Abstract

In this study, the effects of some important factors such as concentration of solvent, material ratio, temperature and time was investigated on the contents of flavonoids present in the mulberry leaves. Central composite rotatable design (CCRD) was performed to optimize the extraction parameters for assessing maximum yield of total flavonoid content (TFC) from mulberry leaves. The range of the variables, namely methanol concentration (20 to 100%, v/v), extraction temperature (40 to 80°C), material/solvent ratio (1:5 to 1:25) and extraction time (1 to 3 h) were identified by a first set of single factor experiments. The actual values of the independent variables implicit at five levels were selected based on the results of single factor experiments. The optimum conditions for extraction of TFC were found to be at methanol concentration 81.36%, extraction temperature 36.4°C, extraction time 2.37 h and material/solvent ratio 1:15. Under these optimized conditions maximum yield of TFC was 3.36 mg/g dry weight, which was in close agreement with predicated values (3.382 mg/g dry weight), in consequence representing the suitability of the models developed in optimizing the extraction conditions.

Key words: Total flavonoids, mulberry (Morus alba L.) leaves, models, central composite rotatable design.