Secoiridoids and lignans from the leaves of Diospyros kaki Thunb. with antioxidant and neuroprotective activities

Abstract

The leaves of persimmon (LP) have been used for centuries in China, Korea and Japan as a delicate, pleasant beverage and an effective herbal remedy. Phytochemical investigations of LP have resulted in the discovery of two new secoiridoid glucosides, named persimmonoid A and B (1–2), together with ten known ones. Antioxidant and neuroprotective assays of all compounds were carried out, and compounds (+)-medioresinol (5), (+)-pinoresinol (7), (+)-pinoresinol-β-D-glucoside (10) and (−)-(7′S,8S,8′R)-4,4′-dihydroxy-3,3′,5,5′-tetramethoxy-7′,9-epoxylignan-9′-ol-7-one (12) were found to exhibit significant activity in the ABTS radical scavenging assay, while compounds (+)-syringaresinol (6), (+)-pinoresinol (7) and (+)-isolariciresinol (11) displayed stronger activity than the positive control in the FRAP assay. In addition, some of these compounds showed statistically significant neuroprotective activities. The HPLC-QQQ-MS/MS method was successfully applied to quantify twelve compounds from LP and fruits of persimmon (FP). The bioactive studies supported LP potential for development as a new antioxidant and neuroprotective functional food.

Keywords

• Diospyros kaki Thunb
• Secoiridoids
• Lignans
• Antioxidant activity
• Neuroprotective activity