A green and novel strategy based on CO2 -responsive surfactant-functionalized multi- walled carbon nanotubes with microwave- ultrasound assistant to improve extraction and enrichment of phytochemicals from plant waste

Abstract

In this study, a noval method was developed based on CO2 -responsive surfactant-functionalized multi-walled carbon nanotubes with microwave -ultrasound assistance extraction (CRS-MWN-MUAE) for obtain value-added compounds from plant waste. The single-factor experiments were applied to obtain the best experiment conditions: ultrasound power of 600 W, ultrasound time of 25 min, microwave time of 20 min, microwave power of 500 W, solid-to-liquid ratio of 20 mg/mL, and multi-walled carbon nanotubes (MWN) concentration of 4 g/L. The representative flavonoid and stilbene from pigeon pea leaves were orientin and cajaninstilbenes acid (CSA). The representative triterpenoid from cili fruits was roxburic acid. The representative flavonoid from cili leaves was quercetin. The representative anthocyanin from blackcurrant fruits was cyanidin 3-O-glucoside (C3G). The representative organic acid from blackcurrant leaves was chlorogenic acid. The orientin, CSA, roxburic acid, quercetin, C3G, chlorogenic acid extraction yields were: 4.42 mg/g, 9.43 mg/g, 1.56 mg/g, 0.15 mg/g, 2.24 mg/g, and 1.07 mg/g. Under these conditions, the solvent system possessed higher efficiencies from various plant wastes compared with other extraction method. The contents of target compounds have increased 1.1–20 folds. Meanwhile, the green surfactants could be recycled and achieved no significant loss in six operation cycles. Moreover, density functional theory and molecular dynamics simulation investigated the surfactant could be well compatible with target compounds because of the weak interactions among moleculars. Thus, the method was a green, efficient, novel, and ecofriendly extraction method for extracting and enriching high value-added compounds from cili, pigeon pea, and blackcurrant wastes.