Optimisation of extraction of piceatannol from Rhodomyrtus tomentosa seeds using response surface methodology

• Distribution of phenolic compounds in the sim fruit was analysed for the first time.
• Most (94.20%) of the fruit total piceatannol content occurred in the seeds.
• Others stilbenes and ellagitannins predominated in the seeds of the sim fruit.
• Most of the anthocyanins and flavonols were in the skin.
• The conditions for piceatannol extraction from the sim seeds were optimised.

The extraction of piceatannol from the sim fruit (Rhodomyrtus tomentosa) was optimised. Firstly, the piceatannol content was determined in the different parts of the fruit (skin, pulp, and seed) and indicated that 94.20% of the piceatannol content was associated to the seeds, which were chosen as starting material to optimise the piceatannol extraction. A second-order polynomial model with three important variables (ethanol concentration, temperature and extraction time) was used. A rotatable central composite design consisting of 21 experimental runs with three replicates at the centre point was applied to describe the experimental data, i.e. the sim seed apparent piceatannol content. The experimental results fitted well to the model (R2 = 0.9647). The optimised conditions were 78.8% ethanol, 85.3 °C and an extraction time of 78.8 min. Four extractions were performed in parallel at the optimal conditions to validate the model. The experimental value agreed with the predicted value (p < 0.05).