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Ananas comosus (L.) Merr is one of many commercially popular fruits in the cannery food industry that contributes to the increasingly mounting agro-industrial waste. In this study, a four−factor−three−level Box−Behnken design (BBD) that comprised of sonication time (A), solvent ratio (B), amplitude (C) and liquid−solid ratio (D) for the ultrasound−assisted extraction (UAE) of pineapple peels (PP) was utilized to optimize the yield of total phenolic content (TPC). Under an optimized UAE condition [5 min; 50 % of ethanol: water; 65 % of amplitude; 35:1 mL/g of liquid−solid ratio], the highest TPC from PP of 708.10 mg gallic acid equivalent (GAE)/g DW was achieved. Antioxidant capacity analysis of PP revealed a high total flavonoid content (TFC) with the IC50 for 2,2−diphenyl−1−picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) of 1146.86 ± 11.83 mg QE/g, 11.83 mg/mL and 1578.07 ± 25.96 µM Fe (II)/100g, respectively. High-performance liquid chromatography (HPLC) analysis revealed that the major flavonoid in the phenolic profile of PP extracts being catechin followed by quercetin and gallic acid. The UAE of PP extracts exhibited higher TPC than known conventional extraction techniques, thus indicating its efficacy to recover satisfactory quantities of phenolics in PP under optimized conditions.

The research was carried out to synthesize a stable kojic acid (KA) encapsulated nanoemulsion as a whitening agent for topical skin usage. In this study, the oil-in-water (O/W) KA nanoemulsion was formulated using integrated low and high energy methods that combined ultrasonic and hot temperature inversion methods. Several different combinations of parameters were screened, viz. xanthan gum amount (1.0 to 2.0 g), kojic acid (KA) amount (0.5 to 1.5 g), and surfactant-to-water ratio (1:10.75 to 1:4.875), to prepare a stable KA nanoemulsion. The identified best parameters to design the O/W KA nanoemulsion were then subjected to different stability tests: storage and pH stability (freeze-thaw and centrifugal tests). Results revealed that the Trial 6 formulation, with the highest ratio of Tween 80 to water (1:4.875 v/v), yielded the best polydispersity index at 0.255 ± 0.006 with an average particle size of 90.57 ± 1.401 nm. The formulation retained the recommended pH range (pH 4.95–5.18) for topical skin applications within six-week storage under room condition. The nanoemulsions were also kinetically stable as proven by the absence of phase separation after the centrifugation, freeze-thaw cycle, and storage temperature (2 and 25 °C) tests, except at the 37 °C three-week extended storage. The results collectively showed that the formulated O/W KA nanoemulsion is suitable for topical application on human skin.

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