Investigation of antibrowning activity of pine needle (Cedrus deodara) extract with fresh-cut apple slice model and identification of the primary active components

Abstract

Cedrus deodara is a large evergreen tree of the family Pinaceae and widely distributed to the west of Himalayas. Its pine needles are consumed as a traditional food and perceived as a valuable source for bioactive compounds. A recent study has demonstrated Cedrus deodara pine needle extract (CDE) can inactivate tyrosinase. However, possible action mechanism and application of the extract have not been elucidated. In the present study, the application of CDE in food industry was explored using a fresh-cut apple slice model. Through evaluating the variation in a*, b* and L* values, the browning extent of apple slices was found to be inhibited by CDE. Moreover, in order to explore the antibrowning mechanism, we investigated the antioxidant and antibrowning capacities, total phenolic and flavonoid contents and the major bioactive constituents of the extract. It was found CDE showed strong antioxidant activity to scavenge ABTS (SC50, 24.33 μg/mL) and DPPH (SC50, 35.94 μg/mL) radicals, inhibited monophenolase (IC50, 0.76 ± 0.08 mg/mL) and diphenolase (IC50, 1.01 ± 0.09 mg/mL) activities and contained high content of phenolics (76.39 ± 2.27 mg gallic acid equivalent/g extract) and flavonoids (33.23 ± 3.25 mg rutin equivalent/g extract). Furthermore, according to the bioassay-guided isolation and the analysis of high-performance liquid chromatography–mass spectrometry and nuclear magnetic resonance, methylconiferin and ferulic acid-β-d-glucoside were determined to be the main active compounds. The current results provided the possible antibrowning mechanism of CDE and confirmed C. deodara pine needles might be a natural resource for preparing antibrowning agents of vegetables and fruits in food industry.