Combination of Plackett-Burman and Box–Behnken designs in optimization for integrated enzyme- and microwave-assisted co-extraction of polysaccharides and polyphenols from mangosteen peels

Mangosteen peels, a waste constituting more than 50% of the fruit weight, contain high amounts of functional compounds such as polysaccharides and polyphenols. Their recovery could provide added value for the plant. Hence, this study investigated the optimization of an integrated enzyme- and microwave-assisted process for the simultaneous extraction of these two components from mangosteen peels (Garcinia mangostana Linn). The study employed a two-step optimization approach, where significant factors were first identified using Plackett–Burman design (PBD) with five factors, and the optimal levels of the significant factors were then determined using Box– Behnken design (BBD). The results found that three factors had significant effects, and their optimal conditions included a pH of 5.8, a buffer-to-solid ratio of 71 mL/g, and a microwave time of 80 s. Under these optimized conditions, the yields of polysaccharides and polyphenols were 30.95% and 85.96 mg gallic acid equivalent (GAE)/g, respectively. The results demonstrated that the integrated microwave- and enzyme-assisted extraction method is an efficient and environmentally friendly method for the extraction of polysaccharides and polyphenols from mangosteen peels. Moreover, the combination of PBD and BBD formed a powerful optimization tool that led to time-efficient and effective process optimization.