioxidant and antimicrobial properties which have potentials in food, cosmetic and pharmacological industries. [Display omitted] •SSF improved the bioactive compounds content in moringa leaf flour extracts.•Novel bioactive compounds (fourteen) were released/produced after fermentation.•Gallic acid, the majority compound, was more concentrated in fermented moringa leaf.•B. subtilis was only sensitive to extracts from fermented moringa leaf.