Keywords: Ananas comosus peels; response surface methodology; optimization; ultrasonic-assisted extraction

Abstract

Pineapple (Ananas comosus) peels contain various phytochemicals, such as antioxidants and polyphenols. In this study, ultrasound-assisted extraction (UAE) was applied to optimise the extraction of A. comosus peels by using the Central Composite Design (CCD). The extraction of ground A. comosus peels with aqueous methanol was optimised for factors including extraction time and solvent: sample and methanol: water ratios in order to identify the responding percentage yield (PY), total phenolic content (TPC), total flavonoid content (TFC), and free radicals scavenging activity by DPPH. This study also compared the extraction via Soxhlet extraction for all three responses. The UAE extracts, under conditions E18 and E20, exhibited 50% scavenging activity of DPPH free radicals with a corresponding SC50 value of 549.535±17.277 and 669.744±0.955 μg/mL, respectively. Meanwhile, Soxhlet extraction outcomes revealed that only the chloroform extract gave an SC50 value of 631.238±3.126 μg/mL. Additionally, the UAE and Soxhlet-generated extracts employed in the antibacterial assay were weakly active against Gram-positive and Gram-negative bacteria, respectively. Henceforth, this study highlights the A. comosus peels as a good source of different minor compounds, warranting further exploration using the UAE method.