Unraveling the active hypoglycemic agent trigonelline in Balanites aegyptiaca date fruit using metabolite fingerprinting by NMR

Trigonelline (3-carboxy-1-methyl pyridinium) was identified as a relevant bioactivity and taste imparting component in Balanites aegyptiaca fruit, using H-1 NMR of crude extracts without any fractionation or isolation step. The structural integrity of trigonelline was established within the extract matrix via H-1 NMR, H-1-H-1 COSY, HMQC and HMBC and by comparison with authentic standard. A quantitative H-1 NMR method (qHNMR) was used to determine trigonelline concentrations in the peel and pulp of B. aegyptiaca fruit of 8 and 13 mg g(-1), respectively. Trigonelline so far has not been reported from B. aegyptiaca or its genus as it easily escapes LC-MS based detection. Its discovery provides novel insight into the balanite fruits antidiabetic properties as the compound is known for a pronounced hypoglycemic effect. In addition, it is likely to impart the perceptible bitter taste portion to balanites sweet bitter taste. UPLC-MS of the crude extract additionally revealed the fruit flavonoid pattern showing quercetin/isorhamnetin flavonol conjugates in addition to epicatechin, the latter being present at much lower levels. (C) 2015 Elsevier B.V. All rights reserved.