Optimization of Phytochemical-Rich Citrus maxima Albedo Extract Using Response Surface Methodology

In the present study, response surface methodology (RSM) and Box-Behnken design (BBD) were employed to optimize the conditions for the extraction of C. maxima albedo from agricultural waste, to obtain notable phytochemicals. Ethanol concentration, extraction temperature, and extraction time were included as key factors contributing to the extraction. The results showed that the optimum extraction condition for C. maxima albedo was 50% (v/v) aqueous ethanol at 30 °C for 4 h, which provided total phenolic contents and total flavonoid contents at 15.79 mg of gallic equivalent/g dry weight (DW) and 4.50 mg of quercetin equivalent/g DW, respectively. Considerable amounts of hesperidin and naringenin at 161.03 and 3430.41 µg/g DW, respectively, were detected in the optimized extract using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). The extract was later subjected to a test for its enzyme-inhibitory activities against key enzymes relevant to Alzheimer's disease (AD), obesity, and diabetes as well as for its mutagenicity potential. Among enzyme inhibitory activities, the extract showed the highest inhibitory strength against β-secretase (BACE-1), which is a drug target for AD treatment. The extract was also devoid of mutagenicity properties. Overall, this study demonstrated a simple and optimal extraction procedure for C. maxima albedo with a significant quantity of phytochemicals, health benefits, and genome safety.