In Vitro Antioxidant And Alpha-Glucosidase Inhibitory Activities Of Fruit Extracts From Seven Species Of Citrus
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Date
2018-08
Authors
Henrietta, Ikwunne Helen
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Publisher
Universiti Sains Malaysia
Abstract
The in vitro α-glucosidase inhibitory and antioxidant activities, total phenolic and vitamin C contents of the pure juices (squeezed from the pulps), peel and pulp extracts from siix Citrus fruits that are grown in Malaysia, which are Citrus aurantifolia, Citrus grandis var. Tambun (PO52) and var. Penang Merah (PO5), Citrus hystrix, Citrus latifolia, and Citrus madurensis together with Citrus limon from Spain were determined in this comparative study. This is owing to the fact that these Citrus species that can be found in Malaysia has never been comparatively studied. The peels are mostly studied while the pulps and the juices are given less attention. The fresh and dried peel and pulp samples were extracted using methanol, ethanol and distilled water while 80% methanol was used for the extraction of crude extracts from dried peels and pulps. The result obtained from 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay revealed the highest free radical scavenging activity (96.14 ± 0.30%) of the methanol extract of dried peel of C. limon (at 100 mg/mL). The methanol extract of dried peel (at 100 mg/mL) and the juice of C. grandis var. Tambun (PO52) shared the highest ferric-reducing antioxidant power (FRAP) at 85.03 ± 6.32% and 84.29 ± 0.40%, respectively. The ethanol extract of fresh peel of C. grandis var. Penang Merah (PO5) exhibited the highest metal chelating activity at 98.85 ± 0.82%. Among the juices, the juice of C. grandis var. Tambun (PO52) gave the highest total phenolic content (TPC) of 14956.34± 152.65 μg gallic acid equivalent (GAE)/g juice. The distilled water extract of dried peel of C. limon gave the highest TPC at 33148.87 ± 124.46 μg GAE/g fresh weight of sample. The highest vitamin C content was quantified from the juice of C. limon (731.88 ± 0.49 μg ascorbic acid equivalent (AAE)/g juice). The results also showed the decrease in the antioxidant activities, TPC and vitamin C contents of the juices during storage. All pure juices excluding the juices of C. grandis gave high α-glucosidase inhibitory activities and the highest activity was measured from the juice of C. limon (96.51 ± 0.26%). A moderate correlation between FRAP and DPPH activities of all extracts was observed with r2 of 0.5943 that is significant at p < 0.001. The correlation between TPC and FRAP was the highest in comparison with the other tested activities at 0.5649 (p < 0.001). Vitamin C content was found to be highly correlated with α-glucosidase inhibitory activity with r2 of 0.5164 (p < 0.001). When extracts from different sample matrices were separately analysed, the DPPH activities and TPC of fresh peel extracts were found to have the highest correlation at 0.7947 (p < 0.001). Vitamin C contents of the fresh pulp of extracts and their DPPH activities was also highly correlated at 0.6810 (p <0.001).
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Medicine