A green process for extracting and purifying coconut mesocarp polyphenols

Coconut, as one of the main tropical economic crops, has high yield and high demand. Coconut mesocarp (CM) is the main waste in coconut production, causing resource waste and bulk pollution issues. In this study, a green process for extracting and purifying CM polyphenols was developed, which was beneficial for turning waste into treasure and saving resources. The process included a series of steam explosion (SE) assisted alkali extraction methods for the total phenolic content (TPC) of total phenols (CTP) and insoluble phenols (CIP) in CM and purification process of macroporous resin. These results showed after SE treatment at 123 °C for 5 min, the TPC of CTP and CIP increased to 558.57 mg GAE/g dw and 280.67 mg GAE/g dw, which was higher 9% and 17.8% than the untreated sample, respectively. After purification with LX-83, the TPC of purified CTP (P-CTP) and CIP (P-CIP) increased to 773.16 mg GAE/g dw and 542.83 mg GAE/g dw. Both Langmuir and Freundlich adsorption models could be used to describe the adsorption behaviors of CTP and CIP. They were influenced by multiple factors and belonged to a pseudo second-order kinetic model. Subsequently, the main compounds in P-CTP and P-CIP were the abundant catechin, epicatechin, caffeic acid, p-coumaric acid and 4-hydroxybenzoic acid by HPLC-MS analysis. These results provided a basis for the green extraction and purification process of CM polyphenols.