Optimization of microwave-assisted extraction of anthocyanins from purple corn (Zea mays L.) cob and identification with HPLC–MS

A Box–Behnken design was used to obtain the optimal conditions of microwave-assisted extraction (MAE). The effects of operating conditions, such as extraction time, solid–liquid ratio, and microwave irradiation power, on the extraction yield of anthocyanins were studied through a response surface methodology (RSM). The highest total anthocyainin content (TAC) from purple corn cob (185.1 mg/100 g) was obtained at an extraction time of 19 min, a solid–liquid ratio of 1:20, and a microwave irradiation power of 555 W. Six major kinds of anthocyanins were detected and identified as cyanidin-3-glucoside, pelargonidin-3-glucoside, peonidin-3-glucoside, and their respective malonated counterparts. In comparison with the conventional solvent extraction, MAE was highly efficient and rapid in extracting anthocyanins from Chinese purple corn cob.Industrial relevanceIn the last decades, the interest in anthocyanin pigments has increased because of their possible utilization as natural food colorants and especially as antioxidant and anti-inflammatory agents. Purple corn cob was the byproduct during the corn processing. Purple corn cob is dark purple to almost black color due to its high content of anthocyanins, which makes this byproduct a good source of anthocyanins.