Pomelo fruitlets have the potential for extracting cellulose. This study aimed to investigate characterization and functionality of cellulose extracted from pomelo fruitlets by different extraction methods. Cellulose extracted by acidic-alkaline hydrogen peroxide hydrolysis (CAA), alkaline hydrogen peroxide hydrolysis (CA), and ultrasonic assisted alkaline hydrogen peroxide hydrolysis (CUA) were prepared from pomelo fruitlets. The results showed that cellulose CUA had higher yield and purity with higher crystallinity and smaller particle size than those of CAA or CA (p < 0.05). Specifically, the yield of CUA was 82.75% higher than that of CAA, and purity was increased by 26.42%. Additionally, water- and oil-holding capacities of CUA were superior to those of CAA or CA, increasing by 13–23% and 10–18%, respectively. The improvement of water- and oil-holding capacities were highly related to its smaller particle size with increased surface area. The results suggested that ultrasonic assisted alkaline hydrogen peroxide hydrolysis is a promising and efficient method to prepare high-purity cellulose from pomelo fruitlets, and this cellulose is expected to be a food stabilizer and pharmaceutical additive.

In this study, flavonoids were extracted from pomelo peels and naringin was isolated from the flavonoid extract. The effects of extraction parameters, namely, ethanol concentration, solid-to-liquid ratio, and extraction time, on the yield of flavonoids extracted from pomelo peels were analyzed according to the Box-Behnken design of response surface methodology. The experimental conditions for flavonoid extraction were optimized, and naringin was separated from the extracted flavonoids using Sephadex LH-20 column chromatography. Experimental results showed that the influence of factors on the extraction rate of flavonoids from pomelo peels was in the order of ethanol concentration > solid-to-liquid ratio > extraction time, and the optimal extraction parameters were 85% ethanol concentration, 1:20 solid-to-liquid ratio, and 4-h extraction time for extracting flavonoids from pomelo peels. Under these conditions, the yield of flavonoids was 6.07 ± 0.06 mg/g. After three times of extraction, the flavonoid extraction rate reached 96.55%, and the residual naringin in the pomelo peels was 0.017 mg/g, at which point the bitterness in the pomelo peels disappeared. Two components, namely, PF1 and PF2, were separated from the crude flavonoid of pomelo peels through Sephadex LH20 column chromatography. PF2 was identified as naringin by high-performance liquid chromatography tandem mass spectrometry, with a purity of 95.7 ± 0.23%. Both flavonoids and PF2 exhibited good in vitro radicals scavenging activities on DPPH, ABTS, superoxide anion and hydroxyl.

• PPDF significantly reduced weight gain and visceral fat accumulation of obese mice. • PPDF significantly alleviated HFD-induced dyslipidemia. • PPDF ameliorated HFD-induced gut microbiota dysbiosis. • PPDF prevented mice obesity via gut microbiota regulation.