Quantification of nitropropanoyl glucosides in karaka nuts before and after treatment

Abstract

A high performance liquid chromatography (HPLC) method was developed to assay nitropropanoyl glucosides in the nuts of karaka (Corynocarpus laevigatus) a traditional food of New Zealand Māori. Levels of glucosides, measured as 3-nitropropanoic acid, ranged from 50.25 to 138.62gkg−1 (5.0–13.9% w/w) and were highest in nuts from unripe drupes; these levels are higher than any previously reported. Other parts of the drupe also contained nitropropanoyl glucosides but at lower levels than the nut. Treatment procedures to remove the glucosides from the nuts varied in their efficacy with soxhlet extraction removing 98.7% and prolonged boiling and cold water extraction both removing 96%. These findings confirm the traditional methods for preparation of these nuts for consumption.