Abstract The aim of this study was to investigate the total flavonoid content (TFC), vitamin C content, and the anti-hyperglycemic activities of pomelo peel extract (PPE) from the flavedo and albedo of two pomelo cultivars namely Long Co Co and Thanh Kieu in the Mekong Delta of Vietnam. Thanh Kieu PPE possessed the highest TFC of 11.18 ± 0.14 mg/100 g from the albedo while the highest vitamin C content was found in its flavedo (47.74 ± 0.34 mg/100 g). PPE from the flavedo induced the mortality after 3-4 h of oral administration at a dosage of 5000 mg/kg. In the contrast, PPE from the albedo was considered a non-toxic extract. Albedo PPE from two cultivars was observed to attenuate the blood glucose level of alloxan-hyperglycemia induced mice (from roughly 350 mg/dL to 150 mg/dL) and there was no significant difference in the anti-hyperglycemic efficacy between albedo PPE and chemical drug (Glucophage). This finding showed potential in developing new functional food products or pharmaceutical alternatives from pomelo peels (an agro-waste) for anti-hyperglycemia.

Abstract Pomelo peels have been well known as a valuable source of phenolic compounds mainly flavonoids. In this study, the influences of extraction conditions of three extraction methods on the polyphenols yield, flavonoids yield, and antioxidant activity of resulting pomelo flavedo extract (PFE) were evaluated. As a result, the suitable process parameters for the ultrasound assisted extraction were selected at an applied power of 120 W, the temperature of 60 oC for 20 min. Meanwhile, the microwave assisted extraction was operated at an applied power of 150 W for 25 min and the Soxhlet extraction was carried out up to 4 reflux cycles (35 min per cycle) at 80 oC. Among three methods, the microwave assisted extraction was considered as the most efficient method to obtain the high yield of polyphenols (80.56%) and flavonoids (86.58%). Naringin and hesperidin determined by high-performance liquid chromatography showed the value of 64.42 ± 2.90 mg/g DW and 0.97 ± 0.02 mg/g DW, respectively. The PFE extracted by the microwave assisted extraction could be a potent nutraceutical in further application on food or pharmaceutical industries.

Abstract Citrus peel extract has been observed with many beneficial-promoting effects. Pomelo (Citrus grandis (L) Osbeck) peel extracts (PPE) from the flavedo and albedo of two varieties namely Long Co Co and Thanh Kieu were investigated. In this study, the qualitative analysis indicated the presence of phytochemical groups including alkaloids, flavonoids, saponins, and tannin in the PPE from the flavedo and albedo. The PPE from the Thanh Kieu flavedo was found to possess the highest antioxidant activity at the EC50 values of 60.89 ± 0.31 µg/mL, 60.69 ± 0.21 µg/mL, and 24.16±0.06 µg/mL for DPPH, ABTS, and FRAP assay. However, the Long Co Co albedo- PPE induced better inhibitory effect against α-amylase (EC 232-560-9) and α-glucosidase (EC 232-604-7) with respect to EC50 values of 3.59 ± 0.02 mg/mL and 80.77 ± 0.34 µg/mL. This result suggested potential in the anti-hyperglycemic effect of pomelo peel extract from the flavedo and albedo that can serve as a nutraceutical in food and pharmaceutical industries.