Background and Objectives: Melinjo is a tree native to Indonesia. Melinjo seed extract (MSE) contains gnetin C, gnetin L, and gnemonosides as resveratrol dimer derivatives. The seeds are particularly rich in gnetin C. In human clinical trials, relatively high-dose intake of MSE reportedly decreased serum uric acid. We examined the safety and effects of long-term regular-dose MSE intake to decrease serum uric acid, and the relationship with serum concentrations of MSE derivatives.
Methods and Study Design: Subjects with serum uric acid concentrations of 6.0-6.9 mg/dL were divided into 4 groups receiving placebo or MSE at 100, 200, or 300 mg/day for 12 weeks. Subjects with uric acid concentrations of 7.0-7.9 mg/dL took 300 mg of MSE. Serum MSE derivatives at 12 weeks were measured in subjects who took MSE at 300 mg/day.
Results: Ninety-eight men participated and 11 of those participants dropped out of this trial.No significant adverse events were detected, whereas no significant serum uric acid changes were detected. Serum concentrations of gnetin C monoglucuronide and total gnetin C (gnetin C+gnetin C monoglucuronide), representing major derivatives of MSE, tended to correlate with decreased serum uric acid concentrations. The subjects with total gnetin C ≥ 200 ng/mL showed a decrease in the serum uric acid concentration compared with those with total gnetin C < 200 ng/mL in the group with uric acid ≥ 7.0 mg/dL at week 0.
Conclusions: Regular-dose MSE can be safely ingested, and high serum gnetin C concentrations might decrease serum uric acid.