Quantification of phytochemical and antioxidant properties of aqueous apple extracts from the high atlas mountains in Morocco and their anti-inflammatory effect on Wistar rats

Abstract

Apples are a valuable source of health-promoting polyphenols. However, a considerable variation in the polyphenol contents and bioactivities may exist among different apples from different origins. As the apples derived from traditional agriculture in the Moroccan High Atlas Mountains (above 2000 m of altitude) are less explored. This study aimed to investigate the polyphenol contents, antioxidant and anti-inflammatory activities of aqueous extracts derived from five varieties of apples from the High Atlas Mountains in Morocco compared to two imported European varieties of apples. The content of phenol acids, flavonoids, tannins, and reducing sugars were spectrophotometrically measured. Ferric reducing antioxidant power (FRAP), radical scavenging activity (RSA), and total antioxidant capacity (TAC) were assessed in vitro. The anti-inflammatory activity was conducted using paw edema induced by sub-plantar injection of formalin (0.05 mL, 4%) in rats. The results showed that local apples, particularly the Imilchil extract, contained the highest content of polyphenols (9.11 ± 0.36 GAE mg/gE), flavonoids (7.59 ± 0.23 RE mg/gE), and tannins (2.94 ± 0.05 CE mg/gE) but lower content of reducing sugars. Among all the tested extracts, Imilchil also exhibited the highest antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl RSA (IC50= 1.12 ± 0.02 mg/mL), FRAP (110.55 ± 1.55 Fe2+E mMol/gE) and TAC (731.48 ± 3.02 AAE µg/gE) when compared with imported apples (Alpe and Golden), that have the lowest antioxidant activities in RSA (IC50 3.46 ± 0.12 and 3.92 ± 0.10 mg/ml), FRAP (18.30 ±.08 and 21.27 ± 0.99 Fe2+E mMol/gE) and TAC assays (133.22 ± 6.42 and 225.06 ± 2.88 AAE µg/gE), respectively. The administration of a single dose (500 mg/kg BW) of local apple extracts significantly inhibited about 54.77% of paw edema, while the imported apples produced about 30.60%. It is concluded that apples from the Moroccan High Atlas Mountains could be a rich source of natural polyphenols with anti-inflammatory and antioxidant potentialities.