Morinda citrifolia L. leaves extracts obtained by traditional and eco-friendly extraction solvents: Relation between phenolic compositions and biological properties by multivariate analysis

Morinda citrifolia L. leaves (MCLs) have attracted considerable interest in the agricultural, pharmaceutical, and food industries owing to its medicinal properties. This present work aims to investigate the influences of extraction solvents such as water, organic solvents (ethanol, methanol, acetone, and ethyl acetate) and eco-friendly deep eutectic solvents (DESs) on total phenolic content (TPC), total flavonoid content (TFC), biological properties, and antimicrobial activity of MCLs extracts. Results indicated that the MCLs extracts extracted by three types of DESs exhibited the highest TPC (25.17–30.93 mg GAE/g DW), while that extracted by ethyl acetate as extraction solvent had the lowest TPC and TFC. Phenolic compositions of the MCLs extracts were identified and quantified by HPLC-ESI-QTOF-MS/MS. Among them, gallic acid, orientin, rutin and ferulic acid were the dominant components in the MCLs extracts obtained by different solvents. In addition, the three DESs also showed more excellent performances on 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzo thiazoline-6-sulphonic acid) (ABTS), and hydroxyl free radical (OH⁻) scavenging activities, ferric reducing antioxidant power (FRAP), and anti-microbial activity than traditional solvents. 50% ethanol/methanol were the most effective extraction solvent for inhibition of α-glucosidase. The results of multivariate analysis highlighted the influence of solvents on the TPC and biological activities of MCLs extracts. These findings clearly indicate that DESs can be used as the most effective solvents for extraction of phenolic compounds from MCLs extracts. The results suggest that the MCLs can be a promising source enriched with bio-active constituents for application in the pharmaceutical industries.