Characterization of phenolic compounds and anti-acetylcholinase activity of coconut shells

Abstract

Free phenolics (F), soluble esterified (SE) and glycosylated (SG) bound phenolics, insoluble (IS), insoluble esterificated (ISE) and glycosylated (ISG) bound phenolics were extracted from coconut mesocarp (CM) and coconut endocarp (CE) by acid-alkali treatment, respectively. Results of Folin-ciocalteu method and HPLC-MS quantitative analysis of 22 typical phenolic compounds showed that the distribution and content of phenolic compounds in a coconut shell were varied with different parts and components. The total phenolic content (TPC) of CM was significantly higher than that of CE. The TPC of soluble phenolics in coconut shell was significantly higher than that of insoluble phenolics. Antioxidant activities by FRAP method and acetylcholinesterase (AChE) inhibition activities of the twelve components were highly correlated with the TPC (RFRAP/TPC = 0.9938, Ranti-AChE/TPC = 0.9616). The correlation between their anti-AChE activities and FRAP values of 11 flavonoids (R = 0.9221) was higher than that of 11 phenolic acids (R = 0.6018). Among identified phenolics, quercetin (71.25%), kaempferol (64.84%) and gallic acid (57.32%) had higher anti-AChE activities, while catechin (– 6.53%), chlorogenic acid (– 9.40%) and epicatechin (– 22.40%) had negative effects. Among the twelve components, CM-SE, F and IS had high polyphenol utilization potential, while CM-SE, IS and CE-SE had high anti-AChE utilization potential. Phenolic components are related to anti-AChE activities, which might attract researchers to further explore the neuroprotective effect of coconut shell extracts.